Mood and behavioral effects of four-week light treatment in winter depressives and controls.

This study investigated (1) the time-course and durability of antidepressant effects of bright light in winter depressives, and (2) the effects of bright light on mood and behavior in normal controls in a 4-week open treatment paradigm. Twelve subjects in a major depressive episode during recurrent major depressive or bipolar disorder with seasonal pattern and 12 control subjects received 2,500 lux light between 0600 and 0800 hours, while 12 controls arose at 0600 hours for quiet activities without exposure to bright light. In depressives, maximal decrements in depression ratings were not reached until the fourth week of treatment. Four depressives experienced clinically significant hypomanic symptoms. Controls treated with light demonstrated significantly higher clinician ratings of hypomanic symptoms than no-light controls. When depressives and controls were combined, seasonality, but not diagnosis, predicted the emergence of manic-like symptoms. Implications for bright light treatment in the clinical setting are discussed.