Lifetime estimates for depressive and bipolar disorders with a seasonal pattern average between 0.4% and 2.9% in US, Canadian, and UK community studies.[1]Blazer DG, Kessler RC, Swartz MS. Epidemiology of recurrent major and minor depression with a seasonal pattern: the National Comorbidity Survey. Br J Psychiatry. 1998 Feb;172:164-7.
http://www.ncbi.nlm.nih.gov/pubmed/9519070?tool=bestpractice.com
[2]Levitt AJ, Boyle MH, Joffe RT, et al. Estimated prevalence of the seasonal subtype of major depression in a Canadian community sample. Can J Psychiatry. 2000 Sep;45(7):650-4.
http://www.ncbi.nlm.nih.gov/pubmed/11056828?tool=bestpractice.com
[3]Levitt AJ, Boyle MH. The impact of latitude on the prevalence of seasonal depression. Can J Psychiatry. 2002 May;47(4):361-7.
http://www.ncbi.nlm.nih.gov/pubmed/12025435?tool=bestpractice.com
[4]Michalak EE, Lam RW. Seasonal affective disorder: the latitude hypothesis revisited. Can J Psychiatry. 2002 Oct;47(8):787-8.
http://www.ncbi.nlm.nih.gov/pubmed/12420660?tool=bestpractice.com
Some estimates may be as high 9.7%.[5]Magnusson A, Axelsson J, Karlsson MM, et al. Lack of seasonal mood change in the Icelandic population: results of a cross-sectional study. Am J Psychiatry. 2000 Feb;157(2):234-8.
http://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.157.2.234
http://www.ncbi.nlm.nih.gov/pubmed/10671392?tool=bestpractice.com
However, this is likely to be due to differences in the sampling and diagnostic criteria used. Rates of SAD may be slightly higher among people living in more northern latitudes.[6]Mersch PP, Middendorp HM, Bouhuys AL, et al. Seasonal affective disorder and latitude: a review of the literature. J Affect Disord. 1999 Apr;53(1):35-48.
http://www.ncbi.nlm.nih.gov/pubmed/10363665?tool=bestpractice.com
Although the latitude-SAD association has been demonstrated in North American samples, this finding has not been reliably replicated in European cohorts. This suggests the influence of other factors, such as genetic variability, cultural differences, and climate.[6]Mersch PP, Middendorp HM, Bouhuys AL, et al. Seasonal affective disorder and latitude: a review of the literature. J Affect Disord. 1999 Apr;53(1):35-48.
http://www.ncbi.nlm.nih.gov/pubmed/10363665?tool=bestpractice.com
[7]Radua J, Pertusa A, Cardoner N. Climatic relationships with specific clinical subtypes of depression. Psychiatry Res. 2010 Feb 28;175(3):217-20.
http://www.ncbi.nlm.nih.gov/pubmed/20045197?tool=bestpractice.com
Autumn or winter onset of major depressive episodes is much more common than other seasonal-mood fluctuations.[8]Wehr TA, Sack DA, Rosenthal NE. Seasonal affective disorder with summer depression and winter hypomania. Am J Psychiatry. 1987 Dec;144(12):1602-3.
http://www.ncbi.nlm.nih.gov/pubmed/3688288?tool=bestpractice.com
[9]Winkler D, Pjrek E, Iwaki R, et al. Treatment of seasonal affective disorder. Expert Rev Neurother. 2006 Jul;6(7):1039-48.
http://www.ncbi.nlm.nih.gov/pubmed/16831117?tool=bestpractice.com
Approximately 20% of people with SAD have a bipolar I or II disorder, with SAD being more likely in bipolar II disorder.[10]White DM, Lewy AJ, Sack RL, et al. Is winter depression a bipolar disorder? Compr Psychiatry. 1990 May-Jun;31(3):196-204.
http://www.ncbi.nlm.nih.gov/pubmed/2340714?tool=bestpractice.com
The incidence of SAD may be higher in some populations with anxiety, ADHD, and premenstrual dysphoric disorders.[11]Levitt AJ, Joffe RT, Brecher D, et al. Anxiety disorders and anxiety symptoms in a clinic sample of seasonal and non-seasonal depressives. J Affect Disord. 1993 May;28(1):51-6.
http://www.ncbi.nlm.nih.gov/pubmed/8326080?tool=bestpractice.com
[12]Amons PJ, Kooij JJ, Haffmans PM, et al. Seasonality of mood disorders in adults with lifetime attention-deficit/hyperactivity disorder (ADHD). J Affect Disord. 2006 Apr;91(2-3):251-5.
http://www.ncbi.nlm.nih.gov/pubmed/16458365?tool=bestpractice.com
[13]Praschak-Rieder N, Willeit M, Neumeister A, et al. Prevalence of premenstrual dysphoric disorder in female patients with seasonal affective disorder. J Affect Disord. 2001 Mar;63(1-3):239-42.
http://www.ncbi.nlm.nih.gov/pubmed/11246102?tool=bestpractice.com
Alcohol use may also increase as a means of self-medicating SAD symptoms in some populations.[14]Sher L. Alcoholism and seasonal affective disorder. Compr Psychiatry. 2004 Jan-Feb;45(1):51-6.
http://www.ncbi.nlm.nih.gov/pubmed/14671737?tool=bestpractice.com
The average age of onset is between 20 and 30 years, with declining rates in older populations.[15]Magnusson A, Partonen T. The diagnosis, symptomatology, and epidemiology of seasonal affective disorder. CNS Spectr. 2005 Aug;10(8):625-34.
http://www.ncbi.nlm.nih.gov/pubmed/16041294?tool=bestpractice.com
SAD is approximately 3 to 5 times more likely among women, which is a greater gender difference than that observed in non-seasonal depression.[16]Winkler D, Willeit M, Praschak-Rieder N, et al. Changes of clinical pattern in seasonal affective disorder (SAD) over time in a German-speaking sample. Eur Arch Psychiatry Clin Neurosci. 2002 Apr;252(2):54-62.
http://www.ncbi.nlm.nih.gov/pubmed/12111337?tool=bestpractice.com
The prevalence in children and adolescents ranges from 3.3% to 4.2%, with the incidence increasing among girls during puberty.[17]Swedo SE, Pleeter JD, Richter DM, et al. Rates of seasonal affective disorder in children and adolescents. Am J Psychiatry. 1995 Jul;152(7):1016-9.
http://www.ncbi.nlm.nih.gov/pubmed/7793436?tool=bestpractice.com
[18]Carskadon MA, Acebo C. Parental reports of seasonal mood and behavior changes in children. J Am Acad Child Adolesc Psychiatry. 1993 Mar;32(2):264-9.
http://www.ncbi.nlm.nih.gov/pubmed/8444753?tool=bestpractice.com
Other studies have noted that parental ratings of depression are more severe among 16- to 18-year-olds than among 6- to 15-year-olds when assessed during the fall and winter months.[19]Nillni YI, Rohan KJ, Rettew D, et al. Seasonal trends in depressive problems among United States children and adolescents: a representative population survey. Psychiatry Res. 2009 Dec 30;170(2-3):224-8.
http://www.ncbi.nlm.nih.gov/pubmed/19896720?tool=bestpractice.com
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