Seasonal affective disorder: a clinical update

Seasonal affective disorder (SAD) consists of recurrent major depressive episodes in the fall/winter with remissions in spring/summer.

A Medline search was conducted to identify studies relating to clinical management of SAD using the Medical Subject Heading, seasonal affective disorder, and key words, depress* and season*, focusing on studies published in the past 10 years. The Cochrane library of systematic reviews was also searched for relevant studies.

A careful history is important to make the diagnosis and differentiate SAD from other similar conditions such as subsyndromal SAD and atypical depression. Seasonal patterns with winter worsening are also recognized in "nonseasonal" depression as well as many other psychiatric conditions, and comorbidity with SAD is common. The pathophysiology of SAD seems to be heterogeneous as research on circadian, neurotransmitter function and genetic hypotheses have shown discrepant results. A dual vulnerability model with differential loading on separate seasonal and depression factors has been proposed to explain these findings. Recent systematic reviews have shown that light therapy is an efficacious and well-tolerated treatment for SAD. There is also evidence for efficacy of pharmacotherapy to treat and prevent SAD. Clinical studies show equal effectiveness with light and antidepressants, so patient preference should be considered in the selection of initial treatment. Dawn stimulation, negative air ions, exercise and cognitve behaviour therapy are under investigation and may also be helpful treatments for SAD.

SAD is a common condition with significant psychosocial impairment. Clinicians should be vigilant in recognizing seasonal patterns of depressive episodes because there are effective, evidence-based treatments for SAD.