Midday Bright Light Therapy Improves Mood in Bipolar Depressed Patients

In a six-week, double-blind study, Dr. Sit and collaborators randomly assigned adults with bipolar depression to treatment with either 7,000-lux bright white light or 50-lux dim red placebo light (23 patients in each group). The treatment was administered midday because bright light exposure at that time “can phase-advance and increase the amplitude of nocturnal melatonin production in healthy subjects and in elderly patients with insomnia.” It can also improve “decreased awake time at night, increased sleep efficiency, and reduced wake time after sleep onset.” The duration of light therapy started at 15 minutes per session between 12:00 p.m. and 2:30 p.m, increased by 15 minutes weekly up, and then up to 60 minutes by week 4. The authors found higher remission rates (68.2% vs. 22.2%) and lower depression scores with bright light therapy compared to placebo light. There were not mood polarity switches. Bright light therapy had a large effect between week 4 and week 6 of treatment. The results of this study are important given the limited treatment options for depression in bipolar disorder. In their conclusion, the authors stated “given its efficacy, ease of use, and tolerability, midday light therapy is ideally suited for depressed patients with bipolar disorder, and it may eventually gain widened acceptance with improved practitioner awareness.”