Seasonal affective disorder (SAD)


As we enter the shortest days of the year, some patients may experience depression and for many this is a recurring event. Recurrent major depressive disorder with seasonal pattern, more commonly known as seasonal affective disorder (SAD), affects two to three per cent of all Canadians.1 A milder form ("winter blues") affects up to 10 to 20 per cent.2 Symptoms generally occur in the fall or winter and remit by spring, though a minority of patients experience the opposite pattern (summer SAD). The incidence increases with latitude, and is more common between 20 and 50 years, and in women.1-3 The etiology of SAD remains unclear, but it is hypothesized that circadian rhythms and genetic factors are involved, and that serotonin, catecholamines, and melatonin also play a role.1


Light therapy remains one of the main treatments for winter SAD.4,5 However, questions remain about what is optimal light therapy (e.g. spectrum and intensity/dose).6,7 A Swedish health technology assessment found that light therapy improved depression scores in the first few weeks of therapy compared to placebo, but the effect diminished over time.5 Light therapy had no benefit when looking at clinical response (a 50 per cent reduction in depression score) as the outcome. Side effects, however, tend to be mild and include agitation, headache, eye strain and nausea. Hypomania has been reported with the initiation of light therapy. Blue wavelength light may harm the retina.


Various drug therapies have been studied for SAD (Table 1), with the majority of studies focusing on SSRIs and newer antidepressants. Although there are many reports of positive effects with medications, the quality of evidence overall is also poor. Of note, tricyclic antidepressants are not recommended since their sedating effects can exacerbate sleepiness and lethargy that accompanies SAD8, and there is a lack of evidence of benefit.


Extended-release bupropion is the only pharmacological therapy officially indicated for the prevention of SAD,9,10 although other serotonergic antidepressants may also be effective.11 Preventative treatment is usually started in the fall before the anticipated onset of symptoms, and tapered off in the spring, four to six months later.


Light therapy or drug therapy?

There are few direct comparisons between light therapy and medication so it is not possible to make a specific recommendation. Initial treatment decisions may be made on factors such as preference, convenience, and costs. Light therapy is considered generally "low risk",4 but does require a daily time commitment.12 A recent Canadian study comparing the total health care costs of light therapy versus fluoxetine (two therapies that have been reported to be equally effective) found that while purchasing a light box might cost more up front, after the first year of treatment light therapy starts to cost less, especially if fluoxetine doses are greater than 20 mg/d.13



Patients suffering from seasonal affective disorder may benefit from light or drug, but the overall quality of evidence, especially for drug therapy is low. Bupropion is the most effective drug treatment.



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  5. Gelenberg AJ, et al. Practice Guideline for the Treatment of Patients With Major Depressive Disorder, Third Edition. Available from URL: Accessed 15/11/2012.
  6. Swedish Council on Technology Assessment in Health Care. Light Therapy for Depression, and Other Treatment of Seasonal Affective Disorder. A Systematic Review. Accessed 08/11/2012.
  7. Anderson I, et al. Depression in adults (update): full guideline DRAFT (February 2009). Available from URL: Accessed 11/11/2012.
  8. Hairon, N. Helping patients to cope with seasonal affective disorder. Nursing Times. 2007;103: 25-26.
  9. Modell JG, et al. Seasonal affective disorder and its prevention by anticipatory treatment with bupropion XL. Biol Psychiatry. 2005;58:658-67.
  10. e-CPS
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  12. Thaler K, et al. Second-generation antidepressants for seasonal affective disorder. Cochrane Database Syst Rev. 2011;(12):CD008591.
  13. Cheung A, et al. Direct health care costs of treating seasonal affective disorder: a comparison of light therapy and fluoxetine. Depress Res Treat. 2012;2012:628434. doi: 10.1155/2012/628434. Epub 2012 Oct 18.
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  15. Ruhrmann S, et al. Effects of fluoxetine versus bright light in the treatment of seasonal affective disorder. Psychol Med. 1998 Jul;28(4):923-33.
  16. Lam RW, et al. Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder. Am J Psychiatry. 2006;163: 805-12
  17. Moscovitch A, et al. A placebo-controlled study of sertraline in the treatment of outpatients with seasonal affective disorder. Psychopharmacology (Berl). 2004;171:390-7.
  18. Pjrek E, et al. Escitalopram in seasonal affective disorder: results of an open trial. Pharmacopsychiatry. 2007;40:20-4.
  19. Pjrek E, et al. Treatment of seasonal affective disorder with duloxetine: an open-label study. Pharmacopsychiatry. 2008;41:100-5
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  22. Partonen T, Lönnqvist J. Moclobemide and fluoxetine in treatment of seasonal affective disorder. J Affect Disord. 1996 25;41:93-9
  23. Lewy AJ, et al. Melatonin treatment of winter depression: a pilot study. Psychiatry Res. 1998;77(1):57-61.
  24. Leppämäki S, et al. Effect of controlled-release melatonin on sleep quality, mood, and quality of life in subjects with seasonal or weather-associated changes in mood and behaviour. Eur Neuropsychopharmacol. 2003;13:137-45
  25. Kasper S. Treatment of Seasonal Affective Disorder (SAD) with Hypericum Extract. Pharmacopsychiatr. 1997; 30(Suppl): 89-93.
  26. Lingaerde O, et al. Can winter depression be prevented by Ginkgo biloba extract? A placebo-controlled trial. Acta Psychiatr Scand. 1999;100:62-6.
  27. Lansdowne AT, Provost SC. Vitamin D3 enhances mood in healthy subjects during winter. Psychopharmacology (Berl). 1998;135:319-323.
  28. Gloth FM 3rd, et al. Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder. J Nutr Health Aging. 1999;3(1):5-7.
  29. Dumville JC, et al. Can vitamin D supplementation prevent winter-time blues? A randomised trial among older women. J Nutr Health Aging. 2006;10:151-3.
  30. Lundt L. Modafinil treatment in patients with seasonal affective disorder/winter depression: an open-label pilot study. J Affect Disord. 2004;81:173-8.
  31. Ghadirian AM, et al. Efficacy of light versus tryptophan therapy in seasonal affective disorder. J Affect Disord. 1998;50:23-7.
  32. Hilger E, et al. Reboxetine in seasonal affective disorder: an open trial. Eur Neuropsychopharmacol. 2001;11:1-5.
  33. Yamadera H, et al. Open study of effects of alprazolam on seasonal affective disorder. Psychiatry Clin Neurosci. 2001;55:27-30.
  34. Oren DA, et al. A controlled trial of cyanocobalamin (vitamin B12) in the treatment of winter seasonal affective disorder. J Affect Disord. 1994 Nov;32(3):197-200.
  35. Oren DA, et al. A controlled trial of levodopa plus carbidopa in the treatment of winter seasonal affective disorder: a test of the dopamine hypothesis. J Clin Psychopharmacol. 1994;14:196-200.

©2013 B.C. Drug and Poison Information Centre

A version of this document was published in BCPhA's The Tablet. 2012; 21(6): 24-5.