Long-term and preventative treatment for seasonal affective disorder

Recurrent major depressive disorder with regular seasonal patterns, commonly known as seasonal affective disorder (SAD), has evoked substantial research in the last two decades. It is now recognised that SAD is a common condition with prevalence rates between 0.4% and 2.9% of the general population, and that patients with SAD experience significant morbidity and impairment in psychosocial function. There is good evidence that bright light therapy and antidepressant medications are effective for the short-term treatment of SAD; however, given that SAD is characterised by recurrent major depressive episodes, long-term and maintenance treatment must be considered. Unfortunately, there are few studies of longer term (>8 weeks) and maintenance (preventative) treatments for SAD. The weight of evidence suggests that light therapy usually needs to be continued daily throughout the winter season because of rapid relapse when light is stopped too early in the treatment period. However, some studies support the use of antidepressants to continue the response from a brief (1-2 weeks) course of light therapy early in the depressive episode, as soon as the first symptoms emerge in autumn. Only small studies have examined preventative treatment (before onset of symptoms) with light therapy, all of which have methodological limitations. The best evidence for preventative treatment in SAD comes from antidepressant studies. Three large, randomised, placebo-controlled studies have shown that preventative treatment with bupropion XL reduces the recurrence rate of depressive episodes in patients with SAD. Given the limitations in the evidence base and the inconsistent recurrence rate of winter depressive episodes, clinical recommendations for long-term and preventative treatment must individualise treatment choices and weigh potential benefits against possible adverse effects.