Midday Bright Light Therapy Improved Bipolar Depression
A study by Dorothy K. Sit and colleagues published in the American Journal of Psychiatry in 2017 found that delivering bright white light therapy to patients with bipolar depression between the hours of noon and 2:30pm improved their depression compared to delivering inactive dim light, and did not cause mood switches into mania. The study included 46 patients with moderate bipolar depression, no hypomania and no psychosis.
The active therapy group was exposed to broad-spectrum bright white fluorescent light at 7,000 Lux while the inactive group received dim red light at 50 Lux. Both groups were instructed to sit 12 inches from the light and face it without looking directly at it. The therapy began with 15-minute afternoon sessions and increased to 60 minutes per day by 4 weeks. Participants were assessed weekly. Remission rates increased dramatically in the active group beginning in the fourth week. At weeks 4 through 6, the remission rate for those in the active bright light group was 68.2% compared to only 22.2% in the dim light group.
Mean depression scores were better in the treated group, as were global functioning and response rates.
Some participants were taking antidepressants concurrently, and these participants were evenly distributed across the two study groups.
An earlier pilot study by the same researchers had found that bright light therapy delivered in the morning was followed by some hypomanic reactions or bipolar cycling. The midday sessions did not cause any mood switching.
Bright light therapy is often used to treat seasonal affective disorder (SAD) using a 10,000 Lux light box. This study took place mostly during the fall and winter months.
Editor’s Note: Bright light therapy is generally safe and boasts a high remission rate. Light boxes can be acquired without a prescription and are portable and easy to use. Midday light may have the best results and the least risk of provoking a mood switch into mania.
