Editing Delirium

{{Short description|Severe confusion that develops quickly, and often fluctuates in intensity}}
{{About|the mental state and medical condition}}
{{cs1 config|name-list-style=vanc|display-authors=6}} 
{{Infobox medical condition (new)
| name            = Delirium
| specialty       = [[Intensive care medicine]], [[Neurology]], [[Psychiatry]], [[Geriatrics]] 
| caption         = Delirium is an acute disturbance of cognition
| pronounce       =
| symptoms        = [[Psychomotor agitation|Agitation]], [[confusion]], [[drowsiness]], [[hallucinations]], [[delusions]], [[memory problems]]
| complications   =
| onset           = Any age, but more often in people aged 65 and above
| duration        = Days to weeks, sometimes months (several hours when caused by [[anticholinergic]] medications, like [[dicyclomine]], [[diphenhydramine]] ([[Benadryl]]), [[doxylamine]], [[promethazine]])
| types           = Hyperactive, hypoactive, mixed level of activity
| causes          = Inconclusive
| risks           = [[Infection]], chronic health problems, certain medications, [[neurological problems]], [[sleep deprivation]], [[surgery]]
| diagnosis       =
| differential    = [[Dementia]]
| prevention      =
| treatment       = Treating underlying cause, symptomatic management with medication
| medication      = Depending on the underlying cause
| prognosis       =
| frequency       =
| deaths          =
| alt             =
}}

<!-- Definition and symptoms -->
'''Delirium''' (formerly '''acute confusional state''', an ambiguous term that is now discouraged)<ref name="slooter2020">{{cite journal | vauthors = Slooter AJ, Otte WM, Devlin JW, Arora RC, Bleck TP, Claassen J, Duprey MS, Ely EW, Kaplan PW, Latronico N, Morandi A, Neufeld KJ, Sharshar T, MacLullich AM, Stevens RD | title = Updated nomenclature of delirium and acute encephalopathy: statement of ten Societies | journal = Intensive Care Medicine | volume = 46 | issue = 5 | pages = 1020–1022 | date = May 2020 | pmid = 32055887 | pmc = 7210231 | doi = 10.1007/s00134-019-05907-4 }}</ref> is a specific state of acute confusion attributable to the direct [[physiological]] consequence of a medical condition, effects of a psychoactive substance, or multiple causes, which usually develops over the course of hours to days.<ref name="Delirium">{{cite journal | vauthors = Wilson JE, Mart MF, Cunningham C, Shehabi Y, Girard TD, MacLullich AM, Slooter AJ, Ely EW | title = Delirium | journal = Nature Reviews. Disease Primers | volume = 6 | issue = 1 | pages = 90 | date = November 2020 | pmid = 33184265 | pmc = 9012267 | doi = 10.1038/s41572-020-00223-4 | s2cid = 226302415 | doi-access = free }}</ref><ref name="DSM-5-TR">{{Cite web |title=Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR™) |url=https://www.appi.org/products/dsm |website=American Psychiatric Association |access-date=April 18, 2022 |archive-date=April 22, 2022 |archive-url=https://web.archive.org/web/20220422004848/https://www.appi.org/products/dsm |url-status=live }}</ref> As a [[syndrome]], delirium presents with disturbances in attention, awareness, and higher-order cognition. People with delirium may experience other neuropsychiatric disturbances including changes in psychomotor activity (e.g., [[psychomotor agitation|hyperactive]], [[psychomotor retardation|hypoactive]], or mixed level of activity), disrupted [[sleep-wake cycle]], emotional disturbances, disturbances of consciousness, or altered state of consciousness, as well as perceptual disturbances (e.g., [[hallucination]]s and [[delusion]]s), although these features are not required for diagnosis.

<!-- Cause -->
Diagnostically, delirium encompasses both the syndrome of acute confusion and its underlying [[Organic brain syndrome|organic]] process<ref name="DSM-5-TR" /> known as an [[encephalopathy|acute encephalopathy]].<ref name="slooter2020"/> The cause of delirium may be either a disease process ''inside'' the brain or a process ''outside'' the brain that nonetheless affects the brain. Delirium may be the result of an underlying medical condition (e.g., infection or [[Hypoxia (medical)|hypoxia]]), side effect of a medication such as [[diphenhydramine]], [[promethazine]], and [[dicyclomine]], substance intoxication (e.g., opioids or [[Deliriants|hallucinogenic deliriants]]), substance withdrawal (e.g., [[alcohol (drug)|alcohol]] or [[sedative]]s), or from multiple factors affecting one's overall health (e.g., malnutrition, pain, etc.). In contrast, the emotional and behavioral features due to primary psychiatric disorders (e.g., as in [[schizophrenia]], [[bipolar disorder]]) do not meet the diagnostic criteria for 'delirium'.<ref name="Delirium"/>

<!-- Diagnosis -->
Delirium may be difficult to diagnose without first establishing a person's usual mental function or 'cognitive baseline'. Delirium may be confused with multiple [[psychiatric disorders]] or chronic [[organic brain syndrome]]s because of many overlapping signs and [[symptoms]] in common with [[dementia]], [[mood disorder|depression]], [[psychosis]], etc.<ref>{{cite journal | vauthors = Gleason OC | title = Delirium | journal = American Family Physician | volume = 67 | issue = 5 | pages = 1027–1034 | date = March 2003 | pmid = 12643363 | url = http://www.aafp.org/afp/2003/0301/p1027.html | url-status = live | archive-url = https://web.archive.org/web/20110606072937/http://www.aafp.org/afp/2003/0301/p1027.html | archive-date = 2011-06-06 }}</ref><ref name="pseudodelirium">{{cite journal | vauthors = Wilson JE, Andrews P, Ainsworth A, Roy K, Ely EW, Oldham MA | title = Pseudodelirium: Psychiatric Conditions to Consider on the Differential for Delirium | journal = The Journal of Neuropsychiatry and Clinical Neurosciences | volume = 33 | issue = 4 | pages = 356–364 | date = Fall 2021 | pmid = 34392693 | pmc = 8929410 | doi = 10.1176/appi.neuropsych.20120316 }}</ref> Delirium may occur in persons with existing mental illness, baseline intellectual disability, or dementia, entirely unrelated to any of these conditions.  Delirium is often confused with [[schizophrenia]], [[psychosis]], organic brain syndromes, and more, because of similar signs and symptoms of these disorders.

<!-- Treatment and epidemiology -->
Treatment of delirium requires identifying and managing the underlying causes, managing delirium symptoms, and reducing the risk of complications.<ref name = SIGN>{{Cite web|title=SIGN 157 Delirium|url=https://www.sign.ac.uk/sign-157-delirium|website=www.sign.ac.uk|access-date=2020-05-15|archive-date=2022-12-06|archive-url=https://web.archive.org/web/20221206065513/https://www.sign.ac.uk/sign-157-delirium|url-status=live}}</ref> In some cases, temporary or symptomatic treatments are used to comfort the person or to facilitate other care (e.g., preventing people from pulling out a breathing tube). [[Antipsychotics]] are not supported for the treatment or prevention of delirium among those who are in hospital; however, they may be used in cases where a person has distressing experiences such as hallucinations or if the person poses a danger to themselves or others.<ref name="Devlin_2018">{{cite journal | vauthors = Devlin JW, Skrobik Y, Gélinas C, Needham DM, Slooter AJ, Pandharipande PP, Watson PL, Weinhouse GL, Nunnally ME, Rochwerg B, Balas MC, van den Boogaard M, Bosma KJ, Brummel NE, Chanques G, Denehy L, Drouot X, Fraser GL, Harris JE, Joffe AM, Kho ME, Kress JP, Lanphere JA, McKinley S, Neufeld KJ, Pisani MA, Payen JF, Pun BT, Puntillo KA, Riker RR, Robinson BR, Shehabi Y, Szumita PM, Winkelman C, Centofanti JE, Price C, Nikayin S, Misak CJ, Flood PD, Kiedrowski K, Alhazzani W | title = Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU | journal = Critical Care Medicine | volume = 46 | issue = 9 | pages = e825–e873 | date = September 2018 | pmid = 30113379 | doi = 10.1097/CCM.0000000000003299 }}</ref><ref name="Santos_2021">{{cite journal | vauthors = Santos CD, Rose MQ | title = Extrapyramidal Symptoms Induced by Treatment for Delirium: A Case Report | journal = Critical Care Nurse | volume = 41 | issue = 3 | pages = 50–54 | date = June 2021 | pmid = 34061189 | doi = 10.4037/ccn2021765 }}</ref><ref name="Siddiqi2016">{{cite journal | vauthors = Siddiqi N, Harrison JK, Clegg A, Teale EA, Young J, Taylor J, Simpkins SA | title = Interventions for preventing delirium in hospitalised non-ICU patients | journal = The Cochrane Database of Systematic Reviews | volume = 2016 | issue = 3 | pages = CD005563 | date = March 2016 | pmid = 26967259 | pmc = 10431752 | doi = 10.1002/14651858.CD005563.pub3 }}</ref><ref name="JAGS2016">{{cite journal | vauthors = Neufeld KJ, Yue J, Robinson TN, Inouye SK, Needham DM | title = Antipsychotic Medication for Prevention and Treatment of Delirium in Hospitalized Adults: A Systematic Review and Meta-Analysis | journal = Journal of the American Geriatrics Society | volume = 64 | issue = 4 | pages = 705–714 | date = April 2016 | pmid = 27004732 | pmc = 4840067 | doi = 10.1111/jgs.14076 }}</ref><ref name="Burry Cochrane">{{cite journal | vauthors = Burry L, Mehta S, Perreault MM, Luxenberg JS, Siddiqi N, Hutton B, Fergusson DA, Bell C, Rose L | title = Antipsychotics for treatment of delirium in hospitalised non-ICU patients | journal = The Cochrane Database of Systematic Reviews | volume = 2018 | issue = 6 | pages = CD005594 | date = June 2018 | pmid = 29920656 | pmc = 6513380 | doi = 10.1002/14651858.CD005594.pub3 | url = https://kclpure.kcl.ac.uk/portal/en/publications/antipsychotics-for-treatment-of-delirium-in-hospitalised-nonicu-patients(27bfcdeb-c56c-431e-930e-e29977f5f500).html | access-date = 2019-11-07 | url-status = live | archive-url = https://web.archive.org/web/20191107075053/https://kclpure.kcl.ac.uk/portal/en/publications/antipsychotics-for-treatment-of-delirium-in-hospitalised-nonicu-patients(27bfcdeb-c56c-431e-930e-e29977f5f500).html | archive-date = 2019-11-07 }}</ref> When delirium is caused by alcohol or [[sedative-hypnotic]] [[Drug withdrawal|withdrawal]], [[benzodiazepine]]s are typically used as a treatment.<ref name="Attard-2008">{{cite journal | vauthors = Attard A, Ranjith G, Taylor D | title = Delirium and its treatment | journal = CNS Drugs | volume = 22 | issue = 8 | pages = 631–644 | date = August 2008 | pmid = 18601302 | doi = 10.2165/00023210-200822080-00002 | s2cid = 94743 }}</ref> There is evidence that the risk of delirium in hospitalized people can be reduced by non-pharmacological care bundles (see {{section link|Delirium|Prevention}}).<ref name="Siddiqi2016" /> According to the text of [[DSM-5-TR]], although delirium affects only 1–2% of the overall population, 18–35% of adults presenting to the hospital will have delirium, and delirium will occur in 29–65% of people who are hospitalized.<ref name="DSM-5-TR" /> Delirium occurs in 11–51% of older adults after surgery, in 81% of those in the [[Intensive care unit|ICU]], and in 20–22% of individuals in nursing homes or post-acute care settings.<ref name="DSM-5-TR" /> Among those requiring critical care, delirium is a risk factor for death within the next year.<ref name=DSM-5-TR /><ref name="pmid15082703">{{cite journal | vauthors = Ely EW, Shintani A, Truman B, Speroff T, Gordon SM, Harrell FE, Inouye SK, Bernard GR, Dittus RS | title = Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit | journal = JAMA | volume = 291 | issue = 14 | pages = 1753–1762 | date = April 2004 | pmid = 15082703 | doi = 10.1001/jama.291.14.1753 | author-link = Eugene Wesley Ely | doi-access = free }}</ref>

Because of the confusion caused by similar signs and symptoms of delirium with other neuropsychiatric disorders like [[schizophrenia]] and [[psychosis]], treating delirium can be difficult, and might even cause death of the patient due to being treated with the wrong medications.<ref>{{cite journal | vauthors = Dharmarajan K, Swami S, Gou RY, Jones RN, Inouye SK | title = Pathway from Delirium to Death: Potential In-Hospital Mediators of Excess Mortality | journal = Journal of the American Geriatrics Society | volume = 65 | issue = 5 | pages = 1026–1033 | date = May 2017 | pmid = 28039852 | pmc = 5435507 | doi = 10.1111/jgs.14743 }}</ref><ref>{{cite journal | vauthors = Rockwood K, Cosway S, Carver D, Jarrett P, Stadnyk K, Fisk J | title = The risk of dementia and death after delirium | journal = Age and Ageing | volume = 28 | issue = 6 | pages = 551–556 | date = October 1999 | pmid = 10604507 | doi = 10.1093/ageing/28.6.551 }}</ref><ref>{{cite journal | vauthors = Leslie DL, Zhang Y, Holford TR, Bogardus ST, Leo-Summers LS, Inouye SK | title = Premature death associated with delirium at 1-year follow-up | journal = Archives of Internal Medicine | volume = 165 | issue = 14 | pages = 1657–1662 | date = July 2005 | pmid = 16043686 | doi = 10.1001/archinte.165.14.1657 }}</ref>

==Definition==
In common usage, delirium can refer to drowsiness, [[psychomotor agitation|agitation]], disorientation, or hallucinations. In [[medical terminology]], however, the core features of delirium include an acute disturbance in attention, awareness, and global cognition.

Although slight differences exist between the definitions of delirium in the [[Diagnostic and Statistical Manual of Mental Disorders|DSM-5-TR]]<ref name="DSM-5-TR" /> and [[ICD-10]],<ref>{{cite web |url=https://www.who.int/classifications/icd/en/bluebook.pdf |title= The ICD-10 Classification of Mental and Behavioural Disorders Clinical descriptions and diagnostic guidelines | vauthors =  Sartorius N, Henderson A, Strotzka H, Lipowski Z, Yu-cun S, You-xin X, Strömgren E, Glatzel J, Kühne GE, Misès R, Soldatos C, Pull C, Giel R, Jegede R, Malt U, Nadzharov R, Smulevitch A, Hagberg B, Perris C, Scharfetter C, Clare A, Cooper J, Corbett J, Griffith Edwards J, Gelder M, Goldberg D, Gossop M, Graham P, Kendell R, Marks I, Russell G, Rutter M, Shepherd M, West D, Wing J, Wing L, Neki J, Benson F, Cantwell D, Guze S, Helzer J, Holzman P, Kleinman A, Kupfer D, Mezzich J, Spitzer R, Lokar J |website=www.who.int [[World Health Organization]] |publisher=[[Microsoft Word]]  |agency=bluebook.doc |pages=56–7 |access-date=23 June 2021 |url-status=live|via=[[Microsoft Bing]]|archive-url=https://web.archive.org/web/20041017011412/http://www.who.int/classifications/icd/en/bluebook.pdf |archive-date=2004-10-17 }}</ref> the core features are broadly the same. In 2022, the American Psychiatric Association released the fifth edition text revision of the DSM ([[DSM-5-TR]]) with the following criteria for diagnosis:<ref name="DSM-5-TR" />
* A. Disturbance in attention and awareness. This is a required symptom and involves easy distraction, inability to maintain attentional focus, and varying levels of alertness.<ref name="American_Psychiatric_Publishing_2008">{{Cite book|title=The American Psychiatric Publishing textbook of psychiatry|date=2008| veditors = Hales RE, Yudofsky SC, Gabbard GO |publisher=American Psychiatric Publishing |isbn=9781585622573 |edition=5th |location=Washington, DC |oclc=145554590}}</ref>
* B. Onset is acute (from hours to days), representing a change from baseline mentation and often with fluctuations throughout the day
* C. At least one additional cognitive disturbance (in memory, [[Orientation (mental)|orientation]], language, visuospatial ability, or perception)
* D. The disturbances (criteria A and C) are not better explained by another neurocognitive disorder
* E. There is evidence that the disturbances above are a "direct physiological consequence" of another medical condition, substance intoxication or withdrawal, toxin, or various combinations of causes

==Signs and symptoms==
Delirium exists across a range of [[arousal]] levels, either as a state between normal wakefulness/alertness and coma (hypoactive) or as a state of heightened psychophysiological arousal (hyperactive). It can also alternate between the two (mixed level of activity). While requiring an acute disturbance in attention, awareness, and [[cognition]], the syndrome of delirium encompasses a broad range of additional neuropsychiatric disturbances.<ref name="American_Psychiatric_Publishing_2008" />

* '''Inattention''': A disturbance in [[attention]] is required for delirium diagnosis. This may present as an impaired ability to direct, focus, sustain, or shift [[attention]].<ref name="DSM-5-TR" />
* '''Memory impairment''': The [[memory impairment]] that occurs in delirium is often due to an inability to [[encoding (memory)|encode]] new information, largely as a result of having impaired [[attention]]. Older memories already in [[storage (memory)|storage]] are retained without need of concentration, so previously formed long-term memories (i.e., those formed before the onset of delirium) are usually preserved in all but the most severe cases of delirium, though [[recall (memory)|recall]] of such information may be impaired due to global impairment in cognition.
* '''Disorientation:''' A person may be disoriented to self, place, or time. Additionally, a person may be 'disoriented to situation' and not recognize their environment or appreciate what is going on around them.
* '''Disorganized thinking''': [[Thought disorder|Disorganized thinking]] is usually noticed with speech that makes limited sense with apparent irrelevancies, and can involve [[Alogia|poverty of speech]], [[Derailment (thought disorder)|loose associations]], [[perseveration]], [[Tangential speech|tangentiality]], and other signs of a formal thought disorder.
* '''Language disturbances''': [[Anomic aphasia]], [[paraphasia]], impaired comprehension, [[agraphia]], and word-finding difficulties all involve impairment of linguistic information processing.
* '''Sleep/wake disturbances''': Sleep disturbances in delirium reflect disruption in both sleep/wake and circadian rhythm regulation, typically characterized by fragmented sleep or even sleep-wake cycle reversal (i.e., active at night, sleeping during the day), including as an early sign preceding the onset of delirium.
* '''Psychotic and other erroneous beliefs''': Symptoms of [[psychosis]] include suspiciousness, overvalued ideation and frank delusions. [[Delusions]] are typically poorly formed and less [[Stereotypy|stereotyped]] than in schizophrenia or Alzheimer's disease. They usually relate to persecutory themes of impending danger or threat in the immediate environment (e.g., being poisoned by nurses).
* '''Perceptual disturbances''': These can include [[illusion]]s, which involve the misperception of real stimuli in the environment, or [[hallucination]]s, which involve the perception of stimuli that do not exist.
* '''Mood lability''': Distortions to perceived or communicated emotional states as well as [[Emotional lability|fluctuating emotional states]] can manifest in delirium (e.g., rapid changes between terror, sadness, joking, fear, anger, and frustration).<ref>{{cite journal | vauthors = Leentjens AF, Rundell J, Rummans T, Shim JJ, Oldham R, Peterson L, Philbrick K, Soellner W, Wolcott D, Freudenreich O | title = Delirium: An evidence-based medicine (EBM) monograph for psychosomatic medicine practice, commissioned by the Academy of Psychosomatic Medicine (APM) and the European Association of Consultation Liaison Psychiatry and Psychosomatics (EACLPP) | journal = Journal of Psychosomatic Research | volume = 73 | issue = 2 | pages = 149–152 | date = August 2012 | pmid = 22789420 | doi = 10.1016/j.jpsychores.2012.05.009 }}</ref>
* '''Motor activity changes:''' Delirium has been commonly classified into psychomotor subtypes of hypoactive, hyperactive, and mixed level of activity,<ref>{{cite journal | vauthors = Lipowski ZJ | title = Delirium in the elderly patient | journal = The New England Journal of Medicine | volume = 320 | issue = 9 | pages = 578–582 | date = March 1989 | pmid = 2644535 | doi = 10.1056/NEJM198903023200907 }}</ref> though studies are inconsistent as to their prevalence.<ref>{{cite journal | vauthors = de Rooij SE, Schuurmans MJ, van der Mast RC, Levi M | title = Clinical subtypes of delirium and their relevance for daily clinical practice: a systematic review | journal = International Journal of Geriatric Psychiatry | volume = 20 | issue = 7 | pages = 609–615 | date = July 2005 | pmid = 16021665 | doi = 10.1002/gps.1343 | s2cid = 37993802 }}</ref> Hypoactive cases are prone to non-detection or misdiagnosis as depression. A range of studies suggests that motor subtypes differ regarding underlying pathophysiology, treatment needs, functional prognosis, and risk of mortality, though inconsistent subtype definitions and poorer detection of hypoactive subtypes may influence the interpretation of these findings.<ref>{{cite journal | vauthors = Meagher D | title = Motor subtypes of delirium: past, present and future | journal = International Review of Psychiatry | volume = 21 | issue = 1 | pages = 59–73 | date = February 2009 | pmid = 19219713 | doi = 10.1080/09540260802675460 | s2cid = 11705848 }}</ref> The notion of unifying hypoactive and hyperactive states under the construct of delirium is commonly attributed to Lipowski.<ref name="Lipowski">{{Cite book|title=Delirium: Acute Brian Failure in Man|publisher=Charles C Thomas |isbn=0-398-03909-7 |location=Springfield, IL |year=1980}}</ref>
** '''Hyperactive''' symptoms include hyper-vigilance, restlessness, fast or loud speech, irritability, combativeness, impatience, swearing, singing, laughing, uncooperativeness, euphoria, anger, wandering, easy startling, fast motor responses, distractibility, tangentiality, nightmares, and persistent thoughts (hyperactive sub-typing is defined with at least three of the above).<ref name="Liptzin_1992">{{cite journal | vauthors = Liptzin B, Levkoff SE | title = An empirical study of delirium subtypes | journal = The British Journal of Psychiatry | volume = 161 | issue = 6 | pages = 843–845 | date = December 1992 | pmid = 1483173 | doi = 10.1192/bjp.161.6.843 | s2cid = 8754215 }}</ref>
** '''Hypoactive''' symptoms include decreased alertness, sparse or slow speech, lethargy, slowed movements, staring, and apathy.<ref name="Liptzin_1992" />
** '''Mixed level of activity''' describes instances of delirium where activity level is either normal or fluctuating between hyperactive and hypoactive.<ref name=DSM-5-TR />

==Causes==
Delirium arises through the interaction of a number of predisposing and precipitating factors.<ref>{{cite journal | vauthors = Magny E, Le Petitcorps H, Pociumban M, Bouksani-Kacher Z, Pautas É, Belmin J, Bastuji-Garin S, Lafuente-Lafuente C | title = Predisposing and precipitating factors for delirium in community-dwelling older adults admitted to hospital with this condition: A prospective case series | journal = PLOS ONE | volume = 13 | issue = 2 | pages = e0193034 | date = 2018-02-23 | pmid = 29474380 | pmc = 5825033 | doi = 10.1371/journal.pone.0193034 | doi-access = free | bibcode = 2018PLoSO..1393034M }}</ref><ref name=Ormseth>{{cite journal | vauthors = Ormseth CH, LaHue SC, Oldham MA, Josephson SA, Whitaker E, Douglas VC | title = Predisposing and Precipitating Factors Associated With Delirium: A Systematic Review | journal = JAMA Network Open | volume = 6 | issue = 1 | pages = e2249950 | date = January 2023 | pmid = 36607634 | pmc = 9856673 | doi = 10.1001/jamanetworkopen.2022.49950 }}</ref>

Individuals with multiple and/or significant predisposing factors are at high risk for an episode of delirium with a single and/or mild precipitating factor. Conversely, delirium may only result in low risk individuals if they experience a serious or multiple precipitating factors. These factors can change over time, thus an individual's risk of delirium is modifiable (see {{section link|Delirium|Prevention}}).

===Predisposing factors===
Important predisposing factors include the following:<ref name=Ormseth /><ref name="pmid19347026">{{cite journal | vauthors = Fong TG, Tulebaev SR, Inouye SK | title = Delirium in elderly adults: diagnosis, prevention and treatment | journal = Nature Reviews. Neurology | volume = 5 | issue = 4 | pages = 210–220 | date = April 2009 | pmid = 19347026 | pmc = 3065676 | doi = 10.1038/nrneurol.2009.24 }}</ref>
* 65 or more years of age
* Cognitive impairment/[[dementia]]
* Physical morbidity (e.g., [[Heart failure|biventricular failure]], [[cancer]], [[cerebrovascular disease]])
* Psychiatric morbidity (e.g., [[depression (mood)|depression]])
* Sensory impairment (i.e., vision and hearing)
* Functional dependence (e.g., requiring assistance for self-care or mobility)
* Dehydration/[[malnutrition]]
* Substance use disorder, especially [[Alcohol abuse|alcohol use disorder]] and anticholinergic abuse.

===Precipitating factors===
[[File:An alcoholic man with delirium Wellcome L0060780 (level correction).jpg|thumb|Acute confusional state caused by [[Alcohol withdrawal syndrome|alcohol withdrawal]], also known as [[delirium tremens]]]]
Any serious, acute biological factor that affects neurotransmitter, neuroendocrine, or neuroinflammatory pathways can precipitate an episode of delirium in a vulnerable brain.<ref>{{cite journal | vauthors = Hughes CG, Patel MB, Pandharipande PP | title = Pathophysiology of acute brain dysfunction: what's the cause of all this confusion? | journal = Current Opinion in Critical Care | volume = 18 | issue = 5 | pages = 518–526 | date = October 2012 | pmid = 22941208 | doi = 10.1097/MCC.0b013e328357effa | s2cid = 22572990 }}</ref> Certain elements of the clinical environment have also been associated with the risk of developing delirium.<ref>{{cite journal | vauthors = McCusker J, Cole M, Abrahamowicz M, Han L, Podoba JE, Ramman-Haddad L | title = Environmental risk factors for delirium in hospitalized older people | journal = Journal of the American Geriatrics Society | volume = 49 | issue = 10 | pages = 1327–1334 | date = October 2001 | pmid = 11890491 | doi = 10.1046/j.1532-5415.2001.49260.x | s2cid = 22910426 }}</ref> Some of the most common precipitating factors are listed below:<ref name=Ormseth /><ref name="Inouye2006" />
* Prolonged sleep restriction or deprivation
* Environmental, psychophysiological stress (as found in acute care settings)
** Inadequately controlled pain
** Immobilization, use of physical restraints<ref>{{cite journal | vauthors = Rollo E, Callea A, Brunetti V, Vollono C, Marotta J, Imperatori C, Frisullo G, Broccolini A, Della Marca G | title = Delirium in acute stroke: A prospective, cross-sectional, cohort study | journal = European Journal of Neurology | volume = 28 | issue = 5 | pages = 1590–1600 | date = May 2021 | pmid = 33476475 | doi = 10.1111/ene.14749 | s2cid = 231677499 }}</ref>
** Urinary retention, use of bladder catheter
** Emotional stress
** Severe constipation/fecal impaction
* Medications<ref name="CleggYoung">{{cite journal | vauthors = Clegg A, Young JB | title = Which medications to avoid in people at risk of delirium: a systematic review | journal = Age and Ageing | volume = 40 | issue = 1 | pages = 23–29 | date = January 2011 | pmid = 21068014 | doi = 10.1093/ageing/afq140 | doi-access = free }}</ref><ref>{{cite journal | vauthors = McCoy TH, Castro VM, Hart KL, Perlis RH | title = Stratified delirium risk using prescription medication data in a state-wide cohort | journal = General Hospital Psychiatry | volume = 71 | pages = 114–120 | date = July 2021 | pmid = 34091195 | pmc = 8249339 | doi = 10.1016/j.genhosppsych.2021.05.001 }}</ref>
** Sedatives ([[benzodiazepine]]s, [[opioid]]s), [[anticholinergics]], [[dopaminergic]]s, corticosteroids, [[polypharmacy]]
** General anesthetic
** Substance intoxication or withdrawal
* Primary neurologic conditions
** Severe drop in blood pressure, relative to the person's normal blood pressure ([[orthostatic hypotension]]) resulting in inadequate blood flow to the brain ([[cerebral hypoperfusion]])
** [[Stroke]]/[[transient ischemic attack]](TIA)
** [[Intracranial hemorrhage|Intracranial bleeding]]
** [[Meningitis]], [[encephalitis]]
* Concurrent illness
** Infections – especially respiratory (e.g. [[pneumonia]], [[COVID-19]]<ref>{{cite journal | vauthors = Saini A, Oh TH, Ghanem DA, Castro M, Butler M, Sin Fai Lam CC, Posporelis S, Lewis G, David AS, Rogers JP | title = Inflammatory and blood gas markers of COVID-19 delirium compared to non-COVID-19 delirium: a cross-sectional study | journal = Aging & Mental Health | volume = 26 | issue = 10 | pages = 2054–2061 | date = October 2022 | pmid = 34651536 | doi = 10.1080/13607863.2021.1989375 | s2cid = 238990849 | doi-access = free }}</ref>) and [[urinary tract infection]]s
** [[Iatrogenesis|Iatrogenic]] complications
** [[Hypoxia (medical)|Hypoxia]], [[Hypercapnia|hypercapnea]], [[anemia]]
** Poor nutritional status, dehydration, electrolyte imbalances, [[hypoglycemia]]
** [[Shock (circulatory)|Shock]], [[Myocardial infarction|heart attacks]], [[heart failure]]
** Metabolic derangements (e.g. [[SIADH]], [[Addison's disease]], [[hyperthyroidism]])
** Chronic/terminal illness (e.g. cancer)
** Post-traumatic event (e.g. fall, fracture)
** [[Mercury poisoning]] (e.g. [[erethism]])
* Major surgery (e.g. cardiac, orthopedic, vascular surgery)

==Pathophysiology==
The pathophysiology of delirium is still not well understood, despite extensive research.

===Animal models===
The lack of animal models that are relevant to delirium has left many key questions in delirium pathophysiology unanswered. Earliest rodent models of delirium used [[atropine]] (a [[muscarinic acetylcholine receptor]] blocker) to induce cognitive and electroencephalography (EEG) changes similar to delirium, and other [[anticholinergic]] drugs, such as [[biperiden]] and [[hyoscine]], have produced similar effects. Along with clinical studies using various drugs with anticholinergic activity, these models have contributed to a "cholinergic deficiency hypothesis" of delirium.<ref>{{cite journal | vauthors = Hshieh TT, Fong TG, Marcantonio ER, Inouye SK | title = Cholinergic deficiency hypothesis in delirium: a synthesis of current evidence | journal = The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences | volume = 63 | issue = 7 | pages = 764–772 | date = July 2008 | pmid = 18693233 | pmc = 2917793 | doi = 10.1093/gerona/63.7.764 }}</ref>

Profound systemic inflammation occurring during [[sepsis]] is also known to cause delirium (often termed sepsis-associated encephalopathy).<ref>{{cite journal | vauthors = Zampieri FG, Park M, Machado FS, Azevedo LC | title = Sepsis-associated encephalopathy: not just delirium | journal = Clinics | volume = 66 | issue = 10 | pages = 1825–1831 | date = 2011 | pmid = 22012058 | pmc = 3180153 | doi = 10.1590/S1807-59322011001000024 }}</ref> Animal models used to study the interactions between prior degenerative disease and overlying systemic inflammation have shown that even mild systemic inflammation causes acute and transient deficits in working memory among diseased animals.<ref name="Cunningham 2012">{{cite journal | vauthors = Cunningham C, Maclullich AM | title = At the extreme end of the psychoneuroimmunological spectrum: delirium as a maladaptive sickness behaviour response | journal = Brain, Behavior, and Immunity | volume = 28 | pages = 1–13 | date = February 2013 | pmid = 22884900 | pmc = 4157329 | doi = 10.1016/j.bbi.2012.07.012 }}</ref> Prior [[dementia]] or age-associated cognitive impairment is the primary predisposing factor for clinical delirium and "prior pathology" as defined by these new animal models may consist of synaptic loss, abnormal network connectivity, and "primed [[microglia]]" brain macrophages stimulated by prior neurodegenerative disease and aging to amplify subsequent inflammatory responses in the [[central nervous system]] (CNS).<ref name="Cunningham 2012" />

===Cerebrospinal fluid===
Studies of [[cerebrospinal fluid]] (CSF) in delirium are difficult to perform. Apart from the general difficulty of recruiting participants who are often unable to give consent, the inherently invasive nature of CSF sampling makes such research particularly challenging. However, a few studies have managed to sample CSF from persons undergoing spinal anesthesia for elective or emergency surgery.<ref name="Ormseth"/><ref>{{cite journal | vauthors = Derakhshan P, Imani F, Seyed-Siamdoust SA, Garousi S, Nouri N | title = Cerebrospinal Fluid and Spinal Anesthesia Parameters in Healthy Individuals versus Opium-addict Patients during Lower Limb Surgery | journal = Addiction & Health | volume = 12 | issue = 1 | pages = 11–17 | date = January 2020 | pmid = 32582410 | pmc = 7291896 | doi = 10.22122/ahj.v12i1.257 }}</ref><ref>{{cite journal | vauthors = Tigchelaar C, Atmosoerodjo SD, van Faassen M, Wardenaar KJ, De Deyn PP, Schoevers RA, Kema IP, Absalom AR | title = The Anaesthetic Biobank of Cerebrospinal fluid: a unique repository for neuroscientific biomarker research | journal = Annals of Translational Medicine | volume = 9 | issue = 6 | pages = 455 | date = March 2021 | pmid = 33850852 | pmc = 8039635 | doi = 10.21037/atm-20-4498 | doi-access = free }}</ref>

A 2018 [[systematic review]] showed that, broadly, delirium may be associated with neurotransmitter imbalance (namely [[serotonin]] and dopamine signaling), reversible fall in somatostatin, and increased cortisol.<ref name="Hall_2018">{{cite journal | vauthors = Hall RJ, Watne LO, Cunningham E, Zetterberg H, Shenkin SD, Wyller TB, MacLullich AM | title = CSF biomarkers in delirium: a systematic review | journal = International Journal of Geriatric Psychiatry | volume = 33 | issue = 11 | pages = 1479–1500 | date = November 2018 | pmid = 28585290 | doi = 10.1002/gps.4720 | url = http://discovery.ucl.ac.uk/10060989/ | access-date = 2019-07-01 | url-status = live | hdl-access = free | hdl = 20.500.11820/5933392d-bf79-4b57-940f-8a5c51f3b02e | s2cid = 205842730 | archive-url = https://web.archive.org/web/20210828054455/https://discovery.ucl.ac.uk/id/eprint/10060989/ | archive-date = 2021-08-28 }}</ref> The leading "neuroinflammatory hypothesis" (where neurodegenerative disease and aging leads the brain to respond to peripheral inflammation with an exaggerated CNS inflammatory response) has been described,<ref>{{cite journal | vauthors = Cerejeira J, Firmino H, Vaz-Serra A, Mukaetova-Ladinska EB | title = The neuroinflammatory hypothesis of delirium | journal = Acta Neuropathologica | volume = 119 | issue = 6 | pages = 737–754 | date = June 2010 | pmid = 20309566 | doi = 10.1007/s00401-010-0674-1 | hdl-access = free | s2cid = 206972133 | hdl = 10400.4/806 }}</ref> but current evidence is still conflicting and fails to concretely support this hypothesis.<ref name="Hall_2018" />

===Neuroimaging===
[[Neuroimaging]] provides an important avenue to explore the mechanisms that are responsible for delirium.<ref name="Nitchingham_2018">{{cite journal | vauthors = Nitchingham A, Kumar V, Shenkin S, Ferguson KJ, Caplan GA | title = A systematic review of neuroimaging in delirium: predictors, correlates and consequences | journal = International Journal of Geriatric Psychiatry | volume = 33 | issue = 11 | pages = 1458–1478 | date = November 2018 | pmid = 28574155 | doi = 10.1002/gps.4724 | s2cid = 20723293 }}</ref><ref name="Soiza_2008">{{cite journal | vauthors = Soiza RL, Sharma V, Ferguson K, Shenkin SD, Seymour DG, Maclullich AM | title = Neuroimaging studies of delirium: a systematic review | journal = Journal of Psychosomatic Research | volume = 65 | issue = 3 | pages = 239–248 | date = September 2008 | pmid = 18707946 | doi = 10.1016/j.jpsychores.2008.05.021 }}</ref> Despite progress in the development of [[magnetic resonance imaging]] (MRI), the large variety in imaging-based findings has limited our understanding of the changes in the brain that may be linked to delirium. Some challenges associated with imaging people diagnosed with delirium include participant recruitment and inadequate consideration of important confounding factors such as history of [[dementia]] and/or [[Depression (mood)|depression]], which are known to be associated with overlapping changes in the brain also observed on MRI.<ref name="Nitchingham_2018" />

Evidence for changes in structural and functional markers include: changes in [[White matter|white-matter]] integrity (white matter lesions), decreases in brain volume (likely as a result of tissue [[atrophy]]), abnormal [[Resting state fMRI|functional connectivity]] of brain regions responsible for normal processing of executive function, sensory processing, attention, emotional regulation, memory, and orientation, differences in autoregulation of the vascular vessels in the brain, reduction in cerebral blood flow and possible changes in brain metabolism (including cerebral tissue oxygenation and glucose hypometabolism).<ref name="Nitchingham_2018" /><ref name="Soiza_2008" /> Altogether, these changes in MRI-based measurements invite further investigation of the mechanisms that may underlie delirium, as a potential avenue to improve clinical management of people with this condition.<ref name="Nitchingham_2018" />

===Neurophysiology===
[[Electroencephalography]] (EEG) allows for continuous capture of global brain function and brain connectivity, and is useful in understanding real-time physiologic changes during delirium.<ref name="Shafi_2017">{{cite journal | vauthors = Shafi MM, Santarnecchi E, Fong TG, Jones RN, Marcantonio ER, Pascual-Leone A, Inouye SK | title = Advancing the Neurophysiological Understanding of Delirium | journal = Journal of the American Geriatrics Society | volume = 65 | issue = 6 | pages = 1114–1118 | date = June 2017 | pmid = 28165616 | pmc = 5576199 | doi = 10.1111/jgs.14748 }}</ref> Since the 1950s, delirium has been known to be associated with slowing of resting-state EEG rhythms, with abnormally decreased background alpha power and increased theta and delta frequency activity.<ref name="Shafi_2017" /><ref>{{cite journal | vauthors = Engel GL, Romano J | title = Delirium, a syndrome of cerebral insufficiency. 1959 | journal = The Journal of Neuropsychiatry and Clinical Neurosciences | volume = 16 | issue = 4 | pages = 526–538 | date = Fall 2004 | pmid = 15616182 | doi = 10.1176/appi.neuropsych.16.4.526 }}</ref>

From such evidence, a 2018 systematic review proposed a conceptual model that delirium results when insults/stressors trigger a breakdown of brain network dynamics in individuals with low brain resilience (i.e. people who already have underlying problems of low neural connectivity and/or low [[neuroplasticity]] like those with Alzheimer's disease).<ref name="Shafi_2017" />

===Neuropathology===
Only a handful of studies exist where there has been an attempt to correlate delirium with pathological findings at autopsy. One research study has been reported on 7 people who died during ICU admission.<ref>{{cite journal | vauthors = Janz DR, Abel TW, Jackson JC, Gunther ML, Heckers S, Ely EW | title = Brain autopsy findings in intensive care unit patients previously suffering from delirium: a pilot study | journal = Journal of Critical Care | volume = 25 | issue = 3 | pages = 538.e7–538.12 | date = September 2010 | pmid = 20580199 | pmc = 3755870 | doi = 10.1016/j.jcrc.2010.05.004 }}</ref> Each case was admitted with a range of primary pathologies, but all had [[acute respiratory distress syndrome]] and/or [[septic shock]] contributing to the delirium, 6 showed evidence of low brain perfusion and diffuse vascular injury, and 5 showed [[Hippocampus|hippocampal]] involvement. A case-control study showed that 9 delirium cases showed higher expression of [[HLA-DR]] and [[CD68]] (markers of microglial activation), IL-6 (cytokines pro-inflammatory and anti-inflammatory activities) and GFAP (marker of [[astrocyte]] activity) than age-matched controls; this supports a neuroinflammatory cause to delirium, but the conclusions are limited by methodological issues.<ref>{{cite journal | vauthors = Munster BC, Aronica E, Zwinderman AH, Eikelenboom P, Cunningham C, Rooij SE | title = Neuroinflammation in delirium: a postmortem case-control study | journal = Rejuvenation Research | volume = 14 | issue = 6 | pages = 615–622 | date = December 2011 | pmid = 21978081 | pmc = 4309948 | doi = 10.1089/rej.2011.1185 }}</ref>

A 2017 retrospective study correlating autopsy data with [[mini–mental state examination]] (MMSE) scores from 987 brain donors found that delirium combined with a pathological process of dementia accelerated MMSE score decline more than either individual process.<ref>{{cite journal | vauthors = Davis DH, Muniz-Terrera G, Keage HA, Stephan BC, Fleming J, Ince PG, Matthews FE, Cunningham C, Ely EW, MacLullich AM, Brayne C | title = Association of Delirium With Cognitive Decline in Late Life: A Neuropathologic Study of 3 Population-Based Cohort Studies | journal = JAMA Psychiatry | volume = 74 | issue = 3 | pages = 244–251 | date = March 2017 | pmid = 28114436 | pmc = 6037291 | doi = 10.1001/jamapsychiatry.2016.3423 }}</ref>

==Diagnosis==
The [[DSM-5-TR]] criteria are often the standard for diagnosing delirium clinically. However, early recognition of delirium's features using screening instruments, along with taking a careful history, can help in making a diagnosis of delirium. A diagnosis of delirium generally requires knowledge of a person's ''baseline'' level of [[cognitive function]]. This is especially important for treating people who have neurocognitive or neurodevelopmental disorders, whose baseline mental status may be mistaken as delirium.<ref>{{cite journal | vauthors = Morandi A, Grossi E, Lucchi E, Zambon A, Faraci B, Severgnini J, MacLullich A, Smith H, Pandharipande P, Rizzini A, Galeazzi M, Massariello F, Corradi S, Raccichini A, Scrimieri A, Morichi V, Gentile S, Lucchini F, Pecorella L, Mossello E, Cherubini A, Bellelli G | title = The 4-DSD: A New Tool to Assess Delirium Superimposed on Moderate to Severe Dementia | journal = Journal of the American Medical Directors Association | volume = 22 | issue = 7 | pages = 1535–1542.e3 | date = July 2021 | pmid = 33823162 | doi = 10.1016/j.jamda.2021.02.029 | s2cid = 233173770 }}</ref>

=== General settings ===
Guidelines recommend that delirium should be diagnosed consistently when present.<ref name = SIGN /><ref name = NICE>{{Cite web| title=Delirium: Prevention, diagnosis and management in hospital and long-term care| url=https://www.nice.org.uk/guidance/cg103| website=National Institute for Health and Care Excellence| date=28 July 2010| access-date=2023-01-31| archive-date=2023-06-09| archive-url=https://web.archive.org/web/20230609150014/https://www.nice.org.uk/guidance/CG103| url-status=live}}</ref> Much evidence reveals that in most centers delirium is greatly under-diagnosed.<ref>{{Cite journal | vauthors = Ibitoye T, So S, Shenkin SD, Anand A, Reed MJ, Vardy ER, Pendlebury ST, MacLullich AM |date=2023-05-15 |title=Delirium is under-reported in discharge summaries and in hospital administrative systems: a systematic review |url=https://deliriumjournal.com/article/74541-delirium-is-under-reported-in-discharge-summaries-and-in-hospital-administrative-systems-a-systematic-review |journal=Delirium |language=en |doi=10.56392/001c.74541|pmid=39654697 |pmc=7617113 }}</ref><ref>{{cite journal | vauthors = Bellelli G, Nobili A, Annoni G, Morandi A, Djade CD, Meagher DJ, Maclullich AM, Davis D, Mazzone A, Tettamanti M, Mannucci PM | title = Under-detection of delirium and impact of neurocognitive deficits on in-hospital mortality among acute geriatric and medical wards | journal = European Journal of Internal Medicine | volume = 26 | issue = 9 | pages = 696–704 | date = November 2015 | pmid = 26333532 | doi = 10.1016/j.ejim.2015.08.006 }}</ref><ref name="Sepulveda_2016">{{cite journal | vauthors = Sepulveda E, Franco JG, Trzepacz PT, Gaviria AM, Meagher DJ, Palma J, Viñuelas E, Grau I, Vilella E, de Pablo J | title = Delirium diagnosis defined by cluster analysis of symptoms versus diagnosis by DSM and ICD criteria: diagnostic accuracy study | journal = BMC Psychiatry | volume = 16 | issue = | pages = 167 | date = May 2016 | pmid = 27229307 | pmc = 4882791 | doi = 10.1186/s12888-016-0878-6 | doi-access = free }}</ref><ref>{{cite journal | vauthors = McCoy TH, Snapper L, Stern TA, Perlis RH | title = Underreporting of Delirium in Statewide Claims Data: Implications for Clinical Care and Predictive Modeling | journal = Psychosomatics | volume = 57 | issue = 5 | pages = 480–488 | year = 2016 | pmid = 27480944 | doi = 10.1016/j.psym.2016.06.001 | s2cid = 3300073 }}</ref> A systematic review of large scale routine data studies reporting data on delirium detection tools showed important variations in tool completion rates and tool positive score rates. Some tools, even if completed at high rates, showed delirium positive score rates that there much lower than the expected delirium occurrence level, suggesting low sensitivity in practice.<ref>{{cite journal | vauthors = Penfold RS, Squires C, Angus A, Shenkin SD, Ibitoye T, Tieges Z, Neufeld KJ, Avelino-Silva TJ, Davis D, Anand A, Duckworth AD, Guthrie B, MacLullich AM | title = Delirium detection tools show varying completion rates and positive score rates when used at scale in routine practice in general hospital settings: A systematic review | journal = Journal of the American Geriatrics Society | volume = 72 | issue = 5 | pages = 1508–1524 | date = May 2024 | pmid = 38241503 | doi = 10.1111/jgs.18751 | doi-access = free }}</ref>

There is evidence that delirium detection and coding rates can show improvements in response to guidelines and education; for example, whole country data in England and Scotland (sample size 7.7M people per year) show that there were large increases (3-4 fold) in delirium coding between 2012 and 2020.<ref>{{cite journal | vauthors = Ibitoye T, Jackson TA, Davis D, MacLullich AM | title = Trends in delirium coding rates in older hospital inpatients in England and Scotland: full population data comprising 7.7M patients per year show substantial increases between 2012 and 2020 | journal = Delirium Communications | volume = 2023 | pages = 84051 | date = July 2023 | pmid = 37654785 | pmc = 7614999 | doi = 10.56392/001c.84051 }}</ref> Delirium detection in general acute care settings can be assisted by the use of validated delirium screening tools. Many such tools have been published, and they differ in a variety of characteristics (e.g., duration, complexity, and need for training). It is also important to ensure that a given tool has been validated for the setting where it is being used.

Examples of tools in use in clinical practice include:
* [[Confusion Assessment Method]] (CAM),<ref>{{cite journal | vauthors = Inouye SK, van Dyck CH, Alessi CA, Balkin S, Siegal AP, Horwitz RI | title = Clarifying confusion: the confusion assessment method. A new method for detection of delirium | journal = Annals of Internal Medicine | volume = 113 | issue = 12 | pages = 941–948 | date = December 1990 | pmid = 2240918 | doi = 10.7326/0003-4819-113-12-941 | s2cid = 7740657 }}</ref> including variants such as the 3-Minute Diagnostic Interview for the CAM (3D-CAM)<ref>{{cite journal | vauthors = Marcantonio ER, Ngo LH, O'Connor M, Jones RN, Crane PK, Metzger ED, Inouye SK | title = 3D-CAM: derivation and validation of a 3-minute diagnostic interview for CAM-defined delirium: a cross-sectional diagnostic test study | journal = Annals of Internal Medicine | volume = 161 | issue = 8 | pages = 554–561 | date = October 2014 | pmid = 25329203 | pmc = 4319978 | doi = 10.7326/M14-0865 }}</ref> and brief CAM (bCAM)<ref>{{cite journal | vauthors = Han JH, Wilson A, Vasilevskis EE, Shintani A, Schnelle JF, Dittus RS, Graves AJ, Storrow AB, Shuster J, Ely EW | title = Diagnosing delirium in older emergency department patients: validity and reliability of the delirium triage screen and the brief confusion assessment method | journal = Annals of Emergency Medicine | volume = 62 | issue = 5 | pages = 457–465 | date = November 2013 | pmid = 23916018 | pmc = 3936572 | doi = 10.1016/j.annemergmed.2013.05.003 }}</ref>
* Delirium Observation Screening Scale (DOS)<ref>{{cite journal | vauthors = Schuurmans MJ, Shortridge-Baggett LM, Duursma SA | title = The Delirium Observation Screening Scale: a screening instrument for delirium | journal = Research and Theory for Nursing Practice | volume = 17 | issue = 1 | pages = 31–50 | date = 2003-01-01 | pmid = 12751884 | doi = 10.1891/rtnp.17.1.31.53169 | s2cid = 219203272 }}</ref>
* Nursing Delirium Screening Scale (Nu-DESC)<ref>{{cite journal | vauthors = Gaudreau JD, Gagnon P, Harel F, Tremblay A, Roy MA | title = Fast, systematic, and continuous delirium assessment in hospitalized patients: the nursing delirium screening scale | journal = Journal of Pain and Symptom Management | volume = 29 | issue = 4 | pages = 368–375 | date = April 2005 | pmid = 15857740 | doi = 10.1016/j.jpainsymman.2004.07.009 | doi-access = free }}</ref>
* Recognizing Acute Delirium As part of your Routine (RADAR)<ref>{{cite journal | vauthors = Voyer P, Champoux N, Desrosiers J, Landreville P, McCusker J, Monette J, Savoie M, Richard S, Carmichael PH | title = Recognizing acute delirium as part of your routine [RADAR]: a validation study | journal = BMC Nursing | volume = 14 | pages = 19 | date = 2015-01-01 | pmid = 25844067 | pmc = 4384313 | doi = 10.1186/s12912-015-0070-1 | doi-access = free }}</ref>
* [[4AT]] (4 A's Test)<ref name="Tieges_2021">{{cite journal | vauthors = Tieges Z, Maclullich AM, Anand A, Brookes C, Cassarino M, O'connor M, Ryan D, Saller T, Arora RC, Chang Y, Agarwal K, Taffet G, Quinn T, Shenkin SD, Galvin R | title = Diagnostic accuracy of the 4AT for delirium detection in older adults: systematic review and meta-analysis | journal = Age and Ageing | volume = 50 | issue = 3 | pages = 733–743 | date = May 2021 | pmid = 33951145 | pmc = 8099016 | doi = 10.1093/ageing/afaa224 }}</ref>
* Delirium Diagnostic Tool-Provisional (DDT-Pro),<ref>{{cite journal | vauthors = Kean J, Trzepacz PT, Murray LL, Abell M, Trexler L | title = Initial validation of a brief provisional diagnostic scale for delirium | journal = Brain Injury | volume = 24 | issue = 10 | pages = 1222–1230 | date = 2010 | pmid = 20645705 | doi = 10.3109/02699052.2010.498008 | s2cid = 27856235 }}</ref><ref>{{cite journal | vauthors = Franco JG, Ocampo MV, Velásquez-Tirado JD, Zaraza DR, Giraldo AM, Serna PA, López C, Zuluaga A, Sepúlveda E, Kean J, Trzepacz PT | title = Validation of the Delirium Diagnostic Tool-Provisional (DDT-Pro) With Medical Inpatients and Comparison With the Confusion Assessment Method Algorithm | journal = The Journal of Neuropsychiatry and Clinical Neurosciences | volume = 32 | issue = 3 | pages = 213–226 | date = 2020 | pmid = 31662094 | doi = 10.1176/appi.neuropsych.18110255 | doi-access = free }}</ref> also for subsyndromal delirium<ref>{{cite journal | vauthors = Franco JG, Trzepacz PT, Sepúlveda E, Ocampo MV, Velásquez-Tirado JD, Zaraza DR, Restrepo C, Giraldo AM, Serna PA, Zuluaga A, López C | title = Delirium diagnostic tool-provisional (DDT-Pro) scores in delirium, subsyndromal delirium and no delirium | journal = General Hospital Psychiatry | volume = 67 | pages = 107–114 | date = 2020 | pmid = 33091783 | doi = 10.1016/j.genhosppsych.2020.10.003 | s2cid = 225053525 }}</ref>

===Intensive care unit===
People who are in the ICU are at greater risk of delirium, and ICU delirium may lead to prolonged ventilation, longer stays in the hospital, increased stress on family and caregivers, and an increased chance of death.<ref name="Burry_2019">{{cite journal | vauthors = Burry L, Hutton B, Williamson DR, Mehta S, Adhikari NK, Cheng W, Ely EW, Egerod I, Fergusson DA, Rose L | title = Pharmacological interventions for the treatment of delirium in critically ill adults | journal = The Cochrane Database of Systematic Reviews | volume = 2019 | issue = 9 | pages = CD011749 | date = September 2019 | pmid = 31479532 | pmc = 6719921 | doi = 10.1002/14651858.CD011749.pub2 }}</ref> In the ICU, international guidelines recommend that every person admitted gets checked for delirium every day (usually twice or more a day) using a validated clinical tool.<ref name="pmid11902253">{{cite journal | vauthors = Jacobi J, Fraser GL, Coursin DB, Riker RR, Fontaine D, Wittbrodt ET, Chalfin DB, Masica MF, Bjerke HS, Coplin WM, Crippen DW, Fuchs BD, Kelleher RM, Marik PE, Nasraway SA, Murray MJ, Peruzzi WT, Lumb PD | title = Clinical practice guidelines for the sustained use of sedatives and analgesics in the critically ill adult | journal = Critical Care Medicine | volume = 30 | issue = 1 | pages = 119–141 | date = January 2002 | pmid = 11902253 | doi = 10.1097/00003246-200201000-00020 | s2cid = 16654002 }}</ref> Key elements of detecting delirium in the ICU are whether a person can pay attention during a listening task and follow simple commands.<ref name="www.icudelirium.org">{{cite web|url=https://www.icudelirium.org/medical-professionals/delirium/monitoring-delirium-in-the-icu|title=Critical Illness, Brain Dysfunction, and Survivorshpi (CIBS) Center|website=www.icudelirium.org|access-date=2019-03-22|archive-date=2019-03-22|archive-url=https://web.archive.org/web/20190322044929/https://www.icudelirium.org/medical-professionals/delirium/monitoring-delirium-in-the-icu|url-status=live}}</ref> The two most widely used are the Confusion Assessment Method for the ICU (CAM-ICU)<ref name="Ely2001">{{cite journal | vauthors = Ely EW, Inouye SK, Bernard GR, Gordon S, Francis J, May L, Truman B, Speroff T, Gautam S, Margolin R, Hart RP, Dittus R | title = Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU) | journal = JAMA | volume = 286 | issue = 21 | pages = 2703–2710 | date = December 2001 | pmid = 11730446 | doi = 10.1001/jama.286.21.2703 | hdl-access = free | doi-access = free | hdl = 10818/12438 }}</ref> and the Intensive Care Delirium Screening Checklist (ICDSC).<ref name="Bergeron2001">{{cite journal | vauthors = Bergeron N, Dubois MJ, Dumont M, Dial S, Skrobik Y | title = Intensive Care Delirium Screening Checklist: evaluation of a new screening tool | journal = Intensive Care Medicine | volume = 27 | issue = 5 | pages = 859–864 | date = May 2001 | pmid = 11430542 | doi = 10.1007/s001340100909 | s2cid = 24997942 }}</ref> Translations of these tools exist in over 20 languages and are used ICUs globally with instructional videos and implementation tips available.<ref name="www.icudelirium.org" /> For children in need of intensive care there are validated clinical tools adjusted according to age. The recommended tools are preschool and pediatric Confusion Assessment Methods for the ICU (ps/pCAM-ICU) or the Cornell Assessment for Pediatric Delirium (CAPD) as the most valid and reliable delirium monitoring tools in critically ill children or adolescents.<ref>{{cite journal | vauthors = Smith HA, Besunder JB, Betters KA, Johnson PN, Srinivasan V, Stormorken A, Farrington E, Golianu B, Godshall AJ, Acinelli L, Almgren C, Bailey CH, Boyd JM, Cisco MJ, Damian M, deAlmeida ML, Fehr J, Fenton KE, Gilliland F, Grant MJ, Howell J, Ruggles CA, Simone S, Su F, Sullivan JE, Tegtmeyer K, Traube C, Williams S, Berkenbosch JW | title = 2022 Society of Critical Care Medicine Clinical Practice Guidelines on Prevention and Management of Pain, Agitation, Neuromuscular Blockade, and Delirium in Critically Ill Pediatric Patients With Consideration of the ICU Environment and Early Mobility | journal = Pediatric Critical Care Medicine | volume = 23 | issue = 2 | pages = e74–e110 | date = February 2022 | pmid = 35119438 | doi = 10.1097/PCC.0000000000002873 | s2cid = 246530757 | doi-access = free }}</ref>

More emphasis is placed on regular screening over the choice of tool used. This, coupled with proper documentation and informed awareness by the healthcare team, can affect clinical outcomes.<ref name="www.icudelirium.org" /> Without using one of these tools, 75% of ICU delirium can be missed by the healthcare team, leaving the person without any likely interventions to help reduce the duration of delirium.<ref name="www.icudelirium.org" /><ref>{{cite journal | vauthors = Jones SF, Pisani MA | title = ICU delirium: an update | journal = Current Opinion in Critical Care | volume = 18 | issue = 2 | pages = 146–151 | date = April 2012 | pmid = 22322260 | doi = 10.1097/MCC.0b013e32835132b9 | s2cid = 404583 }}</ref>

===Differential diagnosis===
There are conditions that might have similar clinical presentations to those seen in delirium. These include dementia,<ref>{{Cite web | vauthors = Wong N, Abraham G |url=https://www.ebmedicine.net/topics/psychiatric-behavioral/delirium-agitation|title=Treating Delirium & Agitation in the Emergency Room, 2015 | work = EB Medicine |access-date=2019-11-25|archive-date=2019-12-23|archive-url=https://web.archive.org/web/20191223105314/https://www.ebmedicine.net/topics/psychiatric-behavioral/delirium-agitation|url-status=live}}</ref><ref name="Soiza_2019" /><ref name="Oh_2017" /><ref name = "Sugalski_2019" /><ref name="Grover_2018">{{cite journal | vauthors = Grover S, Avasthi A | title = Clinical Practice Guidelines for Management of Delirium in Elderly | journal = Indian Journal of Psychiatry | volume = 60 | issue = Suppl 3 | pages = S329–S340 | date = February 2018 | pmid = 29535468 | pmc = 5840908 | doi = 10.4103/0019-5545.224473 | doi-access = free }}</ref> depression,<ref name="Grover_2018" /><ref name="Oh_2017" /> psychosis,<ref name=pseudodelirium /><ref name="Grover_2018" /><ref name="Oh_2017" /> [[catatonia]],<ref name=pseudodelirium /> and other conditions that affect cognitive function.<ref name = "Sugalski_2019">{{cite journal | vauthors = Sugalski G, Ullo M, Winograd SM | title = Making Sense of Delirium in the Emergency Department. | journal = Emergency Medicine Reports | date = February 2019 | volume = 40 | issue = 3 | id = {{ProQuest|2175238208}} }}</ref>
* '''Dementia''': This group of disorders is acquired (non-congenital) with usually irreversible cognitive and psychosocial functional decline. [[Dementia]] usually results from an identifiable degenerative brain disease (e.g., [[Alzheimer disease]] or [[Huntington's disease]]), requires chronic impairment (versus acute onset in delirium), and is typically not associated with changes in level of consciousness.<ref>{{Cite book | vauthors = Mendez MF, Cummings JL |url=https://books.google.com/books?id=LzM4v_OruZ8C&pg=PR11 |title=Dementia: A Clinical Approach |date=2003 |publisher=Butterworth-Heinemann |isbn=978-0-7506-7470-6 |language=en |access-date=2022-05-17 |archive-date=2023-12-30 |archive-url=https://web.archive.org/web/20231230124122/https://books.google.com/books?id=LzM4v_OruZ8C&pg=PR11#v=onepage&q&f=false |url-status=live }}</ref> Dementia is different from delirium in that dementia lasts long-term while delirium lasts short-term.
* '''Depression''': Similar symptoms exist between [[clinical depression|depression]] and delirium (especially the hypoactive subtype). Gathering a history from other caregivers can clarify baseline mentation.<ref>{{cite journal | vauthors = O'Sullivan R, Inouye SK, Meagher D | title = Delirium and depression: inter-relationship and clinical overlap in elderly people | journal = The Lancet. Psychiatry | volume = 1 | issue = 4 | pages = 303–311 | date = September 2014 | pmid = 26360863 | pmc = 5338740 | doi = 10.1016/S2215-0366(14)70281-0 }}</ref>
* '''Psychosis''': In general, people with ''primary'' psychosis have intact cognitive function; however, primary psychosis can mimic delirium when it presents with disorganized thoughts and mood dysregulation. This is particularly true in the condition known as delirious mania.<ref name=pseudodelirium />
* '''Other mental illnesses''': Some mental illnesses, such as a manic episode of bipolar disorder, [[Depersonalization-derealization disorder|depersonalization disorder]], or other dissociative conditions, can present with features similar to that of delirium.<ref name=pseudodelirium /> Such condition, however, would not qualify for a diagnosis of delirium per DSM-5-TR criterion D (i.e., fluctuating cognitive symptoms occurring as part of a ''primary'' ''mental'' disorder are results of the said mental disorder itself), while ''physical'' disorders (e.g., infections, hypoxia, etc.) can precipitate delirium as a mental side-effect/symptom.<ref name=DSM-5-TR />

==Prevention==
Treating delirium that is already established is challenging and for this reason, preventing delirium before it begins is ideal. Prevention approaches include screening to identify people who are at risk, and medication-based and non-medication based (non-pharmacological) treatments.<ref name="Burton_2021">{{cite journal | vauthors = Burton JK, Craig L, Yong SQ, Siddiqi N, Teale EA, Woodhouse R, Barugh AJ, Shepherd AM, Brunton A, Freeman SC, Sutton AJ, Quinn TJ | title = Non-pharmacological interventions for preventing delirium in hospitalised non-ICU patients | journal = The Cochrane Database of Systematic Reviews | volume = 2021 | issue = 11 | pages = CD013307 | date = November 2021 | pmid = 34826144 | pmc = 8623130 | doi = 10.1002/14651858.CD013307.pub3 }}</ref>

An estimated 30–40% of all cases of delirium could be prevented in cognitively at-risk populations, and high rates of delirium reflect negatively on the quality of care.<ref name="Inouye2006" /> Episodes of delirium can be prevented by identifying hospitalized people at risk of the condition. This includes individuals over age 65, with a cognitive impairment, undergoing major surgery, or with severe illness.<ref name="NICE" /> Routine delirium screening is recommended in such populations. It is thought that a personalized approach to prevention that includes different approaches together can decrease rates of delirium by 27% among the elderly.<ref>{{cite journal | vauthors = Martinez F, Tobar C, Hill N | title = Preventing delirium: should non-pharmacological, multicomponent interventions be used? A systematic review and meta-analysis of the literature | journal = Age and Ageing | volume = 44 | issue = 2 | pages = 196–204 | date = March 2015 | pmid = 25424450 | doi = 10.1093/ageing/afu173 | doi-access = free }}</ref><ref name="Siddiqi2016" />

In 1999, [[Sharon K. Inouye]] at Yale University, founded the Hospital Elder Life Program (HELP)<ref>{{cite journal | vauthors = Hshieh TT, Yang T, Gartaganis SL, Yue J, Inouye SK | title = Hospital Elder Life Program: Systematic Review and Meta-analysis of Effectiveness | journal = The American Journal of Geriatric Psychiatry | volume = 26 | issue = 10 | pages = 1015–1033 | date = October 2018 | pmid = 30076080 | pmc = 6362826 | doi = 10.1016/j.jagp.2018.06.007 }}</ref> which has since become recognized as a proven model for preventing delirium.<ref name="ReferenceA">{{cite journal | vauthors = Waite LJ | title = The Demographic Faces of the Elderly | journal = Population and Development Review | volume = 30 | issue = Supplement | pages = 3–16 | date = 2004 | pmid = 19129925 | pmc = 2614322 }}</ref> HELP prevents delirium among the elderly through active participation and engagement with these individuals. There are two working parts to this program, medical professionals such as a trained nurse, and volunteers, who are overseen by the nurse. The volunteer program equips each trainee with the adequate basic geriatric knowledge and interpersonal skills to interact with patients. Volunteers perform the range of motion exercises, cognitive stimulation, and general conversation<ref>{{cite journal | vauthors = Zachary W, Kirupananthan A, Cotter S, Barbara GH, Cooke RC, Sipho M | title = The impact of Hospital Elder Life Program interventions, on 30-day readmission Rates of older hospitalized patients | journal = Archives of Gerontology and Geriatrics | volume = 86 | pages = 103963 | date = 2020 | pmid = 31733512 | doi = 10.1016/j.archger.2019.103963 | s2cid = 208086667 }}</ref> with elderly patients who are staying in the hospital. Alternative effective delirium prevention programs have been developed, some of which do not require volunteers.<ref>{{cite journal | vauthors = Ludolph P, Stoffers-Winterling J, Kunzler AM, Rösch R, Geschke K, Vahl CF, Lieb K | title = Non-Pharmacologic Multicomponent Interventions Preventing Delirium in Hospitalized People | journal = Journal of the American Geriatrics Society | volume = 68 | issue = 8 | pages = 1864–1871 | date = August 2020 | pmid = 32531089 | doi = 10.1111/jgs.16565 | doi-access = free }}</ref>

Prevention efforts often fall on caregivers. Caregivers often have a lot expected of them and this is where socioeconomic status plays a role in prevention.<ref>{{cite journal | vauthors = Tough H, Brinkhof MW, Siegrist J, Fekete C | title = Social inequalities in the burden of care: a dyadic analysis in the caregiving partners of persons with a physical disability | journal = International Journal for Equity in Health | volume = 19 | issue = 1 | pages = 3 | date = December 2019 | pmid = 31892324 | pmc = 6938621 | doi = 10.1186/s12939-019-1112-1 | author5 = for the SwiSCI Study Group | doi-access = free }}</ref> If prevention requires constant mental stimulation and daily exercise, this takes time out of the caregiver's day. Based on socioeconomic classes, this may be valuable time that would be used working to support the family. This leads to a disproportionate number of individuals who experience delirium being from marginalized identities.<ref name="ReferenceA"/> Programs such as the Hospital Elder Life Program can attempt to combat these societal issues by providing additional support and education about delirium that may not otherwise be accessible.

=== Non-pharmacological ===
Delirium may be prevented and treated by using non-pharmacologic approaches focused on risk factors, such as constipation, dehydration, low oxygen levels, immobility, visual or hearing impairment, sleep disturbance, functional decline, and by removing or minimizing problematic medications.<ref name=NICE/><ref name="Oh_2017">{{cite journal | vauthors = Oh ES, Fong TG, Hshieh TT, Inouye SK | title = Delirium in Older Persons: Advances in Diagnosis and Treatment | journal = JAMA | volume = 318 | issue = 12 | pages = 1161–1174 | date = September 2017 | pmid = 28973626 | pmc = 5717753 | doi = 10.1001/jama.2017.12067 }}</ref> Ensuring a therapeutic environment (e.g., individualized care, clear communication, adequate reorientation and lighting during daytime, promoting uninterrupted [[sleep hygiene]] with minimal noise and light at night, minimizing room relocation, having familiar objects like family pictures, providing earplugs, and providing adequate nutrition, pain control, and assistance toward early mobilization) may also aid in preventing delirium.<ref name="Siddiqi2016" /><ref name=Inouye2006>{{cite journal | vauthors = Inouye SK | title = Delirium in older persons | journal = The New England Journal of Medicine | volume = 354 | issue = 11 | pages = 1157–1165 | date = March 2006 | pmid = 16540616 | doi = 10.1056/NEJMra052321 | url = http://nrs.harvard.edu/urn-3:HUL.InstRepos:13956255 | access-date = 2019-01-04 | url-status = live | s2cid = 245337 | archive-url = https://web.archive.org/web/20210828054457/https://dash.harvard.edu/handle/1/13956255 | archive-date = 2021-08-28 }}</ref><ref>{{cite journal | vauthors = Poongkunran C, John SG, Kannan AS, Shetty S, Bime C, Parthasarathy S | title = A meta-analysis of sleep-promoting interventions during critical illness | journal = The American Journal of Medicine | volume = 128 | issue = 10 | pages = 1126–1137.e1 | date = October 2015 | pmid = 26071825 | pmc = 4577445 | doi = 10.1016/j.amjmed.2015.05.026 }}</ref><ref>{{cite journal | vauthors = Flannery AH, Oyler DR, Weinhouse GL | title = The Impact of Interventions to Improve Sleep on Delirium in the ICU: A Systematic Review and Research Framework | journal = Critical Care Medicine | volume = 44 | issue = 12 | pages = 2231–2240 | date = December 2016 | pmid = 27509391 | doi = 10.1097/CCM.0000000000001952 | s2cid = 24494855 }}</ref> Research into pharmacologic prevention and treatment is weak and insufficient to make proper recommendations.<ref name="Oh_2017" />

=== Pharmacological ===
Melatonin and other pharmacological agents have been studied for delirium prevention, but evidence is conflicting.<ref name=Siddiqi2016 /><ref>{{cite journal | vauthors = Gosch M, Nicholas JA | title = Pharmacologic prevention of postoperative delirium | journal = Zeitschrift für Gerontologie und Geriatrie | volume = 47 | issue = 2 | pages = 105–109 | date = February 2014 | pmid = 24619041 | doi = 10.1007/s00391-013-0598-1 | s2cid = 19868320 }}</ref> Avoidance or cautious use of benzodiazepines has been recommended for reducing the risk of delirium in critically ill individuals.<ref name="pmid28190430">{{cite book |vauthors=Slooter AJ, Van De Leur RR, Zaal IJ |title=Critical Care Neurology Part II |chapter=Delirium in critically ill patients |volume=141 |pages=449–466 |year=2017 |pmid=28190430 |doi=10.1016/B978-0-444-63599-0.00025-9 |series=Handbook of Clinical Neurology |isbn=9780444635990 }}</ref> It is unclear if the medication [[donepezil]], a [[Cholinesterase inhibitors|cholinesterase inhibitor]], reduces delirium following surgery.<ref name="Siddiqi2016" /> There is also no clear evidence to suggest that [[citicoline]], [[methylprednisolone]], or [[antipsychotic]] medications prevent delirium.<ref name="Siddiqi2016" /> A review of intravenous versus inhalational maintenance of anaesthesia for postoperative cognitive outcomes in elderly people undergoing non-cardiac surgery showed little or no difference in postoperative delirium according to the type of anaesthetic maintenance agents<ref>{{cite journal | vauthors = Miller D, Lewis SR, Pritchard MW, Schofield-Robinson OJ, Shelton CL, Alderson P, Smith AF | title = Intravenous versus inhalational maintenance of anaesthesia for postoperative cognitive outcomes in elderly people undergoing non-cardiac surgery | journal = The Cochrane Database of Systematic Reviews | volume = 8 | issue = 8 | pages = CD012317 | date = August 2018 | pmid = 30129968 | pmc = 6513211 | doi = 10.1002/14651858.CD012317.pub2 }}</ref> in five studies (321 participants). The authors of this review were uncertain whether maintenance of anaesthesia with [[propofol]]-based total intravenous anaesthesia (TIVA) or with inhalational agents can affect the incidence rate of postoperative delirium.

'''Interventions for preventing delirium in long-term care or hospital'''

The current evidence suggests that software-based interventions to identify medications that could contribute to delirium risk and recommend a pharmacist's medication review probably reduces incidence of delirium in older adults in long-term care.<ref name="Woodhouse_2019">{{cite journal | vauthors = Woodhouse R, Burton JK, Rana N, Pang YL, Lister JE, Siddiqi N | title = Interventions for preventing delirium in older people in institutional long-term care | journal = The Cochrane Database of Systematic Reviews | volume = 4 | issue = 4 | pages = CD009537 | date = April 2019 | pmid = 31012953 | pmc = 6478111 | doi = 10.1002/14651858.cd009537.pub3 }}</ref> The benefits of hydration reminders and education on risk factors and care homes' solutions for reducing delirium is still uncertain.<ref name="Woodhouse_2019" />

For inpatients in a hospital setting, numerous approaches have been suggested to prevent episodes of delirium including targeting risk factors such as sleep deprivation, mobility problems, dehydration, and impairments to a person's sensory system. Often a 'multicomponent' approach by an interdisciplinary team of health care professionals is suggested for people in the hospital at risk of delirium, and there is some evidence that this may decrease to incidence of delirium by up to 43% and may reduce the length of time that the person is hospitalized.<ref name="Burton_2021" />

==Treatment==
Most often, delirium is reversible; however, people with delirium require treatment for the underlying cause(s), often to prevent injury and other poor outcomes directly related to delirium.<ref name="Burry_2019" />

Treatment of delirium requires attention to multiple domains including the following:<ref name="Delirium" /><ref name="Inouye2006" />
* Identify and treat the underlying medical disorder or cause(s)
* Addressing any other possible predisposing and precipitating factors that might be disrupting brain function
* Optimize physiology and conditions for brain recovery (e.g., oxygenation, hydration, nutrition, electrolytes, metabolites, medication review)
* Detect and manage distress and behavioral disturbances (e.g., pain control)
* Maintaining mobility
* Provide rehabilitation through cognitive engagement and mobilization
* Communicate effectively with the person experiencing delirium and their carers or caregivers
* Provide adequate follow-up including consideration of possible dementia and post-traumatic stress.<ref name="Delirium"/>

===Multidomain interventions===

These interventions are the first steps in managing acute delirium, and there are many overlaps with delirium preventative strategies.<ref name="Scottish_Intercollegiate_Guidelines_Network_2019" /> In addition to treating immediate life-threatening causes of delirium (e.g., low O{{sub|2}}, low blood pressure, low glucose, dehydration), interventions include optimizing the hospital environment by reducing ambient noise, providing proper lighting, offering pain relief, promoting healthy sleep-wake cycles, and minimizing room changes.<ref name="Scottish_Intercollegiate_Guidelines_Network_2019">{{Cite book|title=Risk reduction and management of delirium: a national clinical guideline |isbn=978-1-909103-68-9 |location=Edinburgh | publisher = Scottish Intercollegiate Guidelines Network |oclc=1099827664|year = 2019}}</ref> Although multicomponent care and comprehensive geriatric care are more specialized for a person experiencing delirium, several studies have been unable to find evidence showing they reduce the duration of delirium.<ref name="Scottish_Intercollegiate_Guidelines_Network_2019" />

Family, friends, and other caregivers can offer frequent reassurance, tactile and verbal orientation, cognitive stimulation (e.g. regular visits, familiar objects, clocks, calendars, etc.), and means to stay engaged (e.g. making hearing aids and eyeglasses readily available).<ref name="Inouye2006" /><ref name="NICE" /><ref>{{cite journal | vauthors = Rudolph JL, Marcantonio ER | title = Review articles: postoperative delirium: acute change with long-term implications | journal = Anesthesia and Analgesia | volume = 112 | issue = 5 | pages = 1202–1211 | date = May 2011 | pmid = 21474660 | pmc = 3090222 | doi = 10.1213/ANE.0b013e3182147f6d }}</ref> Sometimes verbal and non-verbal deescalation techniques may be required to offer reassurances and calm the person experiencing delirium.<ref name="NICE" /> Restraints should rarely be used as an intervention for delirium.<ref name="DeWitt_2018" /> The use of restraints has been recognized as a risk factor for injury and aggravating symptoms, especially in older hospitalized people with delirium.<ref name="DeWitt_2018" /> The only cases where restraints should sparingly be used during delirium is in the protection of life-sustaining interventions, such as endotracheal tubes.<ref name="DeWitt_2018">{{Citation| vauthors = DeWitt MA, Tune LE |title=Delirium|date=2018-07-06|work=The American Psychiatric Association Publishing Textbook of Neuropsychiatry and Clinical Neurosciences|publisher=American Psychiatric Association Publishing|doi=10.1176/appi.books.9781615372423.sy08|isbn=978-1-61537-187-7 |s2cid=240363328}}</ref>

Another approached called the "T-A-DA (''tolerate, anticipate, don't agitate'') method" can be an effective management technique for older people with delirium, where abnormal behaviors (including hallucinations and delusions) are tolerated and unchallenged, as long as caregiver safety and the safety of the person experiencing delirium is not threatened.<ref name="Oh_2017"/> Implementation of this model may require a designated area in the hospital. All unnecessary attachments are removed to anticipate for greater mobility, and agitation is prevented by avoiding excessive reorientation/questioning.<ref name="Oh_2017"/>

===Medications===

The use of medications for delirium is generally restricted to managing its distressing or dangerous neuropsychiatric disturbances. Short-term use (one week or less) of low-dose [[haloperidol]] is among the more common pharmacological approaches to delirium.<ref name="Inouye2006" /><ref name="NICE" /> Evidence for effectiveness of [[atypical antipsychotic]]s (e.g. [[risperidone]], [[olanzapine]], ziprasidone, and [[quetiapine]]) is emerging, with the benefit for fewer side effects<ref name="Inouye2006" /><ref>{{cite book| vauthors = Tyrer PJ, Silk KR |title=Cambridge Textbook of Effective Treatments in Psychiatry |date=2008 |publisher=Cambridge University Press |isbn=9780511393020 |location=Leiden |oclc=437204638}}</ref> Use antipsychotic drugs with caution or not at all for people with conditions such as [[Parkinson's disease]] or [[dementia with Lewy bodies]].<ref name = NICE /> Evidence for the effectiveness of medications (including [[antipsychotic]]s and [[benzodiazepine]]s) in treating delirium is weak.<ref name="Soiza_2019">{{cite journal | vauthors = Soiza RL, Myint PK | title = The Scottish Intercollegiate Guidelines Network (SIGN) 157: Guidelines on Risk Reduction and Management of Delirium | journal = Medicina | volume = 55 | issue = 8 | pages = 491 | date = August 2019 | pmid = 31443314 | pmc = 6722546 | doi = 10.3390/medicina55080491 | doi-access = free }}</ref><ref name="Burry_2019" />

Benzodiazepines can cause or worsen delirium, and there is no reliable evidence of efficacy for treating non-anxiety-related delirium.<ref name="Challenges of Delirium Management i">{{cite journal | vauthors = Roberson SW, Patel MB, Dabrowski W, Ely EW, Pakulski C, Kotfis K | title = Challenges of Delirium Management in Patients with Traumatic Brain Injury: From Pathophysiology to Clinical Practice | journal = Current Neuropharmacology | volume = 19 | issue = 9 | pages = 1519–1544 | date = 2021-09-14 | pmid = 33463474 | pmc = 8762177 | doi = 10.2174/1570159X19666210119153839 }}</ref> Similarly, people with [[dementia with Lewy bodies]] may have significant side effects with antipsychotics, and should either be treated with a none or small doses of benzodiazepines.<ref name="NICE" />

The antidepressant [[trazodone]] is occasionally used in the treatment of delirium, but it carries a risk of over-sedation, and its use has not been well studied.<ref name=Inouye2006/>

For adults with delirium that are in the ICU, medications are used commonly to improve the symptoms. [[Dexmedetomidine]] may shorten the length of the delirium in adults who are critically ill, and [[rivastigmine]] is not suggested.<ref name="Burry_2019" /> For adults with delirium who are near the end of their life (on palliative care) high quality evidence to support or refute the use of most medications to treat delirium is not available.<ref name="Finucane_2020">{{cite journal | vauthors = Finucane AM, Jones L, Leurent B, Sampson EL, Stone P, Tookman A, Candy B | title = Drug therapy for delirium in terminally ill adults | journal = The Cochrane Database of Systematic Reviews | volume = 1 | issue = 1 | pages = CD004770 | date = January 2020 | pmid = 31960954 | pmc = 6984445 | doi = 10.1002/14651858.CD004770.pub3 }}</ref> Low quality evidence indicates that the [[antipsychotic medication]]s risperidone or haloperidol may make the delirium slightly worse in people who are terminally ill, when compared to a [[placebo]] treatment.<ref name="Finucane_2020" /> There is also moderate to low quality evidence to suggest that haloperidol and risperidone may be associated with a slight increase in side effects, specifically [[Extrapyramidal symptoms|extrapyramidal]] symptoms, if the person near the end of their life has delirium that is mild to moderate in severity.<ref name="Finucane_2020" />

==Prognosis==
There is substantial evidence that delirium results in long-term poor outcomes in older persons admitted to hospital.<ref name="Witlox">{{cite journal | vauthors = Witlox J, Eurelings LS, de Jonghe JF, Kalisvaart KJ, Eikelenboom P, van Gool WA | title = Delirium in elderly patients and the risk of postdischarge mortality, institutionalization, and dementia: a meta-analysis | journal = JAMA | volume = 304 | issue = 4 | pages = 443–451 | date = July 2010 | pmid = 20664045 | doi = 10.1001/jama.2010.1013 | s2cid = 13402729 }}</ref> This systematic review only included studies that looked for an independent effect of delirium (i.e., after accounting for other associations with poor outcomes, for example co-morbidity or illness severity).

In older persons admitted to hospital, individuals experiencing delirium are twice as likely to die than those who do not (meta-analysis of 12 studies).<ref name="Witlox" /> In the only prospective study conducted in the general population, older persons reporting delirium also showed higher mortality (60% increase).<ref name="Davis">{{cite journal | vauthors = Davis DH, Muniz Terrera G, Keage H, Rahkonen T, Oinas M, Matthews FE, Cunningham C, Polvikoski T, Sulkava R, MacLullich AM, Brayne C | title = Delirium is a strong risk factor for dementia in the oldest-old: a population-based cohort study | journal = Brain | volume = 135 | issue = Pt 9 | pages = 2809–2816 | date = September 2012 | pmid = 22879644 | pmc = 3437024 | doi = 10.1093/brain/aws190 }}</ref> A large (N=82,770) two-centre study in unselected older emergency population found that delirium detected as part of normal care using the [[4AT]] tool was strongly linked to 30-day mortality, hospital length of stay, and days at home in the year following the 4AT test date.<ref>{{cite journal | vauthors = Anand A, Cheng M, Ibitoye T, Maclullich AM, Vardy ER | title = Positive scores on the 4AT delirium assessment tool at hospital admission are linked to mortality, length of stay and home time: two-centre study of 82,770 emergency admissions | journal = Age and Ageing | volume = 51 | issue = 3 | pages = afac051 | date = March 2022 | pmid = 35292792 | pmc = 8923813 | doi = 10.1093/ageing/afac051 }}</ref>

Institutionalization was also twice as likely after an admission with delirium (meta-analysis of seven studies).<ref name="Witlox" /> In a community-based population examining individuals after an episode of severe infection (though not specifically delirium), these persons acquired more functional limitations (i.e., required more assistance with their care needs) than those not experiencing infection.<ref>{{cite journal | vauthors = Iwashyna TJ, Ely EW, Smith DM, Langa KM | title = Long-term cognitive impairment and functional disability among survivors of severe sepsis | journal = JAMA | volume = 304 | issue = 16 | pages = 1787–1794 | date = October 2010 | pmid = 20978258 | pmc = 3345288 | doi = 10.1001/jama.2010.1553 }}</ref> After an episode of delirium in the general population, functional dependence increased threefold.<ref name="Davis" />

The association between delirium and dementia is complex. The systematic review estimated a 13-fold increase in dementia after delirium (meta-analysis of two studies).<ref name="Witlox" /> However, it is difficult to be certain that this is accurate because the population admitted to hospital includes persons with undiagnosed dementia (i.e., the dementia was present before the delirium, rather than caused by it). In prospective studies, people hospitalised from any cause appear to be at greater risk of dementia<ref name="Ehlenbach">{{cite journal | vauthors = Ehlenbach WJ, Hough CL, Crane PK, Haneuse SJ, Carson SS, Curtis JR, Larson EB | title = Association between acute care and critical illness hospitalization and cognitive function in older adults | journal = JAMA | volume = 303 | issue = 8 | pages = 763–770 | date = February 2010 | pmid = 20179286 | pmc = 2943865 | doi = 10.1001/jama.2010.167 }}</ref> and faster trajectories of cognitive decline,<ref name="Ehlenbach" /><ref>{{cite journal | vauthors = Wilson RS, Hebert LE, Scherr PA, Dong X, Leurgens SE, Evans DA | title = Cognitive decline after hospitalization in a community population of older persons | journal = Neurology | volume = 78 | issue = 13 | pages = 950–956 | date = March 2012 | pmid = 22442434 | pmc = 3310309 | doi = 10.1212/WNL.0b013e31824d5894 }}</ref> but these studies did not specifically look at delirium. In the only population-based prospective study of delirium, older persons had an eight-fold increase in dementia and faster cognitive decline.<ref name="Davis" /> The same association is also evident in persons already diagnosed with Alzheimer's dementia.<ref>{{cite journal | vauthors = Fong TG, Jones RN, Shi P, Marcantonio ER, Yap L, Rudolph JL, Yang FM, Kiely DK, Inouye SK | title = Delirium accelerates cognitive decline in Alzheimer disease | journal = Neurology | volume = 72 | issue = 18 | pages = 1570–1575 | date = May 2009 | pmid = 19414723 | pmc = 2677515 | doi = 10.1212/WNL.0b013e3181a4129a }}</ref>

Recent long-term studies showed that many people still meet criteria for delirium for a prolonged period after hospital discharge, with up to 21% of people showing persistent delirium at 6 months post-discharge.<ref>{{cite journal | vauthors = Cole MG, Ciampi A, Belzile E, Zhong L | title = Persistent delirium in older hospital patients: a systematic review of frequency and prognosis | journal = Age and Ageing | volume = 38 | issue = 1 | pages = 19–26 | date = January 2009 | pmid = 19017678 | doi = 10.1093/ageing/afn253 | doi-access = free }}</ref>

===Dementia in ICU survivors===
{{see also|Post-intensive care syndrome}}
Between 50% and 70% of people admitted to the ICU have permanent problems with brain dysfunction similar to those experienced by people with Alzheimer's or those with a traumatic brain injury, leaving many ICU survivors permanently disabled.<ref>{{cite journal | vauthors = Hopkins RO, Jackson JC | title = Long-term neurocognitive function after critical illness | journal = Chest | volume = 130 | issue = 3 | pages = 869–878 | date = September 2006 | pmid = 16963688 | doi = 10.1378/chest.130.3.869 | s2cid = 8118025 }}</ref> This is a distressing personal and public health problem and continues to receive increasing attention in ongoing investigations.<ref name="Harris_2018">{{Cite web | vauthors = Harris R |date=October 10, 2018 |title=When ICU Delirium Leads To Symptoms Of Dementia After Discharge |url=https://www.npr.org/sections/health-shots/2018/10/10/654445929/when-icu-delirium-leads-to-symptoms-of-dementia-after-discharge |access-date=January 24, 2024 |website=NPR}}</ref><ref name="Challenges of Delirium Management i"/>

The implications of such an "acquired dementia-like illness" can profoundly debilitate a person's livelihood level, often dismantling his/her life in practical ways like impairing one's ability to find a car in a parking lot, complete shopping lists, or perform job-related tasks done previously for years.<ref name="Harris_2018" /> The societal implications can be enormous when considering work-force issues related to the inability of wage-earners to work due to their own ICU stay or that of someone else they must care for.<ref>{{cite web |url=https://www.npr.org/sections/health-shots/2018/10/10/654445929/when-icu-delirium-leads-to-symptoms-of-dementia-after-discharge |title=When ICU Delirium Leads To Symptoms Of Dementia After Discharge | vauthors = Harris R |publisher=National Public Radio |date=October 10, 2018 |access-date=29 April 2019 |archive-date=4 May 2019 |archive-url=https://web.archive.org/web/20190504063245/https://www.npr.org/sections/health-shots/2018/10/10/654445929/when-icu-delirium-leads-to-symptoms-of-dementia-after-discharge |url-status=live }}</ref>

== Epidemiology ==
The highest rates of delirium (often 50–75% of people) occur among those who are critically ill in the intensive care unit (ICU).<ref name="icudelirium">{{cite web|url=http://www.icudelirium.org|title=ICU Delirium and Cognitive Impairment Study Group |publisher= Vanderbilt University Medical Center|archive-url=https://web.archive.org/web/20131010082059/http://www.icudelirium.org/|archive-date=10 October 2013|url-status=live|access-date=6 December 2012|display-authors=etal|vauthors=Ely EW}}</ref> This was historically referred to as "ICU psychosis" or "ICU syndrome"; however, these terms are now widely disfavored in relation to the operationalized term ICU delirium. Since the advent of validated and easy-to-implement delirium instruments for people admitted to the ICU such as the Confusion Assessment Method for the ICU (CAM-ICU)<ref name=Ely2001/> and the Intensive Care Delirium Screening Checklist (ICDSC),<ref name=Bergeron2001/> it has been recognized that most ICU delirium is hypoactive, and can easily be missed unless evaluated regularly. The causes of delirium depend on the underlying illnesses, new problems like [[sepsis]] and low oxygen levels, and the sedative and pain medicines that are nearly universally given to all people in the ICU p. Outside the ICU, on hospital wards and in nursing homes, the problem of delirium is also a very important medical problem, especially for older patients.<ref>{{cite journal | vauthors = Ryan DJ, O'Regan NA, Caoimh RÓ, Clare J, O'Connor M, Leonard M, McFarland J, Tighe S, O'Sullivan K, Trzepacz PT, Meagher D, Timmons S | title = Delirium in an adult acute hospital population: predictors, prevalence and detection | journal = BMJ Open | volume = 3 | issue = 1 | pages = e001772 | date = January 2013 | pmid = 23299110 | pmc = 3549230 | doi = 10.1136/bmjopen-2012-001772 }}</ref>

The most recent area of the hospital in which delirium is just beginning to be monitored routinely in many centers is the Emergency Department, where the prevalence of delirium among older adults is about 10%.<ref name="ccsmh.ca">{{cite book|last1=Canadian Coalition for Seniors' Mental Health|title=National Guidelines for Seniors' Mental Health: The Assessment and Treatment of Delirium|date=2006|publisher=Canadian Coalition for Seniors' Mental Health|url=http://www.ccsmh.ca/en/guidelinesUsers.cfm|url-status=dead|archive-url=https://web.archive.org/web/20140908014058/http://www.ccsmh.ca/en/guidelinesUsers.cfm|archive-date=2014-09-08}}</ref> A systematic review of delirium in general medical inpatients showed that estimates of delirium prevalence on admission ranged 10–31%.<ref>{{cite journal | vauthors = Siddiqi N, House AO, Holmes JD | title = Occurrence and outcome of delirium in medical in-patients: a systematic literature review | journal = Age and Ageing | volume = 35 | issue = 4 | pages = 350–364 | date = July 2006 | pmid = 16648149 | doi = 10.1093/ageing/afl005 | doi-access = free }}</ref> About 5–10% of older adults who are admitted to hospital develop a new episode of delirium while in hospital.<ref name="ccsmh.ca"/> Rates of delirium vary widely across general hospital wards.<ref>{{cite journal | vauthors = McCoy TH, Hart KL, Perlis RH | title = Characterizing and predicting rates of delirium across general hospital settings | journal = General Hospital Psychiatry | volume = 46 | pages = 1–6 | date = May 2017 | pmid = 28622808 | doi = 10.1016/j.genhosppsych.2017.01.006 }}</ref> Estimates of the prevalence of delirium in nursing homes are between 10%<ref name="ccsmh.ca"/> and 45%.<ref name="pmid19233058">{{cite journal | vauthors = Voyer P, Richard S, Doucet L, Carmichael PH | title = Detecting delirium and subsyndromal delirium using different diagnostic criteria among demented long-term care residents | journal = Journal of the American Medical Directors Association | volume = 10 | issue = 3 | pages = 181–188 | date = March 2009 | pmid = 19233058 | doi = 10.1016/j.jamda.2008.09.006 }}</ref>

==Society and culture==
Delirium is one of the oldest forms of mental disorder known in medical history.<ref>{{cite journal | vauthors = Berrios GE | title = Delirium and confusion in the 19th century: a conceptual history | journal = The British Journal of Psychiatry | volume = 139 | issue = 5 | pages = 439–449 | date = November 1981 | pmid = 7037094 | doi = 10.1192/bjp.139.5.439 | s2cid = 145585758 }}</ref> The Roman author [[Aulus Cornelius Celsus]] used the term to describe mental disturbance from head trauma or fever in his work ''[[De Medicina]]''.<ref>{{cite journal | vauthors = Adamis D, Treloar A, Martin FC, Macdonald AJ | title = A brief review of the history of delirium as a mental disorder | journal = History of Psychiatry | volume = 18 | issue = 72 Pt 4 | pages = 459–469 | date = December 2007 | pmid = 18590023 | doi = 10.1177/0957154X07076467 | url = https://hal.archives-ouvertes.fr/hal-00570887/document | access-date = 2019-07-09 | url-status = live | s2cid = 24424207 | archive-url = https://web.archive.org/web/20190705211533/https://hal.archives-ouvertes.fr/hal-00570887/document | archive-date = 2019-07-05 }}</ref> Sims (1995, p.&nbsp;31) points out a "superb detailed and lengthy description" of delirium in "The Stroller's Tale" from [[Charles Dickens]]' ''[[The Pickwick Papers]]''.<ref>{{cite book |vauthors=Sims A |title=Symptoms in the mind: an introduction to descriptive psychopathology |publisher=W. B. Saunders |location=Philadelphia |year=2002 |isbn=978-0-7020-2627-0 }}</ref><ref>Dickens C (1837) ''The Pickwick Papers''. Available for free on [[Project Gutenberg]].</ref> Historically, delirium has also been noted for its cognitive sequelae. For instance, the English medical writer [[Philip Barrow]] noted in 1583 that if delirium (or "frensy") resolves, it may be followed by a loss of memory and reasoning power.<ref>{{Cite book| vauthors = Barrough P |url=https://quod.lib.umich.edu/e/eebo/A04936.0001.001/1:6.15?amt2=40;amt3=40;cite1=Barrough;cite1restrict=author;hi=0;rgn=div2;view=fulltext;q1=memory|title=The methode of phisicke conteyning the causes, signes, and cures of invvard diseases in mans body from the head to the foote. VVhereunto is added, the forme and rule of making remedies and medicines, which our phisitians commonly vse at this day, with the proportion, quantitie, & names of {{sic|ech|nolink=y}} medicine.|publisher=By Thomas Vautroullier dwelling in the Blacke-friars by Lud-gate|year=1583|location=London|pages=18|access-date=2020-04-23|archive-date=2020-07-30|archive-url=https://web.archive.org/web/20200730154704/https://quod.lib.umich.edu/e/eebo/A04936.0001.001/1:6.15?amt2=40;amt3=40;cite1=Barrough;cite1restrict=author;hi=0;rgn=div2;view=fulltext;q1=memory|url-status=live}}</ref>

===Costs===
In the US, the cost of a hospital admission for people with delirium is estimated at between $16k and $64k, suggesting the national burden of delirium may range from $38 bn to $150 bn per year (2008 estimate).<ref>{{cite journal | vauthors = Leslie DL, Marcantonio ER, Zhang Y, Leo-Summers L, Inouye SK | title = One-year health care costs associated with delirium in the elderly population | journal = Archives of Internal Medicine | volume = 168 | issue = 1 | pages = 27–32 | date = January 2008 | pmid = 18195192 | pmc = 4559525 | doi = 10.1001/archinternmed.2007.4 }}</ref> In the UK, the cost is estimated as £13k per admission.<ref>{{cite journal | vauthors = Akunne A, Murthy L, Young J | title = Cost-effectiveness of multi-component interventions to prevent delirium in older people admitted to medical wards | journal = Age and Ageing | volume = 41 | issue = 3 | pages = 285–291 | date = May 2012 | pmid = 22282171 | doi = 10.1093/ageing/afr147 | doi-access = free }}</ref>

== References ==
{{reflist|colwidth=30em}}

== Further reading ==
{{refbegin}}
* {{cite book | vauthors = Macdonald A, Lindesay J, Rockwood K |title=Delirium in old age |publisher=Oxford University Press |location=Oxford [Oxfordshire] |year=2002 |isbn=978-0-19-263275-3 }}
* {{cite book| vauthors = Grassi L, Caraceni A |title=Delirium: acute confusional states in palliative medicine|year=2003|publisher=Oxford University Press|location=Oxford|isbn=978-0192631992}}
* {{cite book| veditors = Newman JK, Slater CT |title=Delirium: causes, diagnosis and treatment|year=2012|publisher=Nova Science Publisher's, Inc.|location=Hauppauge, N.Y.|isbn=978-1613242940}}
{{refend}}

== External links ==

{{EB1911 poster|Delirium }}
{{Medical resources
|  DiseasesDB      = 29284
|  ICD10           = {{ICD10|F|05||f|00}}
|  ICD9            = {{ICD9|780.09}}
|  ICDO            =
|  OMIM            =
|  MedlinePlus     = 000740
|  eMedicineSubj   = med
|  eMedicineTopic  = 3006
|  MeshID          = D003693
}}
{{Mental and behavioural disorders|selected = neurological}}

<!-- [the following statistics are outdated and do not necessarily represent the broad range of delirium symptoms across all settings]
The range of clinical features include: poor attention/[[Vigilance (psychology)|vigilance]] (100%), memory impairment (64–100%), clouding of consciousness (45–100%), disorientation (43–100%), acute onset (93%), disorganized thinking/thought disorder (59–95%), diffuse cognitive impairment (77%), language disorder (41–93%), sleep disturbance (25–96%), [[Emotional lability|mood lability]] (43–63%), psychomotor changes (i.e., hyperactive, hypoactive, mixed) (38–55%), delusions (18–68%), and perceptual change/hallucinations (17–55%).<ref name="American_Psychiatric_Publishing_2008" /> -->

<!-- [The RASS and OSLA do not belong here. They evaluate arousal, not delirium.]
* [[Richmond Agitation-Sedation Scale|Richmond Agitation and Sedation Scale]] (RASS) – highly [[Sensitivity and specificity|sensitive and specific]] for diagnosing delirium in older patients<ref name="Burton_2021">{{cite journal | vauthors = Quispel-Aggenbach DW, Holtman GA, Zwartjes HA, Zuidema SU, Luijendijk HJ | title = Attention, arousal and other rapid bedside screening instruments for delirium in older patients: a systematic review of test accuracy studies | journal = Age and Ageing | volume = 47 | issue = 5 | pages = 644–653 | date = September 2018 | pmid = 29697753 | doi = 10.1093/ageing/afy058 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Ely EW, Truman B, Shintani A, Thomason JW, Wheeler AP, Gordon S, Francis J, Speroff T, Gautam S, Margolin R, Sessler CN, Dittus RS, Bernard GR | title = Monitoring sedation status over time in ICU patients: reliability and validity of the Richmond Agitation-Sedation Scale (RASS) | journal = JAMA | volume = 289 | issue = 22 | pages = 2983–91 | date = June 2003 | pmid = 12799407 | doi = 10.1001/jama.289.22.2983 | doi-access = free }}</ref>
* Observational Scale of Level of Arousal (OSLA) – highly [[Sensitivity and specificity|sensitive and specific]] for diagnosing delirium in older patients<ref name="Burton_2021" /><ref>{{cite journal | vauthors = Tieges Z, McGrath A, Hall RJ, Maclullich AM | title = Abnormal level of arousal as a predictor of delirium and inattention: an exploratory study | journal = The American Journal of Geriatric Psychiatry | volume = 21 | issue = 12 | pages = 1244–53 | date = December 2013 | pmid = 24080383 | doi = 10.1016/j.jagp.2013.05.003 }}</ref> -->

[[Category:Delirium| ]]
[[Category:Cognitive disorders]]
[[Category:Intensive care medicine]]
[[Category:Psychopathological syndromes]]
[[Category:Neurocognitive disorders]]