Editing Seasonal affective disorder

{{Use mdy dates|date=March 2013}}
{{Infobox medical condition (new)
| name            = Seasonal affective disorder
| synonyms        = Seasonal mood disorder, depressive disorder with seasonal pattern, winter depression, winter blues, January blues, summer depression, seasonal depression
| image           = File:Light Therapy for SAD.jpg
| caption         = Bright [[light therapy]] is a common treatment for seasonal affective disorder and for [[circadian rhythm sleep disorder]]s.
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| field           = [[Psychiatry]] 
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<!-- Definition and symptoms -->

'''Seasonal affective disorder''' ('''SAD''') is a [[mood disorder]] subset in which people who typically have normal [[mental health]] throughout most of the year exhibit [[depression (mood)|depressive]] symptoms at the same time each year.<ref name="Oginska, Halszka 2014">{{cite journal | vauthors = Oginska H, Oginska-Bruchal K | title = Chronotype and personality factors of predisposition to seasonal affective disorder | journal = Chronobiology International | volume = 31 | issue = 4 | pages = 523–31 | date = May 2014 | pmid = 24397301 | doi = 10.3109/07420528.2013.874355 | s2cid = 22428871 }}</ref><ref>Ivry, Sara (August 13, 2002). [https://query.nytimes.com/gst/fullpage.html?res=9C03E4DA103AF930A2575BC0A9649C8B63&sec=health Seasonal Depression can Accompany Summer Sun]. ''The New York Times''. Retrieved September 6, 2008</ref> It is commonly, but not always, associated with the reductions or increases in total daily sunlight hours that occur during the [[winter]] or [[summer]].

Common symptoms include sleeping too much, having little to no energy, and overeating.<ref>{{MedlinePlusOverview|seasonalaffectivedisorder}}</ref> The condition in the summer can include heightened [[anxiety]].<ref name="mayoclinic.com">[http://www.mayoclinic.com/health/seasonal-affective-disorder/DS00195/DSECTION=2 Seasonal affective disorder (SAD): Symptoms]. MayoClinic.com (September 22, 2011). Retrieved on March 24, 2013.</ref> However, there are significant differences in the duration, severity, and symptoms of each individual's experience of SAD. For instance, in a fifth of patients, the disorder completely resolves in five to eleven years, whereas for 33-44% of patients, it progresses into non-seasonal major depression.<ref>{{Cite journal |last1=Nussbaumer-Streit |first1=Barbara |last2=Pjrek |first2=Edda |last3=Kien |first3=Christina |last4=Gartlehner |first4=Gerald |last5=Bartova |first5=Lucie |last6=Friedrich |first6=Michaela-Elena |last7=Kasper |first7=Siegfried |last8=Winkler |first8=Dietmar |date=2018-11-26 |title=Implementing prevention of seasonal affective disorder from patients' and physicians' perspectives – a qualitative study |journal=BMC Psychiatry |volume=18 |issue=1 |pages=372 |doi=10.1186/s12888-018-1951-0 |doi-access=free |issn=1471-244X |pmc=6260561 |pmid=30477472}}</ref>

<!-- Diagnosis -->
In the [[Diagnostic and Statistical Manual of Mental Disorders|DSM-IV]] and [[DSM-5]], its status as a standalone condition was changed: It is no longer classified as a unique mood disorder but is now a specifier (called "with [[Seasonality|seasonal pattern]]") for recurrent [[major depressive disorder]] that occurs at a specific time of the year and fully remits otherwise.<ref name="DSM-5-Bipolar and related disorders">{{Cite book| last=American Psychiatric Association| year=2013| title=Diagnostic and Statistical Manual of Mental Disorders| edition=Fifth| publisher=American Psychiatric Publishing| location=Arlington, VA| pages=[https://archive.org/details/diagnosticstatis0005unse/page/123 123–154]| isbn=978-0-89042-555-8| url=https://archive.org/details/diagnosticstatis0005unse/page/123}}</ref> Although experts were initially skeptical, the condition eventually became recognized as a common disorder.<ref>Friedman, Richard A. (December 18, 2007) [https://www.nytimes.com/2007/12/18/health/18mind.html Brought on by Darkness, Disorder Needs Light]. ''[[New York Times]]''.</ref>{{Additional citation needed|date=April 2025}} However, the validity of SAD was called into question by a 2016 analysis from the [[Center for Disease Control|Centers for Disease Control]], when it found no links between depression, seasonality or sunlight exposure.<ref name="Traffanstedt et al., 2016">{{cite journal |vauthors= Traffanstedt M, Mehta S, LoBello S|date=2016 |title= Major Depression With Seasonal Variation: Is It a Valid Construct? |url=http://journals.sagepub.com/doi/abs/10.1177/2167702615615867 |journal=Clinical Psychological Science |volume=4 |issue=5 |pages=825–834 |doi=10.1177/2167702615615867|s2cid=43574728 }}</ref><!-- Epidemiology and history -->

In the United States, the percentage of the population affected by SAD ranges from 1.4% of the population in [[Florida]] to 9.9% in [[Alaska]].<ref>{{cite book| vauthors = Nolen-Hoeksema S |title=Abnormal Psychology|date=2014|publisher=McGraw-Hill Education|location=New York, New York|isbn=978-1-259-06072-4|pages=179|edition=6th}}</ref> 

==Signs and symptoms==
[[File:Seasonal affective disorder (Depressive Disorder with Seasonal Pattern).webm|thumb|upright=1.3|Video explanation]]SAD is a type of [[major depressive disorder]], and those with the condition may exhibit any of the associated symptoms, such as feelings of hopelessness and worthlessness, thoughts of suicide, loss of interest in activities, withdrawal from social interaction, sleep and appetite problems, difficulty with concentrating and making decisions, decreased libido, a lack of energy, or agitation.<ref name="mayoclinic.com"/> Symptoms of winter SAD often include falling asleep earlier or in less than 5 minutes in the evening, oversleeping or difficulty waking up in the morning, nausea, and a tendency to overeat, often with a craving for carbohydrates, which leads to weight gain.<ref>{{cite journal | vauthors = Partonen T, Lönnqvist J | title = Seasonal affective disorder | journal = Lancet | volume = 352 | issue = 9137 | pages = 1369–74 | date = October 1998 | pmid = 9802288 | doi = 10.1016/s0140-6736(98)01015-0 | s2cid = 42760726 }}</ref> SAD is typically associated with winter depression, but [[springtime lethargy]] or other seasonal mood patterns are not uncommon.<ref>{{cite web|title=What is SAD (Seasonal Affective Disorder)?|url=http://sadlampsusa.com/articles/what-is-sad/|access-date=21 February 2018}}</ref> Although each individual case is different, in contrast to winter SAD, people who experience spring and summer depression may be more likely to show symptoms such as insomnia, decreased appetite and weight loss, and agitation or anxiety.<ref name="mayoclinic.com"/>

===Bipolar disorder===
''With seasonal pattern'' is a specifier for ''bipolar and related disorders'', including bipolar I disorder and bipolar II disorder.<ref name="DSM-5-Bipolar and related disorders"/>
Most people with SAD experience [[major depressive disorder]], but as many as 20% may have a [[bipolar disorder]]. Bipolar disorder is characterized by alternating episodes of depression and mania or hypomania. Depressive episodes include symptoms such as low energy, difficulty concentrating, changes in sleep and appetite, feelings of hopelessness, and suicidal thoughts. Manic episodes, which are more common in bipolar I disorder, may include elevated mood, decreased need for sleep, impulsivity, and increased activity or risky behaviors. In contrast, hypomania (seen in bipolar II disorder) presents as a milder form of mania without significant impairment in daily life. <ref>{{Cite web |title=Bipolar Disorders |url=https://www.psychiatry.org/Patients-Families/Bipolar-Disorders |access-date=2025-04-03 |website=www.psychiatry.org |language=en}}</ref> It is important to distinguish between diagnoses because there are important treatment differences.<ref>{{cite web |url= http://www.mooddisorderscanada.ca/documents/Consumer%20and%20Family%20Support/Depression.pdf |title= Depression |access-date= August 8, 2009 |publisher= Mood Disorders Society of Canada |archive-date= July 6, 2011 |archive-url= https://web.archive.org/web/20110706185913/http://www.mooddisorderscanada.ca/documents/Consumer%20and%20Family%20Support/Depression.pdf |url-status= dead }}</ref> In these cases, people who have the ''With seasonal pattern'' specifier may experience a depressive episode either due to major depressive disorder or as part of bipolar disorder during the winter and remit in the summer.<ref name="DSM-5-Bipolar and related disorders"/> Around 25% of patients with [[bipolar disorder]] may present with a depressive seasonal pattern, which is associated with bipolar II disorder, rapid cycling, eating disorders, and more depressive episodes.<ref name="Geoffroy-2013">{{cite journal | vauthors = Geoffroy PA, Bellivier F, Scott J, Boudebesse C, Lajnef M, Gard S, Kahn JP, Azorin JM, Henry C, Leboyer M, Etain B | title = Bipolar disorder with seasonal pattern: clinical characteristics and gender influences | journal = Chronobiology International | volume = 30 | issue = 9 | pages = 1101–7 | date = November 2013 | pmid = 23931033 | pmc = 5225270 | doi = 10.3109/07420528.2013.800091 }}</ref> Differences in biological sex display distinct clinical characteristics associated to seasonal pattern: males present with more Bipolar II disorder and a higher number of depressive episodes, and females with rapid cycling and eating disorders.<ref name="Geoffroy-2013"/>

=== ADHD ===
A study by the [[National Institutes of Health|National Institute of Health]] published findings in 2016 that concluded, "seasonal and circadian rhythm disturbances are significantly associated with [[Attention deficit hyperactivity disorder|ADHD]] symptoms." Participants in the study who had ADHD were three times more likely to have SAD symptoms (9.9% vs 3.3%), and about 2.7 times more likely to have s-SAD symptoms (12.5% vs 4.6%).<ref>{{Cite journal |last1=Wynchank |first1=Dora S. |last2=Bijlenga |first2=Denise |last3=Lamers |first3=Femke |last4=Bron |first4=Tannetje I. |last5=Winthorst |first5=Wim H. |last6=Vogel |first6=Suzan W. |last7=Penninx |first7=Brenda W. |last8=Beekman |first8=Aartjan T. |last9=Kooij |first9=J. Sandra |date=2016-10-10 |title=ADHD, circadian rhythms and seasonality |url=https://pubmed.ncbi.nlm.nih.gov/27423070/ |journal=Journal of Psychiatric Research |volume=81 |pages=87–94 |doi=10.1016/j.jpsychires.2016.06.018 |issn=1879-1379 |pmid=27423070}}</ref> Those with ADHD and SAD are likely to experience sluggishness, irritability, and withdrawal.<ref>{{Cite web |last=Team |first=ADDA Editorial |date=2023-11-30 |title=Beat the Blues! Tips for ADHD and Seasonal Affective Disorder |url=https://add.org/beat-the-blues-how-adults-with-adhd-can-recognize-and-treat-seasonal-affective-disorder-sad/?gad_source=1&gclid=cj0kcqjwhmq-bhcfarisagvo0kdaf8ftakgrffqqm0pkibofckczyhgycd9vxpp1qaigqlkkvyoqdaaaahhlealw_wcb |access-date=2025-03-13 |website=ADDA - Attention Deficit Disorder Association |language=en-US}}</ref> A study published in the ''Journal of Affective Disorders'' found that approximately 27% of adults with ADHD also experience SAD, with women being more susceptible than men. <ref>{{Cite journal |date=2024-12-23 |title=Seasonal Affective Disorder (SAD): Background, Pathophysiology, Epidemiology |url=https://emedicine.medscape.com/article/2500054-overview?utm_source=chatgpt.com&form=fpf}}</ref>  

==Cause==
In many species, activity is diminished during the winter months, in response to the reduction in available food, the reduction of [[sunlight]] (especially for [[diurnality|diurnal]] animals), and the difficulties of surviving in cold weather. [[Hibernation]] is an extreme example, but even species that do not hibernate often exhibit changes in behavior during the winter.<ref name="Nesse">{{Cite book| vauthors = Nesse RM, Williams GC |author-link1= Randolph M. Nesse |author-link2= George C. Williams (biologist)|title= Why We Get Sick|edition= First|publisher= Vintage Books|location= New York|isbn= 978-0812922240|year= 1996|url= https://archive.org/details/whywegetsicknew00ness}}</ref>

Various proximate causes have been proposed. One possibility is that SAD is related to a lack of [[serotonin]], and [[serotonin polymorphism]]s could play a role in SAD,<ref>{{cite journal | vauthors = Johansson C, Smedh C, Partonen T, Pekkarinen P, Paunio T, Ekholm J, Peltonen L, Lichtermann D, Palmgren J, Adolfsson R, Schalling M | title = Seasonal affective disorder and serotonin-related polymorphisms | journal = Neurobiology of Disease | volume = 8 | issue = 2 | pages = 351–7 | date = April 2001 | pmid = 11300730 | doi = 10.1006/nbdi.2000.0373 | s2cid = 10841651 }}</ref> although this has been disputed.<ref>{{cite journal | vauthors = Johansson C, Willeit M, Levitan R, Partonen T, Smedh C, Del Favero J, Bel Kacem S, Praschak-Rieder N, Neumeister A, Masellis M, Basile V, Zill P, Bondy B, Paunio T, Kasper S, Van Broeckhoven C, Nilsson LG, Lam R, Schalling M, Adolfsson R | title = The serotonin transporter promoter repeat length polymorphism, seasonal affective disorder and seasonality | journal = Psychological Medicine | volume = 33 | issue = 5 | pages = 785–92 | date = July 2003 | pmid = 12877393 | doi = 10.1017/S0033291703007372 | s2cid = 45837170 }}</ref> Mice incapable of turning serotonin into N-acetylserotonin (by [[serotonin N-acetyltransferase]]) appear to express "depression-like" behavior, and [[antidepressant]]s such as [[fluoxetine]] increase the amount of the enzyme serotonin N-acetyltransferase, resulting in an antidepressant-like effect.<ref>{{cite journal | vauthors = Uz T, Manev H | title = Prolonged swim-test immobility of serotonin N-acetyltransferase (AANAT)-mutant mice | journal = Journal of Pineal Research | volume = 30 | issue = 3 | pages = 166–70 | date = April 2001 | pmid = 11316327 | doi = 10.1034/j.1600-079X.2001.300305.x | s2cid = 24360614 }}</ref> Another theory is that the cause may be related to [[melatonin]], which is produced in dim light and darkness by the [[pineal gland]],<ref name="search.proquest" /> since there are direct connections, via the [[retinohypothalamic tract]] and the [[suprachiasmatic nucleus]], between the retina and the pineal gland.<ref>{{Citation |last1=Arendt |first1=Josephine |title=Physiology of the Pineal Gland and Melatonin |date=2000 |work=Endotext |editor-last=Feingold |editor-first=Kenneth R. |url=https://www.ncbi.nlm.nih.gov/books/NBK550972/ |access-date=2025-03-13 |place=South Dartmouth (MA) |publisher=MDText.com, Inc. |pmid=31841296 |last2=Aulinas |first2=Anna |editor2-last=Anawalt |editor2-first=Bradley |editor3-last=Blackman |editor3-first=Marc R. |editor4-last=Boyce |editor4-first=Alison}}</ref>{{Citation needed|date=November 2012}} Melatonin secretion is controlled by the [[Endogeny (biology)|endogenous]] [[circadian clock]], but can also be suppressed by bright light.<ref name="search.proquest" />

One study looked at whether some people could be predisposed to SAD based on personality traits. Correlations between certain personality traits such as higher levels of [[neuroticism]], agreeableness, openness, and an avoidance-oriented coping style, appeared to be common in those with SAD.<ref name="Oginska, Halszka 2014"/>

Per Pfizer, risk factors for SAD include being a female, younger age, previously being diagnosed with extreme depression or bipolar disorder, having a family history of the same disease, or living a considerable distance from the equator.<ref>{{Cite web |title=Shedding Light on Seasonal Affective Disorder {{!}} Pfizer |url=https://www.pfizer.com/news/articles/shedding_light_on_seasonal_affective_disorder |access-date=2025-03-13 |website=www.pfizer.com |language=en}}</ref> 

==Pathophysiology==
Seasonal mood variations are believed to be related to light. An argument for this view is the effectiveness of bright-[[light therapy]].<ref name = "Lam">{{cite journal | vauthors = Lam RW, Levitt AJ, Levitan RD, Enns MW, Morehouse R, Michalak EE, Tam EM | title = The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder | journal = The American Journal of Psychiatry | volume = 163 | issue = 5 | pages = 805–12 | date = May 2006 | pmid = 16648320 | doi = 10.1176/appi.ajp.163.5.805 }}</ref> SAD is measurably present at latitudes in the [[Arctic Circle|Arctic region]], such as northern [[Finland]] (around [[64 degrees north]] latitude), where the rate of SAD is 9.5%.<ref name = "Avery">{{cite journal | vauthors = Avery DH, Eder DN, Bolte MA, Hellekson CJ, Dunner DL, Vitiello MV, Prinz PN | title = Dawn simulation and bright light in the treatment of SAD: a controlled study | journal = Biological Psychiatry | volume = 50 | issue = 3 | pages = 205–16 | date = August 2001 | pmid = 11513820 | doi = 10.1016/S0006-3223(01)01200-8 | s2cid = 21123296 }}</ref> Cloud cover may contribute to the negative effects of SAD.<ref name = "Modell">{{cite journal | vauthors = Modell JG, Rosenthal NE, Harriett AE, Krishen A, Asgharian A, Foster VJ, Metz A, Rockett CB, Wightman DS | title = Seasonal affective disorder and its prevention by anticipatory treatment with bupropion XL | journal = Biological Psychiatry | volume = 58 | issue = 8 | pages = 658–67 | date = October 2005 | pmid = 16271314 | doi = 10.1016/j.biopsych.2005.07.021 | s2cid = 25662514 }}</ref> There is evidence that many patients with SAD have [[Delayed sleep phase disorder|a delay]] in their [[circadian rhythm]], and that bright light treatment corrects these delays which may be responsible for the improvement in patients.<ref name="search.proquest">{{cite journal | vauthors = Lam RW, Levitan RD | title = Pathophysiology of seasonal affective disorder: a review | journal = Journal of Psychiatry & Neuroscience | volume = 25 | issue = 5 | pages = 469–80 | date = November 2000 | pmid = 11109298 | pmc = 1408021 }}</ref>

The symptoms of it mimic those of [[Dysthymia]] or even [[major depressive disorder]]. There is also potential risk of suicide in some patients experiencing SAD. One study reports 6–35% of people with the condition required hospitalization during one period of illness.<ref name = "Modell"/> At times, patients may not feel depressed, but rather lack energy to perform everyday activities.<ref name = "Lam"/>

Subsyndromal Seasonal Affective Disorder (s-SAD or SSAD) is a milder form of SAD experienced by an estimated 14.3% (vs. 6.1% SAD) of the U.S. population.<ref name = "Avery2">{{cite journal | vauthors = Avery DH, Kizer D, Bolte MA, Hellekson C | title = Bright light therapy of subsyndromal seasonal affective disorder in the workplace: morning vs. afternoon exposure | journal = Acta Psychiatrica Scandinavica | volume = 103 | issue = 4 | pages = 267–74 | date = April 2001 | pmid = 11328240 | doi = 10.1034/j.1600-0447.2001.00078.x | s2cid = 1342943 }}</ref> The blue feeling experienced by both those with SAD and with SSAD can usually be dampened or extinguished by exercise and increased outdoor activity, particularly on sunny days, resulting in increased solar exposure.<ref name = "Leppämäki">{{cite journal | vauthors = Leppämäki S, Haukka J, Lönnqvist J, Partonen T | title = Drop-out and mood improvement: a randomised controlled trial with light exposure and physical exercise [ISRCTN36478292] | journal = BMC Psychiatry | volume = 4 | pages = 22 | date = August 2004 | pmid = 15306031 | pmc = 514552 | doi = 10.1186/1471-244X-4-22 | doi-access = free }}</ref> Connections between human mood, as well as energy levels, and the seasons are well documented, even in healthy individuals.<ref>{{cite journal | vauthors = Partonen T, Lönnqvist J | title = Bright light improves vitality and alleviates distress in healthy people | journal = Journal of Affective Disorders | volume = 57 | issue = 1–3 | pages = 55–61 | date = 2000 | pmid = 10708816 | doi = 10.1016/S0165-0327(99)00063-4 }}</ref>

==Diagnosis==
According to the American Psychiatric Association [[DSM-IV]] criteria,<ref>{{Cite book| vauthors = Gabbard GO |title=Treatment of Psychiatric Disorders |edition=3rd |volume=2 |publisher= American Psychiatric Publishing |location= Washington, DC |page= 1296 }}</ref> Seasonal Affective Disorder is not regarded as a separate disorder. It is called a "course specifier" and may be applied as an added description to the pattern of [[major depressive episode]]s in patients with [[major depressive disorder]] or patients with [[bipolar disorder]].

The "Seasonal Pattern Specifier" must meet four criteria: depressive episodes at a particular time of the year; remissions or mania/hypomania at a characteristic time of year; these patterns must have lasted two years with no nonseasonal major depressive episodes during that same period; and these seasonal depressive episodes outnumber other depressive episodes throughout the patient's lifetime. The [[Mayo Clinic]] describes three types of SAD, each with its own set of symptoms.<ref name="mayoclinic.com"/>

==Management==
{{See also|Occupational therapy in the management of seasonal affective disorder}}
Treatments for classic (winter-based) seasonal affective disorder include [[light therapy]], medication, [[Negative air ionization therapy|ionized-air administration]],<ref name="Terman" /> [[cognitive-behavioral therapy]], and carefully timed supplementation<ref name="ohsu.edu">{{cite journal | vauthors = Bhattacharjee Y | title = Psychiatric research. Is internal timing key to mental health? | journal = Science | volume = 317 | issue = 5844 | pages = 1488–90 | date = September 2007 | pmid = 17872420 | doi = 10.1126/science.317.5844.1488 | s2cid = 71387673 }}</ref> of the hormone [[melatonin]].<ref>{{cite web |url=http://www.nimh.nih.gov/news/science-news/2006/properly-timed-light-melatonin-lift-winter-depression-by-syncing-rhythms.shtml|title=Properly Timed Light, Melatonin Lift Winter Depression by Syncing Rhythms |author=<!--Staff writer(s); no by-line.--> |date=1 May 2006 |website=NIMH Science News|publisher=The National Institute of Mental Health (NIMH) |access-date=9 December 2014}}</ref>

===Light therapy===
Photoperiod-related alterations of the duration of melatonin secretion may affect the seasonal mood cycles of SAD. This suggests that light therapy may be an effective treatment for SAD.<ref>{{cite journal | vauthors = Howland RH | title = Somatic therapies for seasonal affective disorder | journal = Journal of Psychosocial Nursing and Mental Health Services | volume = 47 | issue = 1 | pages = 17–20 | date = January 2009 | pmid = 19227105 | doi = 10.3928/02793695-20090101-07 }}</ref> Light therapy uses a [[light therapy|lightbox]], which emits far more [[Lumen (unit)|lumens]] than a customary incandescent lamp. Bright white [[Full-spectrum light|"full spectrum"]] light at 10,000 lux, blue light at a wavelength of 480nm at 2,500 lux or green (actually cyan or blue-green<ref>{{cite web |vauthors=Jones AZ |title=The Visible Light Spectrum |url=http://physics.about.com/od/lightoptics/a/vislightspec.htm |date=February 15, 2012 |access-date=February 15, 2012 |archive-date=January 3, 2012 |archive-url=https://web.archive.org/web/20120103185102/http://physics.about.com/od/lightoptics/a/vislightspec.htm |url-status=dead }}</ref>) light at a wavelength of 500nm at 350 lux are used, with the first-mentioned historically preferred.<ref name = "Saeeduddin">{{cite journal | vauthors = Loving RT, Kripke DF, Knickerbocker NC, Grandner MA | title = Bright green light treatment of depression for older adults [ISRCTN69400161] | journal = BMC Psychiatry | volume = 5 | pages = 42 | date = November 2005 | pmid = 16283926 | pmc = 1309618 | doi = 10.1186/1471-244X-5-42 | quote = Bright green light was not shown to have an antidepressant effect in the age group of this study, but a larger trial with brighter green light might be of value. | doi-access = free }}</ref><ref>{{cite journal | vauthors = Strong RE, Marchant BK, Reimherr FW, Williams E, Soni P, Mestas R | title = Narrow-band blue-light treatment of seasonal affective disorder in adults and the influence of additional nonseasonal symptoms | journal = Depression and Anxiety | volume = 26 | issue = 3 | pages = 273–8 | year = 2009 | pmid = 19016463 | doi = 10.1002/da.20538 | s2cid = 40649124 | doi-access = free }}</ref>

Bright light therapy is effective<ref name = "Avery2"/> with the patient sitting a prescribed distance, commonly 30–60&nbsp;cm, in front of the box with their eyes open, but not staring at the light source,<ref name = "Avery"/> for 30–60 minutes. A study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination.<ref name="doi101126">{{cite journal | vauthors = Gooley JJ, Rajaratnam SM, Brainard GC, Kronauer RE, Czeisler CA, Lockley SW | title = Spectral responses of the human circadian system depend on the irradiance and duration of exposure to light | journal = Science Translational Medicine | volume = 2 | issue = 31 | pages = 31ra33 | date = May 2010 | pmid = 20463367 | pmc = 4414925 | doi = 10.1126/scitranslmed.3000741 }}</ref> Discovering the best schedule is essential. One study has shown that up to 69% of patients find lightbox treatment inconvenient, and as many as 19% stop use because of this.<ref name = "Avery"/>

[[Dawn simulation]] has also proven to be effective; in some studies, there is an 83% better response when compared to other bright light therapy.<ref name = "Avery"/> When compared in a study to [[negative air ionization therapy|negative air ionization]], bright light was shown to be 57% effective vs. dawn simulation 50%.<ref name = "Terman">{{cite journal | vauthors = Terman M, Terman JS | title = Controlled trial of naturalistic dawn simulation and negative air ionization for seasonal affective disorder | journal = The American Journal of Psychiatry | volume = 163 | issue = 12 | pages = 2126–2133 | date = December 2006 | pmid = 17151164 | doi = 10.1176/appi.ajp.163.12.2126 }}</ref> Patients using light therapy can experience improvement during the first week, but increased results are evident when continued throughout several weeks.<ref name = "Avery"/> Certain symptoms like hypersomnia, early insomnia, social withdrawal, and anxiety resolve more rapidly with light therapy than with [[cognitive behavioral therapy]].<ref>{{cite journal | vauthors = Meyerhoff J, Young MA, Rohan KJ | title = Patterns of depressive symptom remission during the treatment of seasonal affective disorder with cognitive-behavioral therapy or light therapy | journal = Depression and Anxiety | volume = 35 | issue = 5 | pages = 457–467 | date = May 2018 | pmid = 29659120 | pmc = 5934317 | doi = 10.1002/da.22739 }}</ref> Most studies have found it effective without use year round, but rather as a seasonal treatment lasting for several weeks, until frequent light exposure is naturally obtained.<ref name = "Lam"/>

[[Light therapy]] can also consist of exposure to sunlight, either by spending more time outside<ref>{{cite web | vauthors = Beck M | date = 1 December 2009 | url = https://www.wsj.com/articles/SB10001424052748703300504574567881192085174?mod=rss_Today%27s_Most_Popular | title = Exercise outdoors: Bright Ideas for Treating the Winter Blues | work = The Wall Street Journal }}</ref> or using a computer-controlled [[heliostat]] to reflect sunlight into the windows of a home or office.<ref>{{cite web | url = http://www.practicalsolar.com/applications.html | title = Applications: Health | access-date = June 9, 2009 | publisher = Practical Solar | url-status = dead | archive-url = https://web.archive.org/web/20090615153220/http://www.practicalsolar.com/applications.html | archive-date = June 15, 2009 | df = mdy-all }}</ref><ref>{{cite web | url = http://www.newyorkhousemagazine.com/pages/full_story?page_label=home_main_top&id=2631630&widget=push&instance=home_green_future&article-Grab%20the%20Sun%20With%20Heliostats%20=&open=& | archive-url = https://web.archive.org/web/20091004205721/http://www.newyorkhousemagazine.com/pages/full_story?page_label=home_main_top&id=2631630&widget=push&instance=home_green_future&article-Grab%20the%20Sun%20With%20Heliostats%20=&open=& | url-status = dead | archive-date = October 4, 2009 | title = Grab the Sun With Heliostats | publisher = New York House | access-date = December 8, 2009 | date = June 1, 2009 }}</ref> Although light therapy is the leading treatment for seasonal affective disorder, prolonged direct sunlight or artificial lights that don't block the ultraviolet range should be avoided, due to the threat of [[skin cancer]].<ref>{{cite journal | vauthors = Osborn J, Raetz J, Kost A | title = Seasonal affective disorder, grief reaction, and adjustment disorder | journal = The Medical Clinics of North America | volume = 98 | issue = 5 | pages = 1065–77 | date = September 2014 | pmid = 25134873 | doi = 10.1016/j.mcna.2014.06.006 }}</ref>

The evidence base for light therapy as a preventive treatment for seasonal affective disorder is limited.<ref name=":0">{{cite journal | vauthors = Nussbaumer-Streit B, Forneris CA, Morgan LC, Van Noord MG, Gaynes BN, Greenblatt A, Wipplinger J, Lux LJ, Winkler D, Gartlehner G | display-authors = 6 | title = Light therapy for preventing seasonal affective disorder | journal = The Cochrane Database of Systematic Reviews | volume = 3 | pages = CD011269 | date = March 2019 | issue = 4 | pmid = 30883670 | pmc = 6422319 | doi = 10.1002/14651858.CD011269.pub3 }}</ref> The decision to use light therapy to treat people with a history of winter depression before depressive symptoms begin should be based on a person's preference of treatment.<ref name=":0" />

===Medication===
[[Selective serotonin reuptake inhibitor|SSRI]] (selective serotonin reuptake inhibitor) antidepressants have proven effective in treating SAD.<ref name = "Modell"/> Effective antidepressants are [[fluoxetine]], [[sertraline]], or [[paroxetine]].<ref name = "Lam"/><ref>{{cite journal | vauthors = Moscovitch A, Blashko CA, Eagles JM, Darcourt G, Thompson C, Kasper S, Lane RM | title = A placebo-controlled study of sertraline in the treatment of outpatients with seasonal affective disorder | journal = Psychopharmacology | volume = 171 | issue = 4 | pages = 390–397 | date = February 2004 | pmid = 14504682 | doi = 10.1007/s00213-003-1594-8 | author8 = International Collaborative Group on Sertraline in the Treatment of Outpatients with Seasonal Affective Disorders | s2cid = 683231 }}</ref> Both fluoxetine and light therapy are 67% effective in treating SAD, according to direct head-to-head trials conducted during the 2006 Can-SAD study.<ref>{{cite journal | vauthors = Lam RW, Levitt AJ, Levitan RD, Enns MW, Morehouse R, Michalak EE, Tam EM | title = The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder | journal = The American Journal of Psychiatry | volume = 163 | issue = 5 | pages = 805–812 | date = May 2006 | pmid = 16648320 | doi = 10.1176/appi.ajp.163.5.805 }}</ref> Subjects using the light therapy protocol showed earlier clinical improvement, generally within one week of beginning the clinical treatment.<ref name = "Lam"/> [[Bupropion]] extended-release has been shown to prevent SAD for one in four people, but has not been compared directly to other preventive options in trials.<ref>{{cite journal | vauthors = Gartlehner G, Nussbaumer-Streit B, Gaynes BN, Forneris CA, Morgan LC, Greenblatt A, Wipplinger J, Lux LJ, Van Noord MG, Winkler D | display-authors = 6 | title = Second-generation antidepressants for preventing seasonal affective disorder in adults | journal = The Cochrane Database of Systematic Reviews | volume = 3 | pages = CD011268 | date = March 2019 | issue = 4 | pmid = 30883669 | pmc = 6422318 | doi = 10.1002/14651858.CD011268.pub3 }}</ref> In a 2021 updated Cochrane review of [[second-generation antidepressant]] medications for the treatment of SAD, a definitive conclusion could not be drawn, due to lack of evidence, and the need for larger randomized controlled trials.<ref>{{cite journal | vauthors = Nussbaumer-Streit B, Thaler K, Chapman A, Probst T, Winkler D, Sönnichsen A, Gaynes BN, Gartlehner G | display-authors = 6 | title = Second-generation antidepressants for treatment of seasonal affective disorder | journal = The Cochrane Database of Systematic Reviews | volume = 2021 | issue = 3 | pages = CD008591 | date = March 2021 | pmid = 33661528 | pmc = 8092631 | doi = 10.1002/14651858.CD008591.pub3 }}</ref>

[[Modafinil]] may be an effective and well-tolerated treatment in patients with seasonal affective disorder/winter depression.<ref>{{cite journal | vauthors = Lundt L | title = Modafinil treatment in patients with seasonal affective disorder/winter depression: an open-label pilot study | journal = Journal of Affective Disorders | volume = 81 | issue = 2 | pages = 173–8 | date = August 2004 | pmid = 15306145 | doi = 10.1016/S0165-0327(03)00162-9 }}</ref>

Another explanation is that [[vitamin D]] levels are too low when people do not get enough [[Ultraviolet#Vitamin D|Ultraviolet-B on their skin]]. An alternative to using bright lights is to take vitamin D supplements.<ref>{{cite journal | vauthors = Wilkins CH, Sheline YI, Roe CM, Birge SJ, Morris JC | title = Vitamin D deficiency is associated with low mood and worse cognitive performance in older adults | journal = The American Journal of Geriatric Psychiatry | volume = 14 | issue = 12 | pages = 1032–40 | date = December 2006 | pmid = 17138809 | doi = 10.1097/01.JGP.0000240986.74642.7c | s2cid = 19008379 }}</ref><ref>{{cite journal | vauthors = Lansdowne AT, Provost SC | title = Vitamin D3 enhances mood in healthy subjects during winter | journal = Psychopharmacology | volume = 135 | issue = 4 | pages = 319–23 | date = February 1998 | pmid = 9539254 | doi = 10.1007/s002130050517 | s2cid = 21227712 }}</ref><ref>{{cite journal | vauthors = Gloth FM, Alam W, Hollis B | title = Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder | journal = The Journal of Nutrition, Health & Aging | volume = 3 | issue = 1 | pages = 5–7 | year = 1999 | pmid = 10888476 }}</ref> However, studies did not show a link between vitamin D levels and depressive symptoms in elderly Chinese,<ref>{{cite journal | vauthors = Pan A, Lu L, Franco OH, Yu Z, Li H, Lin X | title = Association between depressive symptoms and 25-hydroxyvitamin D in middle-aged and elderly Chinese | journal = Journal of Affective Disorders | volume = 118 | issue = 1–3 | pages = 240–3 | date = November 2009 | pmid = 19249103 | doi = 10.1016/j.jad.2009.02.002 }}
*{{lay source |template = cite press release|url = https://www.sciencedaily.com/releases/2009/03/090317142847.htm|title = Vitamin D May Not Be The Answer To Feeling SAD|date = March 18, 2009 |website = Science Daily}}</ref> nor among elderly British women given only 800IU when 6,000IU is needed.<ref>{{cite journal | vauthors = Dumville JC, Miles JN, Porthouse J, Cockayne S, Saxon L, King C | title = Can vitamin D supplementation prevent winter-time blues? A randomised trial among older women | journal = The Journal of Nutrition, Health & Aging | volume = 10 | issue = 2 | pages = 151–3 | year = 2006 | pmid = 16554952 }}</ref> 5-HTP (an amino acid that helps to produce serotonin, and is often used to help those with depression) has also been suggested as a supplement that may help treat the symptoms of SAD, by lifting mood, and regulating sleep schedule for those with the condition.<ref>{{Cite web|title=Don't be SAD: seasonal affective disorder advice|url=https://www.medino.com/article/seasonal-affective-disorder-advice|access-date=2021-05-19|website=medino|language=en}}</ref> However, those who take antidepressants are not advised to take 5-HTP, as antidepressant medications may combine with the supplement to create dangerously high levels of serotonin – potentially resulting in [[serotonin syndrome]].<ref>{{Cite news|title=5-HTP Safety Concerns|url=https://www.poison.org/articles/5htp-safety-concerns-173|access-date=2021-05-19|website=www.poison.org|language=en}}</ref>

===Other treatments===
Depending upon the patient, one treatment (e.g., lightbox) may be used in conjunction with another (e.g., medication).<ref name = "Lam"/>

[[Air ioniser|Negative air ionization]], which involves releasing charged particles into the sleep environment, has been found effective, with a 47.9% improvement if the negative ions are in sufficient density (quantity).<ref name="Terman" /><ref name="doi 10.1001/archpsyc.55.10.875">{{cite journal | vauthors = Terman M, Terman JS, Ross DC | title = A controlled trial of timed bright light and negative air ionization for treatment of winter depression | journal = Archives of General Psychiatry | volume = 55 | issue = 10 | pages = 875–82 | date = October 1998 | pmid = 9783557 | doi = 10.1001/archpsyc.55.10.875 | s2cid = 18127922 | doi-access =  }}</ref><ref name="ReferenceA">{{cite journal | vauthors = Terman M, Terman JS | title = Treatment of seasonal affective disorder with a high-output negative ionizer | journal = Journal of Alternative and Complementary Medicine | volume = 1 | issue = 1 | pages = 87–92 | date = January 1995 | pmid = 9395604 | doi = 10.1089/acm.1995.1.87 }}</ref>

[[Exercise|Physical exercise]] has shown to be an effective form of depression therapy, particularly when in addition to another form of treatment for SAD.<ref>{{cite journal | vauthors = Pinchasov BB, Shurgaja AM, Grischin OV, Putilov AA | title = Mood and energy regulation in seasonal and non-seasonal depression before and after midday treatment with physical exercise or bright light | journal = Psychiatry Research | volume = 94 | issue = 1 | pages = 29–42 | date = April 2000 | pmid = 10788675 | doi = 10.1016/S0165-1781(00)00138-4 | s2cid = 12731381 }}</ref> One particular study noted marked effectiveness for treatment of depressive symptoms, when combining regular exercise with bright light therapy.<ref>{{cite journal | vauthors = Leppämäki S, Partonen T, Lönnqvist J | title = Bright-light exposure combined with physical exercise elevates mood | journal = Journal of Affective Disorders | volume = 72 | issue = 2 | pages = 139–44 | date = November 2002 | pmid = 12200204 | doi = 10.1016/S0165-0327(01)00417-7 }}</ref> Patients exposed to exercise which had been added to their treatments in 20 minutes intervals on the aerobic bike during the day, along with the same amount of time underneath the [[Ultraviolet|UV light]] were seen to make a quick recovery.<ref>{{cite journal | vauthors = Roecklein KA, Rohan KJ | title = Seasonal affective disorder: an overview and update | journal = Psychiatry | volume = 2 | issue = 1 | pages = 20–6 | date = January 2005 | pmid = 21179639 | pmc = 3004726 }}</ref>

Of all the psychological therapies aimed at the prevention of SAD, cognitive-behavior therapy, typically involving thought records, activity schedules and a positive data log, has been the subject of the most empirical work. However, evidence for cognitive behavioral therapy or any of the psychological therapies aimed at preventing SAD remains inconclusive.<ref>{{Cite journal |last1=Forneris |first1=Catherine A. |last2=Nussbaumer-Streit |first2=Barbara |last3=Morgan |first3=Laura C. |last4=Greenblatt |first4=Amy |last5=Van Noord |first5=Megan G. |last6=Gaynes |first6=Bradley N. |last7=Wipplinger |first7=Jörg |last8=Lux |first8=Linda J. |last9=Winkler |first9=Dietmar |last10=Gartlehner |first10=Gerald |date=2019-05-24 |title=Psychological therapies for preventing seasonal affective disorder |journal=The Cochrane Database of Systematic Reviews |volume=2019 |issue=5 |pages=CD011270 |doi=10.1002/14651858.CD011270.pub3 |issn=1469-493X |pmc=6533196 |pmid=31124141}}</ref>

==Epidemiology==

===Nordic countries===
Winter depression is a common slump in the mood of some inhabitants of most of the [[Nordic countries]]. [[Iceland]], however, seems to be an exception. A study of more than 2000 people there found the prevalence of seasonal affective disorder and seasonal changes in anxiety and depression to be unexpectedly ''low'' in both sexes.<ref>{{cite journal | vauthors = Magnusson A, Axelsson J, Karlsson MM, Oskarsson H | title = Lack of seasonal mood change in the Icelandic population: results of a cross-sectional study | journal = The American Journal of Psychiatry | volume = 157 | issue = 2 | pages = 234–8 | date = February 2000 | pmid = 10671392 | doi = 10.1176/appi.ajp.157.2.234 | s2cid = 20441380 }}</ref> The study's authors suggested that propensity for SAD may differ due to some genetic factor within the Icelandic population. A study of Canadians of wholly Icelandic descent also showed low levels of SAD.<ref name="pmid8250680">{{cite journal | vauthors = Magnússon A, Axelsson J | title = The prevalence of seasonal affective disorder is low among descendants of Icelandic emigrants in Canada | journal = Archives of General Psychiatry | volume = 50 | issue = 12 | pages = 947–51 | date = December 1993 | pmid = 8250680 | doi = 10.1001/archpsyc.1993.01820240031004 }}</ref> It has more recently been suggested that this may be attributed to the large amount of fish traditionally eaten by Icelandic people. In 2007, about 90 kilograms of fish per person was consumed per year in Iceland, as opposed to about 24 kilograms in the US and Canada,<ref name=fao>[https://web.archive.org/web/20170519070616/ftp://ftp.fao.org/FI/CDrom/CD_yearbook_2008/root/food_balance/section2.pdf Fishery and Aquaculture Statistics: SECTION 2 – Food balance sheets and fish contribution to protein supply, by country from 1961 to 2007] . Rome: Food and Agriculture Organization of the United Nations (2008)</ref> rather than to genetic predisposition; a similar anomaly is noted in Japan, where annual fish consumption in recent years averages about 60 kilograms per capita.<ref>{{cite journal | vauthors = Cott J, Hibbeln JR | title = Lack of seasonal mood change in Icelanders | journal = The American Journal of Psychiatry | volume = 158 | issue = 2 | pages = 328 | date = February 2001 | pmid = 11156835 | doi = 10.1176/appi.ajp.158.2.328 }}</ref>  Fish are high in [[vitamin D]]. Fish also contain [[docosahexaenoic acid]] (DHA), which helps with a variety of neurological dysfunctions.<ref>{{cite journal | vauthors = Horrocks LA, Yeo YK | title = Health benefits of docosahexaenoic acid (DHA) | journal = Pharmacological Research | volume = 40 | issue = 3 | pages = 211–25 | date = September 1999 | pmid = 10479465 | doi = 10.1006/phrs.1999.0495 | citeseerx = 10.1.1.334.6891 }}</ref>{{dubious|date=November 2020}}

===Other countries===
In the United States, a diagnosis of seasonal affective disorder was first proposed by [[Norman E. Rosenthal]], M.D. in 1984. Rosenthal wondered why he became sluggish during the winter after moving from sunny [[South Africa]] to (cloudy in winter) [[New York (state)|New York]]. He started experimenting with increasing exposure to artificial light, and found this made a difference. In [[Alaska]] it has been established that there is a SAD rate of 8.9%, and an even greater rate of 24.9%<ref>[http://www.britebox.co.uk/sad-study.php?page=latitude SAD Treatment | SAD Lamp | SAD Light | SAD Cure | Seasonal Affected Disorder Britebox Energise Case Study] {{webarchive|url=https://web.archive.org/web/20110810084450/http://www.britebox.co.uk/sad-study.php?page=latitude |date=August 10, 2011 }}. Britebox.co.uk. Retrieved on March 24, 2013.</ref> for subsyndromal SAD.

Around 20% of [[Irish people]] are affected by SAD, according to a survey conducted in 2007. The survey also shows women are more likely to be affected by SAD than men.<ref>[https://www.irishexaminer.com/news/arid-30335888.html One in five suffers from SAD]. Irish Examiner (November 10, 2007). Retrieved on March 24, 2013.</ref>{{Better source needed|date=January 2021}} An estimated 3% of the population in the [[Netherlands]] experience winter SAD.<ref name="pmid10386184">{{cite journal | vauthors = Mersch PP, Middendorp HM, Bouhuys AL, Beersma DG, van den Hoofdakker RH | title = The prevalence of seasonal affective disorder in The Netherlands: a prospective and retrospective study of seasonal mood variation in the general population | journal = Biol. Psychiatry | volume = 45 | issue = 8 | pages = 1013–22 | date = April 1999 | pmid = 10386184 | doi = 10.1016/s0006-3223(98)00220-0 | s2cid = 21467329 | url = https://pure.rug.nl/ws/files/10517302/1999BiolPsychiatMersch.pdf | hdl = 11370/31c5324d-4415-4980-9fb0-cd8f3b700b77 | hdl-access = free }}</ref>

== History ==
SAD was formally described and named in 1984 by [[Norman E. Rosenthal]] and his colleagues at the [[National Institute of Mental Health]].<ref name="Rosenthal, NE 1984">
{{cite journal |vauthors=Rosenthal NE, Sack DA, Gillin JC, Lewy AJ, Goodwin FK, Davenport Y, Mueller PS, Newsome DA, Wehr TA |date=January 1984 |title=Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy |journal=Archives of General Psychiatry |volume=41 |issue=1 |pages=72–80 |doi=10.1001/archpsyc.1984.01790120076010 |pmc=2686645 |pmid=6581756}}</ref><ref name="Marshall2003">Marshall, Fiona. Cheevers, Peter (2003). "Positive options for Seasonal Affective Disorder", p. 77. Hunter House, Alameda, Calif. {{ISBN|0-89793-413-X}}.</ref> The initial investigation was motivated by observations of depression occurring during the dark winter months in northern regions of the United States, known as [[polar night]]. Rosenthal proposed that the reduction in available natural light during winter could contribute to this phenomenon. Subsequently, he and his colleagues conducted a [[placebo-controlled study]] that utilized light [[therapy]] to document the effects of the condition.<ref name="Rosenthal, NE 1984" /><ref name="Marshall2003" /> Although Rosenthal's ideas were initially greeted with skepticism, SAD has become well recognized. His 1993 book ''Winter Blues''<ref>{{cite book |author-link=Norman E. Rosenthal |url=https://archive.org/details/winterbluesrevis00norm |title=Winter Blues: Everything You Need to Know to Beat Seasonal Affective Disorder |vauthors=Rosenthal NE |publisher=The Guilford Press |year=2006 |isbn=978-1593852146 |edition=Revised |location=New York |url-access=registration}}</ref> has become the standard introduction to the subject.<ref>{{cite news |date=December 26, 1994 |title=It's Wintertime: When Winter Falls, Many Find Themselves In Need Of Light |work=Milwaukee Sentinel |publisher=Gannett News Service |vauthors=More LK}}</ref>

Research on SAD in the United States began in 1979 when Herb Kern, a research engineer, noticed he felt depressed during the winter months. Kern suspected that scarcer natural light in winter was the cause and discussed the idea with NIMH scientists working on bodily rhythms. They were intrigued and responded by inventing a lightbox to treat Kern's depression, which improved.<ref name="Marshall2003" /><ref>{{cite book |title=An Oral History of Neuropsychopharmacology, The First Fifty Years, Peer Interviews |vauthors=Ban TA |publisher=American College of Neuropsychopharmacology |year=2011 |veditors=Gershon S |volume=5}}{{page needed|date=April 2019}}</ref>

SAD is usually more common in the fall/winter (Winter SAD), though it may occur during the spring/summer (Spring SAD). Winter-onset SAD is more common and is often characterized by atypical depressive symptoms including hypersomnia, increased appetite, and craving for carbohydrates. Spring/summer SAD is also seen and is more frequently associated with typical depressive symptoms including insomnia and loss of appetite. <ref>{{Cite journal |date=2024-12-23 |title=Seasonal Affective Disorder (SAD): Background, Pathophysiology, Epidemiology |url=https://emedicine.medscape.com/article/2500054-overview?utm_source=chatgpt.com&form=fpf}}</ref>

== Criticism of disorder and diagnosis ==
{{Expand section|date=April 2025}}
The validity of SAD has been called into question multiple times. A 2008 study indicated that some people stay without sun for months, yet they are not affected by SAD.<ref>{{Cite journal |last=Hansen |first=Vidje |last2=Skre |first2=Ingunn |last3=Lund |first3=Eiliv |date=June 2008 |title=What is this thing called “SAD”? A critique of the concept of seasonal affective disorder |url=https://doi.org/10.1017/s1121189x00002815 |journal=Epidemiologia e Psichiatria Sociale |volume=17 |issue=2 |pages=120–127 |doi=10.1017/s1121189x00002815 |issn=1121-189X}}</ref> A 2016 analysis from the [[Center for Disease Control|Centers for Disease Control]] found no links between depression, seasonality or sunlight exposure and suggested discontinuation of the diagnosis. Further, a 2018 study focusing on instability of SAD diagnosis criteria over prolonged periods of time, suggested that SAD is a temporary expression of a mood disorder rather than a specific disorder.<ref name="Traffanstedt et al., 2016" /><ref>{{Cite journal |last1=Cléry-Melin |first1=Marie-Laure |last2=Gorwood |first2=Philip |last3=Friedman |first3=Serge |last4=Even |first4=Christian |date=February 2018 |title=Stability of the diagnosis of seasonal affective disorder in a long-term prospective study |url=https://linkinghub.elsevier.com/retrieve/pii/S0165032717306201 |journal=Journal of Affective Disorders |language=en |volume=227 |pages=353–357 |doi=10.1016/j.jad.2017.11.014|pmid=29145077 }}</ref>

== See also ==
* [[Diurnal cycle]]
* [[Seasonal effects on suicide rates]]
* [[Seasonal Pattern Assessment Questionnaire]]
* [[Vitamin D deficiency]]

== References ==
{{Reflist}}

== External links ==

* [https://www.nimh.nih.gov/health/topics/seasonal-affective-disorder/index.shtml Seasonal affective disorder] at the US [[National Institute of Mental Health]]

{{Medical resources
| ICD10 = {{ICD10|F|33||f|33}}
| MedlinePlus = 001532
}}
{{Authority control}}

[[Category:Circadian rhythm]]
[[Category:Major depressive disorder]]
[[Category:Mood disorders]]
[[Category:Weather and health]]