A Possible New Treatment for Bipolar Depression

Individuals with bipolar disorder suffer from manic episodes, depressed episodes, and, sometimes, “mixed” episodes that include symptoms of both depression and mania. The number and length of episodes vary dramatically among individuals.

Most persons with bipolar disorder require mood stabilizing medications such as lithium, mood-stabilizing anticonvulsants, and/or antipsychotic drugs. Mood stabilizers are not very effective in treating the depressive symptoms of bipolar disorder. Although there is little evidence to support the use of antidepressants in treating the depressed phase of bipolar disorder, many clinicians prescribe antidepressants even though there is a risk of triggering a manic episode. Clearly, there is a need for more effective options for treating bipolar depression.

In a recent paper published in the American Journal of Psychiatry, Dorothy Sit, Katherine Wisner, and colleagues reported that bright light therapy may lead to substantial improvement in the symptoms of bipolar depression. The timing of the light therapy appears to be critical. Earlier work showed that bright light therapy administered in the morning was not effective and may have even triggered manic episodes. However, Sit’s group found that light therapy administered between noon and 2:30 p.m. was effective.

In their study, individuals increased their exposure to bright white light (7000 lux) from 15 minutes to 60 minutes a day over a four-week period. After six weeks of treatment, about 68 percent of those with a moderate severity of depressive symptoms were in remission compared to 22 percent who received placebo (red light) treatments. Interestingly, most of the improvement occurred during weeks four to six. The study ended at six weeks and it is possible that an even higher number of participants would have remitted after several more weeks of treatment. There were no reports of serious side effects. All participants in the study were on stable doses of mood stabilizing medications, and some were also taking antidepressant medications. The participants taking antidepressants were equally distributed between the treatment and placebo groups. No changes in pharmacologic treatment were made for any participant during the study period.

The mechanism underlying improvement with light therapy in individuals with bipolar depression is unknown. It is possible that midday light treatment regulates internal body clocks that are thought to be dysregulated by the illness. It is interesting that there appears to be a substantial difference when the treatments occur midday versus in the morning.

Bipolar depression can be disabling and difficult to treat. If these results are confirmed, there may be a safe, affordable, and effective treatment for this serious condition.

This column was written by Eugene Rubin MD, Ph.D., and Charles Zorumski, MD.