Editing Causes of mental disorders

{{Short description|Etiology of psychopathology}}
{{Mental health sidebar}}
[[File:The prevalence of mental illness is higher in more unequal rich countries.jpg|thumb|Image 1: The prevalence of mental illness is higher in more [[economic inequality|unequal]] rich countries]]
A [[mental disorder]] is an impairment of the mind disrupting normal thinking, feeling, mood, behavior, or [[Social relation|social interactions]], and accompanied by significant distress or dysfunction.<ref>{{Cite web|url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/334423054|title=Mental, behavioural or neurodevelopmental disorders|work=International Classification of Diseases for Mortality and Morbidity Statistics, 11th rev. (ICD-11 MMS)|publisher=World Health Organization|date=April 2019|access-date=2019-10-30|quote=Mental, behavioural and neurodevelopmental disorders are syndromes characterized by clinically significant disturbance in an individual's cognition, emotional regulation, or behaviour that reflects a dysfunction in the psychological, biological, or developmental processes that underlie mental and behavioural functioning. These disturbances are usually associated with distress or impairment in personal, family, social, educational, occupational, or other important areas of functioning.}}</ref><ref>''Webster's Third New International Dictionary'', (Springfield, MA: Merriam-Webster, 1961, rev. 2016), ([[mwod:mental disorder|"mental illness ''noun'']], variants: ''or'' mental disorder ''or less commonly'' mental disease, Definition of mental illness: any of a broad range of medical conditions (such as major depression, schizophrenia, obsessive compulsive disorder, or panic disorder) that are marked primarily by sufficient disorganization of personality, mind, or emotions to impair normal psychological functioning and cause marked distress or disability and that are typically associated with a disruption in typical thinking, feeling, mood, behavior, interpersonal interactions, or daily functioning").</ref><ref>''American Heritage Dictionary of the English Language'', 5th ed. (Boston: Houghton Mifflin Harcourt, 2011, rev. 2018), ([https://ahdictionary.com/word/search.html?q=mental+disorder "mental disorder, ''n''.] - Any of various disorders, such as schizophrenia, bipolar disorder, or autism spectrum disorder, characterized by a distressing or disabling impairment of an individual's cognitive, emotional, or social functioning.")</ref><ref>''Oxford English Dictionary'', 3rd ed. (Oxford, UK: Oxford University Press, September 2001), ("[https://oed.com/view/Entry/116537 II. Senses relating to the mind in an unhealthy or abnormal state. 5. a. Designating a temporary or permanent impairment of the mind] due to inherited defect, injury, illness, or environment, usually needing special care or rehabilitation. Esp. in mental breakdown, mental deficiency, mental disease, mental disorder, mental incapacity, mental retardation, etc.; see also mental illness n. at Compounds. ... mental illness ''n''. a condition which causes serious abnormality in a person's thinking or behaviour, esp. one requiring special care or treatment; a psychiatric illness. <small>Now somewhat dated, and sometimes avoided as being potentially offensive.</small>").</ref> The '''causes of mental disorders''' are very complex and vary depending on the particular disorder and the individual. Although the causes of most mental disorders are not fully understood, researchers have identified a variety of biological, psychological, and [[environmental factors]] that can contribute to the development or progression of mental disorders.<ref>{{cite journal | vauthors = Arango C, Díaz-Caneja CM, McGorry PD, Rapoport J, Sommer IE, Vorstman JA, McDaid D, Marín O, Serrano-Drozdowskyj E, Freedman R, Carpenter W | display-authors = 6 | title = Preventive strategies for mental health | journal = The Lancet. Psychiatry | volume = 5 | issue = 7 | pages = 591–604 | date = July 2018 | pmid = 29773478 | doi = 10.1016/S2215-0366(18)30057-9 | hdl-access = free | s2cid = 21703364 | hdl = 11370/92f1a79c-f53d-47ae-be92-7a4c8d4b4e25 | url = https://research.rug.nl/en/publications/92f1a79c-f53d-47ae-be92-7a4c8d4b4e25 }}</ref> Most mental disorders result in a combination of several different factors rather than just a single factor.<ref name="pmid29211974">{{cite journal | vauthors = Clark LA, Cuthbert B, Lewis-Fernández R, Narrow WE, Reed GM | title = Three Approaches to Understanding and Classifying Mental Disorder: ICD-11, DSM-5, and the National Institute of Mental Health's Research Domain Criteria (RDoC) | journal = Psychological Science in the Public Interest | volume = 18 | issue = 2 | pages = 72–145 | date = September 2017 | pmid = 29211974 | doi = 10.1177/1529100617727266 | quote = ... research has shown that psychopathology generally arises from multiple biological, behavioral, psychosocial, and cultural factors, all interacting in complex ways and filtered through an individual's lifetime of experience. Research also has shown that the outcomes of these factors and their interactions are not clearly definable, distinct diseases, but are instead complex and variable combinations of psychological problems. | s2cid = 206743519 | doi-access = free }}</ref>

==Research results==
Risk factors for mental illness include [[psychological trauma]], adverse childhood experiences, genetic predisposition, and personality traits.<ref>{{Cite journal |last1=Read |first1=John |last2=Bentall |first2=Richard P. |date=February 2012 |title=Negative childhood experiences and mental health: theoretical, clinical and primary prevention implications |url=https://www.cambridge.org/core/product/identifier/S0007125000257516/type/journal_article |journal=British Journal of Psychiatry |language=en |volume=200 |issue=2 |pages=89–91 |doi=10.1192/bjp.bp.111.096727 |pmid=22297585 |issn=0007-1250}}</ref><ref>{{Cite journal |last1=Kurbatfinski |first1=Stefan |last2=Dosani |first2=Aliyah |last3=Dewey |first3=Deborah M. |last4=Letourneau |first4=Nicole |date=2024-09-12 |title=Proposed Physiological Mechanisms Underlying the Association between Adverse Childhood Experiences and Mental Health Conditions: A Narrative Review |journal=Children |language=en |volume=11 |issue=9 |pages=1112 |doi=10.3390/children11091112 |doi-access=free |issn=2227-9067 |pmc=11430311 |pmid=39334644}}</ref> Correlations between mental disorders and substance use are also found to have a two way relationship, in that substance use can lead to the development of mental disorders and having mental disorders can lead to substance use/abuse. This effect is stronger and more reliable in some substance use than others, such as smoking.<ref>{{Cite journal |last1=Treur |first1=Jorien L. |last2=Munafò |first2=Marcus R. |last3=Logtenberg |first3=Emma |last4=Wiers |first4=Reinout W. |last5=Verweij |first5=Karin J. H. |date=July 2021 |title=Using Mendelian randomization analysis to better understand the relationship between mental health and substance use: a systematic review |journal=Psychological Medicine |language=en |volume=51 |issue=10 |pages=1593–1624 |doi=10.1017/S003329172100180X |issn=0033-2917 |pmc=8327626 |pmid=34030749}}</ref>

Mental illnesses have risk factors, for instance including unequal parental treatment, adverse life events and drug use in [[Depression (mood)|depression]], migration and discrimination, childhood trauma, loss or separation in families, and cannabis use in [[schizophrenia]] and [[psychosis]], and parenting factors, child abuse, family history (e.g. of anxiety), and temperament and attitudes (e.g. pessimism) in [[anxiety]]. Many psychiatric disorders include problems with [[Impulse control disorder|impulse and other emotional control]].

In February 2013, a study <ref>{{cite web |author=<!-- not stated --> |date= March 18, 2013 |title= Common Genetic Factors Found in 5 Mental Disorders |url= https://www.nih.gov/news-events/nih-research-matters/common-genetic-factors-found-5-mental-disorders |website= |location= |publisher= National Institutes of Health |access-date= 2025-05-11}}</ref> found genetic links between five major psychiatric disorders: [[autism]], [[ADHD]], [[bipolar disorder]], [[major depressive disorder]], and [[schizophrenia]]. Abnormal functioning of [[neurotransmitter]] systems is also responsible for some mental disorders, including serotonin, norepinephrine, dopamine, and glutamate system's abnormal functioning. Differences have also been found in the size or activity of specific brain regions in some cases. Psychological mechanisms have also been implicated, such as [[cognitive]] (e.g. [[reasoning]]) biases, [[emotional]] influences, [[Personality psychology|personality dynamics]], [[temperament]], and [[Coping (psychology)|coping]] style. Studies have indicated<ref name="Journal of Psychiatric Research 2015 pp. 1–13">{{cite journal | vauthors = Gatt JM, Burton KL, Williams LM, Schofield PR | title = Specific and common genes implicated across major mental disorders: a review of meta-analysis studies | journal = Journal of Psychiatric Research | volume = 60 | pages = 1–13 | date = January 2015 | pmid = 25287955 | doi = 10.1016/j.jpsychires.2014.09.014 }}</ref> that variation in [[genes]] can play an important role in the evolution of mental disorders, although the reliable identification of connections between specific genes and specific disorders has proven more difficult. Environmental events surrounding [[pregnancy]] (such as maternal [[hypertension]],<ref name="Lahti-Pulkkinen Girchenko Tuovinen Sammallahti 2020 pp. 1429–1438">{{cite journal | vauthors = Lahti-Pulkkinen M, Girchenko P, Tuovinen S, Sammallahti S, Reynolds RM, Lahti J, Heinonen K, Lipsanen J, Hämäläinen E, Villa PM, Kajantie E, Laivuori H, Räikkönen K | display-authors = 6 | title = Maternal Hypertensive Pregnancy Disorders and Mental Disorders in Children | journal = Hypertension | volume = 75 | issue = 6 | pages = 1429–1438 | date = June 2020 | pmid = 32306771 | doi = 10.1161/hypertensionaha.119.14140 | publisher = Ovid Technologies (Wolters Kluwer Health) | s2cid = 216028720 | doi-access = free | hdl = 20.500.11820/02b77370-a4e8-4dbe-bbcf-879222a3420b | hdl-access = free }}</ref> [[preeclampsia]], or infection) and [[Childbirth|birth]] have also been implicated.<ref name="Rice Harold Boivin Bree 2009 pp. 335–345">{{cite journal | vauthors = Rice F, Harold GT, Boivin J, van den Bree M, Hay DF, Thapar A | title = The links between prenatal stress and offspring development and psychopathology: disentangling environmental and inherited influences | journal = Psychological Medicine | volume = 40 | issue = 2 | pages = 335–345 | date = February 2010 | pmid = 19476689 | pmc = 2830085 | doi = 10.1017/S0033291709005911 | s2cid = 13752317 }}</ref> [[Traumatic brain injury]] may increase the risk of developing certain mental disorders. Throughout the years, there have been inconsistent links found to certain viral infections, substance misuse, and general physical health that have been false.

Adverse experiences affect a person's [[mental health]], including [[abuse]], [[neglect]], [[bullying]], [[social stress]], [[Traumatic event (psychological)|traumatic events]], and other overwhelming life experiences. The specific risks and pathways to particular disorders are less clear, however. Aspects of the wider community have also been implicated, including [[employment]] problems, [[socioeconomic]] [[Economic inequality|inequality]], lack of social cohesion, problems linked to [[Human migration|migration]], and features of particular [[societies]] and [[cultures]]. The loss of cultural connection can result in [[cultural bereavement]].<ref name=":1">{{cite journal | vauthors = Bhugra D, Becker MA | title = Migration, cultural bereavement and cultural identity | journal = World Psychiatry | volume = 4 | issue = 1 | pages = 18–24 | date = February 2005 | pmid = 16633496 | pmc = 1414713 }}</ref> Mental stress is a common cause of mental illnesses, so finding a coping solution to cope with mental [[Psychological stress|stress]] would be beneficial. Many solutions that have helped reduce stress are yoga, exercise, and some medications that may help.

==Theories==

===General theories===
{{no sources section|date=October 2024}}
Several [[theories]] or [[scientific modelling|models]] seek to explain the causes ([[etiology]]) of [[mental disorder]]s. These theories may differ in regards to how they explain the cause of the disorder, how to treat the disorder, and how they [[classification of mental disorders|classify mental disorders]]. Theories also differ about the [[philosophy of mind]] they accept; that is, whether the [[mind]] and [[brain]] are identical or not. {{cn|date=October 2024}}

During most of the 20th century, mental illness was ascribable to problematic relationships between children and their parents. This view was held well into the late 1990s, in which people still believed this child-parent relationship was a large determinant of severe mental illness, such as depression and schizophrenia. In the 21st century, additional factors have been identified such as genetic contributions, though experience also plays a role. So, the perceived causes of mental illness have changed over time and will most likely continue to alter while more research develops throughout the years.

Outside the West, community approaches remain a focus.{{cn|date=October 2024}}

A practical mixture of models will explain particular issues and disorders, although there may be difficulty defining boundaries for indistinct psychiatric [[syndromes]].

===Medical or biomedical model===
An overall distinction is also commonly made between a "medical model" (also known as a biomedical or disease model) and a "social model" (also known as an empowerment or recovery model) of mental disorder and [[disability]], with the former focusing on hypothesized disease processes and symptoms, along with latter focusing on hypothesized [[social constructionism]] and social contexts.

[[Biological psychiatry]] has tended to follow a [[biomedical]] model focused on organic or "hardware" pathology of the brain,<ref name="Ghaemi 2006">{{cite journal | vauthors = Ghaemi SN | title = Paradigms of psychiatry: eclecticism and its discontents | journal = Current Opinion in Psychiatry | volume = 19 | issue = 6 | pages = 619–624 | date = November 2006 | pmid = 17012942 | doi = 10.1097/01.yco.0000245751.98749.52 | s2cid = 22068456 }}</ref> where many mental disorders are conceptualized as disorders of [[brain circuits]] shaped by a complex interplay of genetics and experience.<ref name=Insel>{{cite journal | vauthors = Insel TR, Wang PS | title = Rethinking mental illness | journal = JAMA | volume = 303 | issue = 19 | pages = 1970–1971 | date = May 2010 | pmid = 20483974 | doi = 10.1001/jama.2010.555 | s2cid = 8210144 }}</ref>

The social and medical models of mental disorders each work to identify and study distinct aspects, solutions, and potential therapies of disorders. The intersection and cross reference between the two models can further be used to develop more holistic models of mental disorders. Many criticisms historically of each model is the exclusivity of the other perspective. Therefore, intersectional research improved the impact and importance of future findings.<ref>Hogan A. J. (2019). Social and medical models of disability and mental health: evolution and renewal. CMAJ: Canadian Medical Association journal, 191(1), E16–E18. https://doi.org/10.1503/cmaj.181008</ref>

===Biopsychosocial model===
The primary model of contemporary mainstream Western psychiatry is the [[biopsychosocial model]] (BPS), which integrates biological, psychological, and social factors.<ref name="Ghaemi 2006" /> The Biopsychosocial model was first conceptualised by George Engel in 1977,<ref>{{cite journal | vauthors = Engel GL | title = The need for a new medical model: a challenge for biomedicine | journal = Science | volume = 196 | issue = 4286 | pages = 129–136 | date = April 1977 | pmid = 847460 | doi = 10.1126/science.847460 | bibcode = 1977Sci...196..129E }}</ref> suggesting that to understand a person's medical condition it is not simply the biological factors to consider, but also the psychological and social factors . The biopsychosocial approach systematically considers biological, psychological, and social factors and their complex interactions in understanding health, illness, and health care delivery. Biological, psychological, and social factors exist along a continuum of natural systems. The factors within the model contain the following:

* Biological (physiological pathology)
* Psychological (thoughts emotions and behaviours such as psychological distress, fear/avoidance beliefs, current coping methods and attribution)
* Social (socio-economical, socio-environmental, and cultural factors such as work issues, family circumstances and benefits/economics)

This model is commonly used for case conceptualization of psychological disorders as well as chronic pain,<ref>{{cite journal | vauthors = Miaskowski C, Blyth F, Nicosia F, Haan M, Keefe F, Smith A, Ritchie C | title = A Biopsychosocial Model of Chronic Pain for Older Adults | journal = Pain Medicine | volume = 21 | issue = 9 | pages = 1793–1805 | date = September 2020 | pmid = 31846035 | doi = 10.1093/pm/pnz329 }}</ref> with the view that the pain is a psychophysiological behavior pattern that cannot be categorised into biological, psychological, or social factors alone. 

A related view, the [[diathesis-stress model]], posits that mental disorders result from genetic dispositions and environmental stressors, combining to cause patterns of distress or dysfunction.<ref>{{cite book | vauthors = Murthy RS |display-authors= etal |title=The World Health Report 2001: Mental Health, New Understanding, New Hope|orig-year=2001 |date= 2002 |publisher=World Health Organization|location=Geneva|edition= Reprint|url=https://books.google.com/books?id=GQEdA-VFSIgC&q=mental+health+comes+from+genetics&pg=PR9 |isbn= 9789241562010}}</ref> The model is one way to explain why some individuals are more vulnerable to mental disorders than others. Additionally, it explains why some people may develop a mental disorder after exposure to stressful life events while others do not.

===Psychoanalytic theories===
[[Psychoanalytic]] theories focus on unresolved internal and relational conflicts. These theories have been predicated as explanations of mental disorders. Many psychoanalytic groups are said to adhere to the biopsychosocial model and to accept an eclectic mix of subtypes of psychoanalysis. [[Sigmund Freud]] developed the psychoanalytic theory. This theory focuses on the impact of unconscious forces on human behavior. According to Freud, a personality has three parts: the [[Id, ego and super-ego|id]], [[Id, ego and super-ego#Ego|ego]], and [[superego]]. The id operates under the [[Pleasure principle (psychology)|pleasure principle]], the ego operates under the [[reality principle]], and the superego is the "conscience" and incorporates what is and is not socially acceptable into a person's value system.<ref>{{Cite book | vauthors = Nyongesa A |url=http://www.jstor.org/stable/j.ctvh9vxtv |title=Tintinnabulation of Literary Theory: Traversing Genres to Contemporary Experience |date=2018-09-23 |publisher=Mwanaka Media and Publishing |isbn=978-1-77906-514-8 |doi=10.2307/j.ctvh9vxtv.8|jstor=j.ctvh9vxtv |s2cid=239252932 }}</ref> According to the psychoanalytic theory, there are five stages of psychosexual development that everyone goes through the [[oral stage]], [[anal stage]], [[phallic stage]], [[latency stage]], and [[genital stage]]. Mental disorders can be caused by an individual receiving too little or too much gratification in one of the psychosexual developmental stages. When this happens, the individual is said to be in that developmental stage.<ref>{{cite journal | vauthors = Saygin D, Tabib T, Bittar HE, Valenzi E, Sembrat J, Chan SY, Rojas M, Lafyatis R | display-authors = 6 | title = Transcriptional profiling of lung cell populations in idiopathic pulmonary arterial hypertension | journal = Pulmonary Circulation | volume = 10 | issue = 1 | pages = 54–77 | date = 2005 | pmid = 32166015 | doi = 10.1111/j.1527-2001.2005.tb00373.x | pmc = 7052475 | s2cid = 143641177 }}</ref>

=== Attachment theory ===
[[Attachment theory]] is a kind of evolutionary-psychological approach sometimes applied in the context of mental disorders, which focuses on the role of early caregiver-child relationships, responses to danger, and the search for a satisfying reproductive relationship in adulthood. According to this theory, a child's attachment is to a nurturing adult, the more likely that child will maintain healthy relationships with others in their life.<ref>{{cite journal | vauthors = Keller H | title = Universality claim of attachment theory: Children's socioemotional development across cultures | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 115 | issue = 45 | pages = 11414–11419 | date = November 2018 | pmid = 30397121 | pmc = 6233114 | doi = 10.1073/pnas.1720325115 | bibcode = 2018PNAS..11511414K | doi-access = free }}</ref> As found by the [[Strange situation|Strange Situation experiment]] run by [[Mary Ainsworth]] based on the formulations of [[John Bowlby]], there are four patterns of attachment: [[secure attachment]], [[Attachment styles|avoidant attachment]], [[disorganized attachment]], and [[ambivalent attachment]].<ref name=":0">{{cite journal | vauthors = Waters E, Hamilton CE, Weinfield NS | title = The stability of attachment security from infancy to adolescence and early adulthood: general introduction | journal = Child Development | volume = 71 | issue = 3 | pages = 678–683 | date = 2000 | pmid = 10953933 | doi = 10.1111/1467-8624.00175 | jstor = 1132385 }}</ref> Later research found the fourth pattern of attachment is known as [[Disorganized attachment|disorganized disoriented attachment]].<ref>{{cite journal | vauthors = Fearon RP, Bakermans-Kranenburg MJ, van Ijzendoorn MH, Lapsley AM, Roisman GI | title = The significance of insecure attachment and disorganization in the development of children's externalizing behavior: a meta-analytic study | journal = Child Development | volume = 81 | issue = 2 | pages = 435–456 | date = 2010 | pmid = 20438450 | doi = 10.1111/j.1467-8624.2009.01405.x | jstor = 40598991 | url = https://centaur.reading.ac.uk/17513/1/Fearon_et_al.%2C_2010.pdf }}</ref> Secure attachments reflect trust in the child-caretaker relationship while insecure attachment reflects mistrust. The security of attachment in a child affects the child's emotional, cognitive, and social competence later in life.<ref name=":0" />

===Evolutionary psychology===
{{See also|Evolutionary psychiatry}}
[[Evolutionary psychology]] and [[evolutionary psychiatry]] posit that mental disorders involve the dysfunctional operation of [[mental module]]s adapted to [[ancestral]] physical or social environments but not necessarily to modern ones. Behavioral abnormalities that resemble human mental illness have been found in related species ([[great apes]]).

Other theories suggest that mental illness could have evolutionary ''advantages'' for the species, including enhancing creativity<ref>{{Cite journal |last1=Nettle |first1=Daniel |last2=Clegg |first2=Helen |date=2006-03-07 |title=Schizotypy, creativity and mating success in humans |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=273 |issue=1586 |pages=611–615 |doi=10.1098/rspb.2005.3349 |issn=0962-8452 |pmc=1560060 |pmid=16537133}}</ref> and [[Stress (biology)|stress]] to enhance survival by activating the [[flight-or-fight response]] in anticipation of danger.

[[Mania]] and [[Depression (mood)|depression]] could have benefited from seasonal changes by helping to increase energy levels during times of plenty and rejuvenating energy during times of scarcity. In this way, mania was set in motion during the spring and summer to facilitate energy for hunting; depression worked best during the winter, similar to how bears [[hibernate]] to recover their energy levels.<ref>{{Cite journal |last1=Rantala |first1=Markus J. |last2=Luoto |first2=Severi |last3=Krams |first3=Indrikis |last4=Karlsson |first4=Hasse |date=2018-03-01 |title=Depression subtyping based on evolutionary psychiatry: Proximate mechanisms and ultimate functions |url=https://www.sciencedirect.com/science/article/pii/S0889159117304683 |journal=Brain, Behavior, and Immunity |language=en |volume=69 |pages=603–617 |doi=10.1016/j.bbi.2017.10.012 |pmid=29051086 |s2cid=3975281 |issn=0889-1591}}</ref> This may explain the connection between circadian genes and [[Bipolar Disorder]] and explain the relationship between light and [[seasonal affective disorder]].

==Biological factors==
Biological factors consist of anything physical that can cause adverse effects on a person's mental health. Biological factors include genetics, prenatal damage, infections, exposure to toxins, brain defects or injuries, and substance abuse. Many professionals believe that the cause of mental disorders is the biology of the brain and the nervous system.{{cn|date=October 2024}}

[[Mind (charity)|''Mind'']] mentions genetic factors, long-term physical health conditions, and head injuries or epilepsy (affecting behavior and mood) as factors that may trigger an episode of mental illness.

===Genetics===

Some rare mental disorders are caused only by genetics such as [[Huntington's disease]].

Family linkage and some [[twin studies]] have indicated that [[psychiatric genetics|genetic factors often play a role]] in the heritability of mental disorders. The reliable identification of specific genetic variation can cause indication of higher risk to particular disorders, through [[Genetic linkage|linkage]], Genome Wide Association Scores<ref>https://www.genome.gov/genetics-glossary/Genome-Wide-Association-Studies Genome-wide association studies (GWAS). Genome.gov. (n.d.). Retrieved August 8, 2022</ref> or [[Genetic association|association studies]], has proven difficult. This is due to the complexity of interactions between genes, environmental events, and early development or the need for new research strategies. No specific gene results in a complex trait disorder, but specific variations of alleles result in higher risk for a trait. The [[heritability]] of behavioral traits associated with a mental disorder may be in permissive than in restrictive environments, and susceptibility genes probably work through both "within-the-skin" (physiological) pathways and "outside-the-skin" (behavioral and social) pathways. Investigations increasingly focus on links between genes and endophenotypes because they are more specific traits. Some include neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, or neuropsychological, rather than disease categories. Concerning a well-known mental disorder, [[schizophrenia]], it is said with certainty {{by whom|date=October 2024}} that [[alleles]] (forms of genes) were responsible for this disorder. Some research has indicated only multiple, rare mutations are thought to alter neurodevelopmental pathways that can ultimately contribute to schizophrenia; virtually every rare structural mutation was different in each individual.{{cn|date=October 2024}}

Research has shown that many conditions are polygenic meaning there are multiple defective genes rather than only one that is responsible for a disorder, and these genes may also be pleiotropic meaning that they cause multiple disorders, not just one.<ref>{{cite journal | vauthors = Lu H, Qiao J, Shao Z, Wang T, Huang S, Zeng P | title = A comprehensive gene-centric pleiotropic association analysis for 14 psychiatric disorders with GWAS summary statistics | journal = BMC Medicine | volume = 19 | issue = 1 | pages = 314 | date = December 2021 | pmid = 34895209 | pmc = 8667366 | doi = 10.1186/s12916-021-02186-z | doi-access = free }}</ref> [[Schizophrenia]] and [[Alzheimer's]] are both examples of hereditary mental disorders.{{cn|date=March 2025}} When exonic genes encode for proteins, these proteins do not just affect one trait. The pathways that contribute to complex traits and phenotypes interact with multiple systems, even though proteins have specific functions.<ref>Lynch M. (2005). Simple evolutionary pathways to complex proteins. Protein science: a publication of the Protein Society, 14(9), 2217–2227. https://doi.org/10.1110/ps.041171805</ref> 
[[Neuroplasticity|brain plasticity (neuroplasticity)]] raises questions of whether some brain differences may be caused by mental illnesses or by pre-existing and then causing them.
====Attention deficit hyperactivity disorder====
{{excerpt|Attention deficit hyperactivity disorder|Genetics}}
====Bipolar disorder====
{{excerpt|Bipolar disorder|Genetic}}

===Prenatal damage===
Any damage that occurs to a fetus while still in its mother's womb is considered prenatal damage. Mental disorders can develop if the pregnant mother uses drugs or alcohol or is exposed to illnesses or infections during pregnancy. {{cn|date=October 2024}}
Environmental events surrounding [[pregnancy]] and [[Childbirth|birth]] have increased the development of mental illness in the [[offspring]]. Some events may include maternal exposure to [[Stress (medicine)|stress]] or [[Psychological trauma|trauma]], conditions of famine, [[Obstetric|obstetric birth]] complications, infections, and [[Pregnancy|gestational]] exposure to [[Alcohol (drug)|alcohol]] or [[cocaine]]. These factors have been hypothesized to affect areas of neurodevelopment, general development, and restrict [[neuroplasticity]].{{cn|date=October 2024}}

===Infection, disease and toxins===
====Infection====
There have been some findings of links between infection by the parasite [[Toxoplasma gondii]] and schizophrenia.<ref name="Contopoulos-Ioannidis Gianniki Ai-Nhi Truong Montoya 2022 pp. 48–60">{{cite journal | vauthors = Contopoulos-Ioannidis DG, Gianniki M, Ai-Nhi Truong A, Montoya JG | title = Toxoplasmosis and Schizophrenia: A Systematic Review and Meta-Analysis of Prevalence and Associations and Future Directions | journal = Psychiatric Research and Clinical Practice | volume = 4 | issue = 2 | pages = 48–60 | year = 2022 | pmid = 36254187 | doi = 10.1176/appi.prcp.20210041 | publisher = American Psychiatric Association Publishing | pmc = 9558922 | s2cid = 248354624 }}</ref>

[[Signs and symptoms of HIV/AIDS#Neurological and psychiatric|AIDS]] has been linked to some mental disorders. Research shows that infections and exposure to toxins such as [[HIV]]<ref name=HIV/> and [[streptococcus]] cause dementia.<ref>{{cite journal | vauthors = Ebert S, Goos M, Rollwagen L, Baake D, Zech WD, Esselmann H, Wiltfang J, Mollenhauer B, Schliebs R, Gerber J, Nau R | display-authors = 6 | title = Recurrent systemic infections with Streptococcus pneumoniae do not aggravate the course of experimental neurodegenerative diseases | journal = Journal of Neuroscience Research | volume = 88 | issue = 5 | pages = 1124–1136 | date = April 2010 | pmid = 19859962 | doi = 10.1002/jnr.22270 | s2cid = 35148634 }}</ref> This HIV infection that makes its way to the brain is called encephalopathy which spreads itself through the brain leading to dementia.<ref name=HIV>{{Cite web |date=2021-08-08 |title=HIV and Dementia | archive-url=https://web.archive.org/web/20200803202732/https://www.hopkinsmedicine.org/health/conditions-and-diseases/hiv-and-aids/hiv-and-dementia  | archive-date=2020-08-03 |url=https://www.hopkinsmedicine.org/health/conditions-and-diseases/hiv-and-aids/hiv-and-dementia |access-date=2022-05-04 |publisher=The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System  | location=Baltimore MD |website=www.hopkinsmedicine.org |language=en}}</ref> The infections or toxins that trigger a change in the brain chemistry can develop into a mental disorder.

Depression and emotional liability may be also be caused by [[babesiosis]].

There is some evidence that there may be a relationship between [[Borna disease#Psychiatric disease|BoDV-1 infection and psychiatric disease]].

The research on Lyme disease caused by a deer tick and toxins is expanding the link between bacterial infections and mental illness.<ref>{{cite web | url=https://www.cugmhp.org/five-on-friday-posts/lyme-disease-and-mental-health/ | title=Lyme Disease and Mental Health | date=17 August 2018 }}</ref>

====Disease====
Depression, anxiety, mania, psychosis, vegetative symptoms, cognitive deficit and consciousness impairment may be caused by internal disease as well as endocrine and metabolic disorders, deficiency states and neurologic disorders.<ref name="A R S L p.">{{cite journal |last1=A |first1=Testa |last2=R |first2=Giannuzzi |last3=S |first3=Daini |last4=L |first4=Bernardini |last5=L |first5=Petrongolo |last6=N |first6=Gentiloni Silveri |title=Psychiatric emergencies (part III): psychiatric symptoms resulting from organic diseases |url=https://pubmed.ncbi.nlm.nih.gov/23436670/ |journal=European Review for Medical and Pharmacological Sciences |date=February 2013 |publisher=Eur Rev Med Pharmacol Sci |volume=17 |issue=Suppl 1 |pages=86–99 |issn=1128-3602 |pmid=23436670 |access-date=2023-08-11}}</ref>

===Injury and brain defects===
{{more sources needed section|date=October 2024}}
Any damage to the brain can cause a mental disorder. The brain is the control system for the nervous system and the rest of the body. Without it, the body cannot function properly.<ref>{{Cite web |title=Brain Death - Brain, Spinal Cord, and Nerve Disorders |url=https://www.msdmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/coma-and-impaired-consciousness/brain-death |access-date=2023-03-24 |website=MSD Manual Consumer Version |language=en}}</ref>

Increased mood swings, insane behavior, and substance abuse disorders are [[traumatic brain injury]] (TBI) examples. Findings on the relationship between TBI severity and prevalence of subsequent psychiatric disorders have been inconsistent, and occurrence relates to prior mental health problems. Direct neurophysiological effects in a complex interaction with personality, attitude, and [[social influences]].

Head trauma classifies as either open or closed head injury. In [[open head injury]], the skull is punctured and the brain tissue is demolished. [[Closed head injury]] is more common, the skull is not punctured because there is an impact of the brain against the skull that creates permanent structural damage ([[subdural hematoma]]). With both types, symptoms may disappear or persist over time. Typically the longer the length of time spent unconscious and the length of [[post-traumatic amnesia]] the worse the prognosis for the individual. The cognitive residual symptoms of head trauma are associated with the type of injury (either an open head injury or closed head injury) and the amount of tissue destroyed. Closed injury head trauma symptoms include; Deficits in [[Abstract reasoning|abstract reasoning ability]], judgment, memory, and marked personality changes. Open injury head trauma symptoms tend to be the experience of classic neuropsychological syndromes like [[aphasia]], visual-spatial disorders, and types of memory or [[Sensory processing disorder|perceptual disorders]].{{cn|date=October 2024}}

[[Brain tumor]]s are classified as either [[malignant]] and [[benign]], and as [[intrinsic]] (directly infiltrate the [[parenchyma]] of the brain) or [[extrinsic]] (grows on the external surface of the brain and produces symptoms as a result of pressure on the brain tissue). Progressive cognitive changes associated with brain tumors may include confusion, poor comprehension, and even [[dementia]]. Symptoms tend to depend on the location of the tumor in the brain. For example, tumors on the [[Frontal lobe|frontal lobe tend]] to be associated with the sign of impairment of judgment, apathy, and loss of the ability to regulate/modulate behavior.<ref>{{Cite journal |last1=Madhusoodanan |first1=Subramoniam |last2=Ting |first2=Mark Bryan |last3=Farah |first3=Tara |last4=Ugur |first4=Umran |date=2015-09-22 |title=Psychiatric aspects of brain tumors: A review |journal=World Journal of Psychiatry |volume=5 |issue=3 |pages=273–285 |doi=10.5498/wjp.v5.i3.273 |doi-access=free |issn=2220-3206 |pmc=4582304 |pmid=26425442}}</ref>

Findings have indicated abnormal functioning of [[brainstem]] structures in individuals with mental disorders such as [[schizophrenia]], and other disorders that have to do with impairments in maintaining sustained attention. Some abnormalities in the average size or shape of some regions of the brain have been found in some disorders, reflecting genes and experiences. Studies of schizophrenia have tended to find enlarged [[Ventricular system|ventricles]] and sometimes reduced volume of the [[cerebrum]] and [[hippocampus]], while studies of (psychotic) [[bipolar disorder]] have sometimes found increased [[amygdala]] volume. Findings differ over whether volumetric abnormalities are risk factors or are only found alongside the course of mental health problems, possibly reflecting neurocognitive or emotional stress processes and medication use or substance use. Some studies have also found reduced hippocampal volumes in [[major depression]], possibly worsening with time depression.{{cn|date=October 2024}}

[[File:Generic Neurotransmitter System.jpg|thumb|Generic Neurotransmitter System]]

===Neurotransmitter systems===
Abnormal levels of [[dopamine]] activity correspond with several disorders (reduced in [[ADHD]] and [[OCD]], and increased in schizophrenia). The dysfunction in [[serotonin]] and other [[monoamine]] neurotransmitters ([[norepinephrine]] and [[dopamine]]) correspond with certain mental disorders and their associated neural networks. Some include [[Major depressive disorder|major depression]], [[Obsessive compulsive disorder|obsessive-compulsive disorder]], [[phobias]], [[post-traumatic stress disorder]], and [[generalized anxiety disorder]]. Studies of depleted levels of [[monoamine]] neurotransmitters show an association with depression and other psychiatric disorders, but "... it should be questioned whether 5-HT [serotonin] represents just one of the final and not the main, factors in the neurological chain of events underlying psychopathological symptoms...."

Simplistic "chemical imbalance" explanations for mental disorders have never received empirical support; and most prominent psychiatrists, neuroscientists, and psychologists have not espoused such ill-defined, facile etiological theories. Instead, neurotransmitter systems have been understood in the context of the [[Diathesis–stress model|diathesis-stress]] or [[Biopsychosocial|biopsychosocial models]]. The following 1967 quote from renowned psychiatric and neuroscience researchers exemplifies this more sophisticated understanding (in contrast to the woolly "chemical imbalance" notion).

Whereas specific genetic factors may be of importance in the etiology of some, and possibly all, depressions, it is equally conceivable that early experiences of the infant or child may cause enduring biochemical changes, that may predispose some individuals to depressions in adulthood. It is not likely that changes in the metabolism of the biogenic amines alone will account for the complex phenomena of normal or pathological affect.

===Substance abuse===
{{no sources section|date=October 2024}}
Substance abuse, especially long-term abuse, can cause or exacerbate many mental disorders. [[Alcoholism]] is linked to [[Depression (mood)|depression]] while abuse of [[amphetamines]] and [[LSD]] can leave a person feeling [[paranoid]] and [[anxious]].

Correlations of mental disorders with drug use include [[Cannabis (drug)|cannabis]], alcohol, and [[caffeine]]. At more than 300&nbsp;mg, [[caffeine]] may cause [[anxiety]] or worsen anxiety disorders. Illicit drugs can stimulate particular parts of the brain that can affect development in adolescence. Cannabis has also been found to worsen depression and lessen an individual's [[motivation]]. Alcohol has the potential to damage "[[white matter]]" in the brain that affects [[thinking]] and [[memory]]. Alcohol is a problem in many countries due to many people participating in excessive drinking or [[binge drinking]].

==Environmental factors==
{{See also|Social determinants of health|Social determinants of health in poverty|Social determinants of mental health}}The term "environment" is very loosely defined in the context of mental illnesses. Unlike biological and psychological causes, environmental causes denote a wide range of [[Stressor|stressors]] that individuals experience in everyday life. They are more psychologically than biologically based.<ref>{{cite journal | vauthors = Schmidt CW | title = Environmental connections: a deeper look into mental illness | journal = Environmental Health Perspectives | volume = 115 | issue = 8 | pages = A404, A406-A404, A410 | date = August 2007 | pmid = 17687431 | pmc = 1940091 | doi = 10.1289/ehp.115-a404 }}</ref> Events that evoke feelings of loss are the most likely to cause a mental disorder to develop in an individual.<ref name=":1" /> 

Environmental factors include but are not limited to dysfunctional home life, poor [[Interpersonal relationship|interpersonal relationships]], [[substance abuse]], not meeting social expectations, low [[self-esteem]], and [[poverty]].<ref name=":1" /> The British charity organisation [[Mind (charity)|Mind]] lists [[Child abuse|childhood abuse]], [[Psychological trauma|trauma]], [[violence]], [[neglect]], [[social isolation]], [[discrimination]], [[grief]], stress, [[homelessness]], social disadvantage, debt, unemployment, caring for a family member or friend, and significant trauma as an adult (such as [[war]], an accident, or being the victim of a [[violent crime]]) as possible triggers of an episode of mental illness.<ref>{{Cite web |date=October 2017 |title=What causes mental health problems? |url=https://www.mind.org.uk/information-support/types-of-mental-health-problems/mental-health-problems-introduction/causes/ |website=mind.org.uk}}</ref>

Repeating generational patterns, behaviors that are passed down through different familial generations, are also a risk factor for mental illness, especially in children.<ref>{{Cite journal |last1=Landstedt |first1=Evelina |last2=Almquist |first2=Ylva B. |date=December 2019 |title=Intergenerational patterns of mental health problems: the role of childhood peer status position |journal=BMC Psychiatry |language=en |volume=19 |issue=1 |page=286 |doi=10.1186/s12888-019-2278-1 |issn=1471-244X |pmc=6749655 |pmid=31533680 |doi-access=free }}</ref>

===Life events and emotional stress===
Mistreatment in childhood or adulthood (including [[sexual abuse|sexual]]-, [[physical abuse|physical]]-, and [[emotional abuse]], [[domestic violence]], and [[bullying]]) has been linked to the onset of mental disorders through an interaction of societal, familial, psychological, and biological factors. More generally, negative or stressful life events have been implicated in the development of a range of disorders, including mood and anxiety disorders.<ref>{{Cite journal |last1=Phillips |first1=Anna C. |last2=Carroll |first2=Douglas |last3=Der |first3=Geoff |date=2015-07-04 |title=Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation |journal=Anxiety, Stress, & Coping |language=en |volume=28 |issue=4 |pages=357–371 |doi=10.1080/10615806.2015.1005078 |issn=1061-5806 |pmc=4772121 |pmid=25572915}}</ref><ref>{{Cite journal |last1=Hassanzadeh |first1=Akbar |last2=Heidari |first2=Zahra |last3=Feizi |first3=Awat |last4=Hassanzadeh Keshteli |first4=Ammar |last5=Roohafza |first5=Hamidreza |last6=Afshar |first6=Hamid |last7=Adibi |first7=Payman |date=2017 |title=Association of Stressful Life Events with Psychological Problems: A Large-Scale Community-Based Study Using Grouped Outcomes Latent Factor Regression with Latent Predictors |journal=Computational and Mathematical Methods in Medicine |language=en |volume=2017 |pages=1–12 |doi=10.1155/2017/3457103 |issn=1748-670X |pmc=5625761 |pmid=29312459 |doi-access=free }}</ref>

The main risks appear to be from the [[Cumulative effects (environment)|accumulation]] of such experiences over time, although a single major trauma can sometimes lead to disorders, especially [[post-traumatic stress disorder]]. [[Psychological resilience|Resilience]] to such experiences varies; a person may be resistant to some stressors but not to others. The psychological resilience of an individual can be affected by [[genetics]], temperamental characteristics, [[cognitive flexibility]], [[Coping|coping strategies]], and previous experiences.<ref>{{Cite journal |last1=Vella |first1=Shae-LeighCynthia |last2=Pai |first2=NageshB |date=2019 |title=A theoretical review of psychological resilience: Defining resilience and resilience research over the decades |journal=Archives of Medicine and Health Sciences |language=en |volume=7 |issue=2 |pages=233 |doi=10.4103/amhs.amhs_119_19 |s2cid=209406511 |issn=2321-4848 |doi-access=free }}</ref> For example, in the case of [[bipolar disorder]], stress is not a specific cause but does place genetically and biologically vulnerable people at risk for more severe forms of the illness.<ref>{{Cite journal |last1=Anderson |first1=Ian M. |last2=Haddad |first2=Peter M. |last3=Scott |first3=Jan |date=2012-12-27 |title=Bipolar disorder |url=https://www.bmj.com/content/345/bmj.e8508 |journal=BMJ |language=en |volume=345 |pages=e8508 |doi=10.1136/bmj.e8508 |issn=1756-1833 |pmid=23271744|s2cid=22156246 }}</ref><ref>{{Cite journal |last=Kerner |first=Berit |date=February 2014 |title=Genetics of bipolar disorder |journal=The Application of Clinical Genetics |volume=7 |language=en |pages=33–42 |doi=10.2147/TACG.S39297 |issn=1178-704X |pmc=3966627 |pmid=24683306 |doi-access=free }}</ref>

===Adverse childhood experiences===
{{main|Adverse childhood experiences}}
{{Further|Stress in early childhood|Childhood schizophrenia}}

The Adverse Childhood Experiences Study has shown a strong [[dose–response relationship]] between adverse childhood experiences or ACEs (such as physical and/or emotional neglect, [[Child abuse|abuse]], poverty, [[malnutrition]], and traumatic experiences) and numerous health, social, and behavioral problems including [[Suicide attempt|suicide attempts]] and the frequency of depressive episodes.<ref>{{Cite journal |last1=Felitti |first1=Vincent J |last2=Anda |first2=Robert F |last3=Nordenberg |first3=Dale |last4=Williamson |first4=David F |last5=Spitz |first5=Alison M |last6=Edwards |first6=Valerie |last7=Koss |first7=Mary P |last8=Marks |first8=James S |date=May 1998 |title=Relationship of Childhood Abuse and Household Dysfunction to Many of the Leading Causes of Death in Adults |journal=American Journal of Preventive Medicine |language=en |volume=14 |issue=4 |pages=245–258 |doi=10.1016/S0749-3797(98)00017-8|pmid=9635069 |s2cid=26055600 |doi-access=free }}</ref> Several such experiences can cause [[toxic stress]].<ref>{{Cite journal |last1=Bucci |first1=Monica |last2=Marques |first2=Sara Silvério |last3=Oh |first3=Debora |last4=Harris |first4=Nadine Burke |date=August 2016 |title=Toxic Stress in Children and Adolescents |url=https://doi.org/10.1016/j.yapd.2016.04.002 |journal=Advances in Pediatrics |volume=63 |issue=1 |pages=403–428 |doi=10.1016/j.yapd.2016.04.002 |pmid=27426909 |s2cid=37342598 |issn=0065-3101}}</ref>

ACEs may affect the structural and functional development of the brain and lead to abnormalities, and [[Chronic pain|chronic]] trauma can disrupt [[Immune response|immune responses]] and cause lasting dysregulated inflammatory response.<ref>{{Cite journal |last1=Crick |first1=Daisy C.P. |last2=Halligan |first2=Sarah L. |last3=Howe |first3=Laura D. |last4=Lacey |first4=Rebecca E. |last5=Khandaker |first5=Golam M. |last6=Burgner |first6=David |last7=Herbert |first7=Annie |last8=Suderman |first8=Matthew |last9=Anderson |first9=Emma L. |last10=Fraser |first10=Abigail |date=February 2022 |title=Associations between Adverse Childhood Experiences and the novel inflammatory marker glycoprotein acetyls in two generations of the Avon Longitudinal Study of Parents and Children birth cohort |journal=Brain, Behavior, and Immunity |language=en |volume=100 |pages=112–120 |doi=10.1016/j.bbi.2021.11.001 |pmc=8791601 |pmid=34793940}}</ref> A child's neurological development can be disrupted when chronically exposed to stressful events, and his/her cognitive functioning and/or ability to cope with negative emotions can diminish.<ref>{{Cite journal |last1=Morgan |first1=Cyleen A. |last2=Chang |first2=Yun-Hsuan |last3=Choy |first3=Olivia |last4=Tsai |first4=Meng-Che |last5=Hsieh |first5=Shulan |date=2021-12-31 |title=Adverse Childhood Experiences Are Associated with Reduced Psychological Resilience in Youth: A Systematic Review and Meta-Analysis |journal=Children |language=en |volume=9 |issue=1 |pages=27 |doi=10.3390/children9010027 |issn=2227-9067 |pmc=8773896 |pmid=35053652 |doi-access=free }}</ref> Over time, the child may adopt various harmful coping strategies that contribute to later mental and physical problems.<ref>{{Cite journal |last1=Sheffler |first1=Julia L. |last2=Piazza |first2=Jennifer R. |last3=Quinn |first3=Jamie M. |last4=Sachs-Ericsson |first4=Natalie J. |last5=Stanley |first5=Ian H. |date=2019-09-03 |title=Adverse childhood experiences and coping strategies: identifying pathways to resiliency in adulthood |journal=Anxiety, Stress, & Coping |language=en |volume=32 |issue=5 |pages=594–609 |doi=10.1080/10615806.2019.1638699 |issn=1061-5806 |pmc=6824267 |pmid=31288568}}</ref> Findings have been mixed, but some studies suggest that [[cognitive deficit]] is more related to neglect than other forms of adversity.<ref>{{Cite journal |last1=Gould |first1=Felicia |last2=Clarke |first2=Jennifer |last3=Heim |first3=Christine |last4=Harvey |first4=Philip D. |last5=Majer |first5=Matthias |last6=Nemeroff |first6=Charles B. |date=April 2012 |title=The effects of child abuse and neglect on cognitive functioning in adulthood |journal=Journal of Psychiatric Research |language=en |volume=46 |issue=4 |pages=500–506 |doi=10.1016/j.jpsychires.2012.01.005 |pmc=3307950 |pmid=22336639}}</ref><ref>{{Cite journal |last1=Berthelot |first1=Nicolas |last2=Paccalet |first2=Thomas |last3=Gilbert |first3=Elsa |last4=Moreau |first4=Isabel |last5=Mérette |first5=Chantal |last6=Gingras |first6=Nathalie |last7=Rouleau |first7=Nancie |last8=Maziade |first8=Michel |date=September 2015 |title=Childhood abuse and neglect may induce deficits in cognitive precursors of psychosis in high-risk children |journal=Journal of Psychiatry and Neuroscience |language=en |volume=40 |issue=5 |pages=336–343 |doi=10.1503/jpn.140211 |issn=1180-4882 |pmc=4543096 |pmid=26035064}}</ref>

Poor parenting is a risk factor for depression and anxiety. Separation, grief in families, and other forms childhood trauma are risk factors for [[schizophrenia]].<ref>{{Cite journal |last1=Popovic |first1=David |last2=Schmitt |first2=Andrea |last3=Kaurani |first3=Lalit |last4=Senner |first4=Fanny |last5=Papiol |first5=Sergi |last6=Malchow |first6=Berend |last7=Fischer |first7=Andre |last8=Schulze |first8=Thomas G. |last9=Koutsouleris |first9=Nikolaos |last10=Falkai |first10=Peter |date=2019-03-21 |title=Childhood Trauma in Schizophrenia: Current Findings and Research Perspectives |journal=Frontiers in Neuroscience |volume=13 |page=274 |doi=10.3389/fnins.2019.00274 |issn=1662-453X |pmc=6448042 |pmid=30983960 |doi-access=free }}</ref> Children are more susceptible to psychological harm from traumatic events than adults,<ref>{{Cite web |last=Peterson |first=Sarah |date=2018-02-01 |title=Effects |url=https://www.nctsn.org/what-is-child-trauma/trauma-types/early-childhood-trauma/effects |access-date=2023-07-02 |website=The National Child Traumatic Stress Network |language=en}}</ref> but their reaction does vary by individual child, age, the type of event, and the length of exposure.

[[Neglect]] is a form of mistreatment in which the responsible caretakers fail to provide the necessary age-appropriate care, supervision, and protection. It is different from [[abuse]] in that it is, in this context, not intentional in causing harms.<ref>{{Citation |last1=Gonzalez |first1=Dulce |title=Child Abuse and Neglect |date=2023 |url=http://www.ncbi.nlm.nih.gov/books/NBK459146/ |work=StatPearls |access-date=2023-07-02 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29083602 |last2=Bethencourt Mirabal |first2=Arian |last3=McCall |first3=Janelle D.}}</ref> The long-term effects of neglect can be reduced physical, emotional, and mental health throughout the victim's life.<ref>{{Citation |last1=Petersen |first1=Anne C. |title=Consequences of Child Abuse and Neglect |date=2014-03-25 |url=https://www.ncbi.nlm.nih.gov/books/NBK195987/ |work=New Directions in Child Abuse and Neglect Research |access-date=2023-07-02 |publisher=National Academies Press (US) |language=en |last2=Joseph |first2=Joshua |last3=Feit |first3=Monica }}</ref><ref>{{Citation |last=Horwath |first=Jan |title=Living with Child Neglect: The Impact on Children |date=2007 |url=http://dx.doi.org/10.1007/978-0-230-20982-4_3 |work=Child Neglect: Identification and Assessment |pages=41–68 |access-date=2023-07-02 |place=London |publisher=Macmillan Education UK |doi=10.1007/978-0-230-20982-4_3 |doi-broken-date=1 November 2024 |isbn=978-1-4039-3346-1}}</ref>

===Familial and close relationships===
Parental divorce, death, absence, or the lack of stability appears to increase the risk of mental disorders in a child.<ref>{{cite web | vauthors = Tashjian S, Mullins J |archive-url= https://web.archive.org/web/20181017014543/https://www.psychologyinaction.org/psychology-in-action-1/2018/4/23/k17ziyfqt1vy9tlytr9l9k48epdnur |   archive-date=October 17, 2018    |date=May 16, 2018|title=Parenting Styles and Child Behavior |url= https://www.psychologyinaction.org/psychology-in-action-1/2018/4/23/k17ziyfqt1vy9tlytr9l9k48epdnur |website=Psychology in Action}}</ref> Early social [[privation]], and the lack of "ongoing, harmonious, secure, committed" relationships have been implicated in the development of mental illnesses.<ref>{{cite web | url = https://www.mhanational.org/relationships | title = Relationships | work = Mental Health America | access-date = 8 August 2022 }}</ref> Continuous conflict with friends, one's support system, and family can all increase the risk of developing a mental illness or can worsen one's mental health.<ref>{{cite journal | vauthors = Marquis P | title = Family dysfunction as a risk factor in the development of antisocial behavior | journal = Psychological Reports | volume = 71 | issue = 2 | pages = 468–470 | date = October 1992 | pmid = 1410104 | doi = 10.2466/pr0.1992.71.2.468 | s2cid = 8826585 | doi-access = free }}</ref> 

[[Divorce]] is a factor that affects adults as well as children. Divorcees may have emotional adjustment problems due to a loss of intimacy and social connections; however, new statistics show that the negative effects of divorce have been overstated.<ref>{{cite journal | vauthors = Sander S, Strizzi JM, Øverup CS, Cipric A, Hald GM | title = When Love Hurts - Mental and Physical Health Among Recently Divorced Danes | journal = Frontiers in Psychology | volume = 11 | pages = 578083 | date = 2020-11-30 | pmid = 33329227 | pmc = 7734469 | doi = 10.3389/fpsyg.2020.578083 | doi-access = free }}</ref>

===Social expectations and self-esteem===
Having both too low or too high [[self-esteem]] can be detrimental to an individual's mental health.<ref>{{Cite journal |last1=Simpson |first1=J. |last2=Hillman |first2=R. |last3=Crawford |first3=T. |last4=Overton |first4=P. G. |date=2010-12-01 |title=Self-esteem and self-disgust both mediate the relationship between dysfunctional cognitions and depressive symptoms |url=https://doi.org/10.1007/s11031-010-9189-2 |journal=Motivation and Emotion |language=en |volume=34 |issue=4 |pages=399–406 |doi=10.1007/s11031-010-9189-2 |s2cid=145371730 |issn=1573-6644}}</ref><ref>{{Cite journal |last1=Baumeister |first1=Roy F. |last2=Smart |first2=Laura |last3=Boden |first3=Joseph M. |date=1996 |title=Relation of threatened egotism to violence and aggression: The dark side of high self-esteem. |url=http://doi.apa.org/getdoi.cfm?doi=10.1037/0033-295X.103.1.5 |journal=Psychological Review |language=en |volume=103 |issue=1 |pages=5–33 |doi=10.1037/0033-295X.103.1.5 |pmid=8650299 |issn=1939-1471}}</ref> Low self-esteem in particular can result in aggression, self-deprecating behavior, anxiety, and other mental disorders.<ref>{{Cite journal |last1=Sowislo |first1=Julia Friederike |last2=Orth |first2=Ulrich |date=January 2013 |title=Does low self-esteem predict depression and anxiety? A meta-analysis of longitudinal studies. |url=http://doi.apa.org/getdoi.cfm?doi=10.1037/a0028931 |journal=Psychological Bulletin |language=en |volume=139 |issue=1 |pages=213–240 |doi=10.1037/a0028931 |pmid=22730921 |issn=1939-1455}}</ref> Being perceived as someone who does not "fit in" can result in bullying and other types of emotional abuse,<ref>{{Cite journal |last1=Hoover |first1=John H. |last2=Oliver |first2=Ronald L. |last3=Thomson |first3=Keith A. |date=December 1993 |title=Perceived Victimization by School Bullies: New Research and Future Direction |url=https://onlinelibrary.wiley.com/doi/10.1002/j.2164-4683.1993.tb00133.x |journal=The Journal of Humanistic Education and Development |language=en |volume=32 |issue=2 |pages=76–84 |doi=10.1002/j.2164-4683.1993.tb00133.x}}</ref><ref>{{Cite journal |last1=Nansel |first1=Tonja R. |last2=Overpeck |first2=Mary |last3=Pilla |first3=Ramani S. |last4=Ruan |first4=W. June |last5=Simons-Morton |first5=Bruce |last6=Scheidt |first6=Peter |date=2001-04-25 |title=Bullying Behaviors Among US Youth: Prevalence and Association With Psychosocial Adjustment |journal=JAMA |language=en |volume=285 |issue=16 |pages=2094–2100 |doi=10.1001/jama.285.16.2094 |issn=0098-7484 |pmc=2435211 |pmid=11311098}}</ref> which can lead to the victim experiencing depression, anger, and loneliness.<ref>{{Citation |last1=Rivara |first1=Frederick |title=Consequences of Bullying Behavior |date=2016-09-14 |url=https://www.ncbi.nlm.nih.gov/books/NBK390414/ |work=Preventing Bullying Through Science, Policy, and Practice |access-date=2023-07-02 |publisher=National Academies Press (US) |language=en |last2=Menestrel |first2=Suzanne Le |last3=Prevention |first3=Committee on the Biological and Psychosocial Effects of Peer Victimization: Lessons for Bullying |last4=Board on Children |first4=Youth |last5=Justice |first5=Committee on Law and |last6=Education |first6=Division of Behavioral and Social Sciences and |last7=Division |first7=Health and Medicine |last8=National Academies of Sciences |first8=Engineering}}</ref>

===Poverty===
{{See|Socioeconomic status and mental health|Social determinants of mental health}}
[[File:National Geographic, v31, Czech poor peasant children.jpg|thumb|Poor Czech poor children in 1917.]]
Studies show that there is a [[Correlation|direct correlation]] between [[poverty]] and mental illness: the lower the socioeconomic status of an individual, the higher the risk of mental illness. Impoverished people in England, defined as those who live in the lowest 20% income bracket, are two to three times more likely to develop mental illness than those of a higher [[Social class|economic class]].<ref>Marmot MG. ''Fair Society  Healthy Lives : The Marmot Review ; Strategic Review of Health Inequalities in England Post-2010''. London: Marmot Review; 2010.</ref> This increased risk remains consistent for all poor individuals regardless of any in-group demographic differences, as all disadvantaged families experience economic stressors such as unemployment or lack of housing. A lower or more insecure educational, occupational, economic, or social position is generally linked to more mental disorders.<ref>{{Cite journal |last=Perry |first=Melissa J. |date=1996-09-01 |title=The relationship between social class and mental disorder |url=https://doi.org/10.1007/BF02262736 |journal=Journal of Primary Prevention |language=en |volume=17 |issue=1 |pages=17–30 |doi=10.1007/BF02262736 |pmid=24254919 |s2cid=144679736 |issn=1573-6547}}</ref> Children from these backgrounds may have low levels of self-efficiency and self-worth.<ref>{{Cite journal |last1=Doi |first1=Satomi |last2=Fujiwara |first2=Takeo |last3=Isumi |first3=Aya |last4=Ochi |first4=Manami |date=2019 |title=Pathway of the Association Between Child Poverty and Low Self-Esteem: Results From a Population-Based Study of Adolescents in Japan |journal=Frontiers in Psychology |volume=10 |page=937 |doi=10.3389/fpsyg.2019.00937 |issn=1664-1078 |pmc=6511812 |pmid=31133920 |doi-access=free }}</ref> Studies have also shown a strong relationship between poverty and [[substance abuse]], another risk factor in the onset of mental disorders.<ref>{{Cite journal |last1=Manhica |first1=Hélio |last2=Straatmann |first2=Viviane S. |last3=Lundin |first3=Andreas |last4=Agardh |first4=Emilie |last5=Danielsson |first5=Anna-Karin |date=July 2021 |title=Association between poverty exposure during childhood and adolescence, and drug use disorders and drug-related crimes later in life |journal=Addiction |language=en |volume=116 |issue=7 |pages=1747–1756 |doi=10.1111/add.15336 |issn=0965-2140 |pmc=8247994 |pmid=33197093}}</ref>

Problems in one's community or culture including poverty, unemployment or [[underemployment]], a lack of [[Group cohesiveness|social cohesion]], and migration have been associated with the development of mental disorders.<ref>{{Cite journal |last1=Breedvelt |first1=Josefien J. F. |last2=Tiemeier |first2=Henning |last3=Sharples |first3=Evelyn |last4=Galea |first4=Sandro |last5=Niedzwiedz |first5=Claire |last6=Elliott |first6=Iris |last7=Bockting |first7=Claudi L. |date=July 2022 |title=The effects of neighbourhood social cohesion on preventing depression and anxiety among adolescents and young adults: rapid review |journal=BJPsych Open |language=en |volume=8 |issue=4 |pages=e97 |doi=10.1192/bjo.2022.57 |issn=2056-4724 |pmc=9230698 |pmid=35642359}}</ref> Personal resources, community factors, and interactions between individual and regional-level income levels have been implicated.<ref>{{Cite journal |last1=Sareen |first1=Jitender |last2=Afifi |first2=Tracie O. |last3=McMillan |first3=Katherine A. |last4=Asmundson |first4=Gordon J. G. |date=2011-04-01 |title=Relationship Between Household Income and Mental Disorders: Findings From a Population-Based Longitudinal Study |url=http://archpsyc.jamanetwork.com/article.aspx?doi=10.1001/archgenpsychiatry.2011.15 |journal=Archives of General Psychiatry |language=en |volume=68 |issue=4 |pages=419–427 |doi=10.1001/archgenpsychiatry.2011.15 |pmid=21464366 |s2cid=39076836 |issn=0003-990X}}</ref> Socioeconomic deprivation in neighborhoods can cause worsen mental health, even after accounting for genetic factors.<ref>{{Cite journal |last1=Raphael |first1=Eva |last2=White |first2=Justin S. |last3=Li |first3=Xinjun |last4=Cederin |first4=Klas |last5=Glymour |first5=M. Maria |last6=Sundquist |first6=Kristina |last7=Sundquist |first7=Jan |last8=Hamad |first8=Rita |date=May 2020 |title=Neighborhood Deprivation and Mental Health Among Immigrants to Sweden |journal=Epidemiology |language=en |volume=31 |issue=3 |pages=e25–e27 |doi=10.1097/EDE.0000000000001160 |issn=1044-3983 |pmc=7138696 |pmid=31977591}}</ref> According to a 2009 meta-analysis by Paul and Moser, countries with high income inequality and poor unemployment protections have worse mental health outcomes among the unemployed.<ref>{{Cite web |title=The toll of job loss |url=https://www.apa.org/monitor/2020/10/toll-job-loss |access-date=2023-11-26 |website=www.apa.org}}</ref>

The effects of different socioeconomic factors varies by country.<ref>{{Cite journal |last1=Currie |first1=Janet |last2=Stabile |first2=Mark |date=2003-11-01 |title=Socioeconomic Status and Child Health: Why Is the Relationship Stronger for Older Children? |url=https://pubs.aeaweb.org/doi/10.1257/000282803322655563 |journal=American Economic Review |language=en |volume=93 |issue=5 |pages=1813–1823 |doi=10.1257/000282803322655563 |pmid=29058847 |issn=0002-8282}}</ref><ref>{{Cite journal |last1=Cameron |first1=Lisa |last2=Williams |first2=Jenny |date=2009-05-01 |title=Is the relationship between socioeconomic status and health stronger for older children in developing countries? |url=https://read.dukeupress.edu/demography/article/46/2/303/169929/Is-the-relationship-between-socioeconomic-status |journal=Demography |language=en |volume=46 |issue=2 |pages=303–324 |doi=10.1353/dem.0.0054 |issn=0070-3370 |pmc=2831276 |pmid=21305395}}</ref> Minority [[ethnic]] groups, including first or second-generation [[immigrants]], are at a greater risk of developing mental disorders. This has been attributed to the insecurities in their lives and their disadvantages, including [[racism]].<ref>{{Cite journal |last1=Kirmayer |first1=L. J. |last2=Narasiah |first2=L. |last3=Munoz |first3=M. |last4=Rashid |first4=M. |last5=Ryder |first5=A. G. |last6=Guzder |first6=J. |last7=Hassan |first7=G. |last8=Rousseau |first8=C. |last9=Pottie |first9=K. |last10=for the Canadian Collaboration for Immigrant and Refugee Health (CCIRH) |date=2011-09-06 |title=Common mental health problems in immigrants and refugees: general approach in primary care |journal=Canadian Medical Association Journal |language=en |volume=183 |issue=12 |pages=E959–E967 |doi=10.1503/cmaj.090292 |issn=0820-3946 |pmc=3168672 |pmid=20603342}}</ref> There have been alternate models, such as the [[drift hypothesis]] to account for the complex relationship between an individual's social status and mental health.<ref>{{Cite journal |last=Fox |first=John W. |date=December 1990 |title=Social Class, Mental Illness, and Social Mobility: The Social Selection-Drift Hypothesis for Serious Mental Illness |url=http://dx.doi.org/10.2307/2136818 |journal=Journal of Health and Social Behavior |volume=31 |issue=4 |pages=344–353 |doi=10.2307/2136818 |jstor=2136818 |pmid=2135936 |issn=0022-1465}}</ref>

==Psychological and individual factors, including resilience==
Some clinicians believe that psychological characteristics alone determine mental disorders. Others speculate that abnormal behavior can be explained by a mix of social and psychological factors. In many examples, environmental and psychological triggers complement one another resulting in emotional stress, which in turn activates a mental illness. Each person is unique in how they will react to psychological stressors. What may break one person may have little to no effect on another. Psychological stressors, which can trigger mental illness, are as follows: emotional, physical, or sexual abuse, loss of a significant loved one, neglect, and being unable to relate to others.<ref>{{cite journal | vauthors = Schneiderman N, Ironson G, Siegel SD | title = Stress and health: psychological, behavioral, and biological determinants | journal = Annual Review of Clinical Psychology | volume = 1 | pages = 607–628 | date = 2005 | pmid = 17716101 | pmc = 2568977 | doi = 10.1146/annurev.clinpsy.1.102803.144141 }}</ref>

The inability to relate to others is also known as [[emotional detachment]]. Emotional detachment makes it difficult for an individual to empathize with others or to share their feelings. These individuals tend to stress the importance of their independence and tend to struggle relating to others. An emotionally detached person may try to rationalize or apply logic to a situation to which there is no logical explanation. Often, the inability to relate to others stems from a traumatic event.{{cn|date=October 2024}}

Mental characteristics of individuals, as assessed by both neurological and psychological studies, have been linked to the development and maintenance of mental disorders. This includes cognitive or [[neurocognitive]] factors, such as the way a person perceives, thinks, or feels about certain things; or an individual's overall personality, [[temperament]], or [[Coping|coping style]] or the extent of protective factors or "positive illusions" such as optimism, personal control and a sense of meaning.{{cn|date=October 2024}}

== See also ==
* [[Air pollution]]
* [[Correlates of crime]]
* [[Diseases of poverty]]
* [[Social medicine]]
* [[Winner and loser culture]]

== References ==
{{Reflist}}

[[Category:Causes of mental disorders| ]]
[[Category:Biology of bipolar disorder]]
[[Category:Cause (medicine)|Mental disorders]]
[[Category:Biology of attention deficit hyperactivity disorder]]
[[Category:Biology of obsessive–compulsive disorder]]