For people who suffer from winter depression, the most common type of seasonal affective disorder, bright-light therapy and Prozac are equally effective, Canadian researchers report in the American Journal of Psychiatry.

"This study gives patients with a common, but significantly debilitating mood disorder a choice between two effective treatments," Dr. Robert Freedman, editor-in-chief of the journal, said in a statement.

Winter depression is believed to be caused by heightened sensitivity to decreasing amounts of sunlight during the winter months and is characterized by depression, fatigue, food cravings, sleep disturbances, and social withdrawal.

The current study is not the first to evaluate bright-light therapy and Prozac as treatments for winter depression, yet few have directly compared the two, lead author Dr. Raymond W. Lam from the Mood Disorders Center in Vancouver, British Columbia, and colleagues note in their paper.

The researchers assessed the outcomes of 96 patients who were randomized to receive light therapy plus a placebo capsule or placebo light therapy plus Prozac (20 mg/day) for 8 weeks.
The light therapy was given for 30 minutes each morning using a fluorescent white-light box.
Light therapy and Prozac provided significant and comparable improvements in depressive symptoms, the report indicates. The clinical response rate in each group was 67 percent, while the remission rates hovered around 52 percent.

Further analysis indicated that light therapy provided a quicker initial improvement, but after 1 week, no differences were seen between the groups. Although both treatments were well tolerated with a comparable number of side effects, so-called "treatment-emergent" adverse events, including agitation and sleep disturbance, were more common with Prozac than with light therapy.

The researchers note that an ongoing analysis of data from the study should shed light on the factors that predict which therapy is most likely to be beneficial in a particular patient.