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Light Treatment Benefits Depression in Bipolar Disorder
By John Gever, Staff Writer, MedPage Today
January 04, 2008

PITTSBURGH, Jan. 4 -- Depression symptoms in women with bipolar disorder improved following light-box therapy delivered at midday, researchers here said.

Four of nine women exposed to 7,000 lux of light therapy for 15 to 60 minutes a day for up to six weeks had complete relief and two others showed partial responses, Dorothy Sit, M.D., of the University of Pittsburgh, and colleagues reported in the December issue of Bipolar Disorders.

Most of the improvements came with treatment delivered between noon and 2 p.m. The first four participants received treatment in the morning, but three of them developed symptoms of both mania and depression, forcing two to quit treatment entirely. The remaining patients were then treated at midday without manic flare-ups.

"We found the optimal response was at 7,000 lux midday light for 45 or 60 minutes," the researchers said.

Among nonresponders to the midday treatment, one had a full response when switched to a morning schedule, they said. Another had partial symptom relief with morning treatment.

Light therapy is used frequently in patients with seasonal affective disorder, and has been shown to be beneficial in some patients with nonseasonal unipolar depression as well. But it has not been well studied in bipolar depression, Dr. Sit said.

Patients were included in the current study if they had a diagnosis of type I or II bipolar disorder without a seasonal pattern and persistent depressive symptoms that had not responded adequately to other treatments. Those with other psychiatric or physical disorders, including recent drug abuse, were excluded. The women took antimanic drugs beginning four weeks before starting light therapy and continuing through the study period.

Treatment response was defined as improvement of at least 50% from baseline in scores on the Structured Interview Guide for the Hamilton Depression Scale with Atypical Depression Supplement.

Treatment began with a two-week run-in phase in which participants received 30 minutes of dim (50 lux) red light to serve as a control. Active treatment then began at 15 minutes daily for two weeks, followed by 30 minutes a day for two weeks and then 45 minutes a day for two weeks.

Most patients showed mild improvement during the run-in phase, with mean improvement in depression scores of 8.3 points from a mean at baseline of 27.2 points.

In two patients who showed partial responses at 45 minutes a day without adverse effects, the daily dose was increased further to 60 minutes. Both patients then had full responses.

Intended as a dose-finding pilot study, the protocol did not include a parallel control group. The researchers said the results justify a randomized, placebo-controlled trial to explore the effectiveness of midday light therapy in men as well as women.

Dr. Sit said that it was unlikely that spontaneous remission could account for the depression relief seen in the study. Such remissions do occur in bipolar depression, but much less frequently than the response rate seen in this study.

The most important adverse effects were the onset of mixed manic and depressive symptoms in three of four patients treated in the morning, and significant uterine bleeding in three patients.

The study experience with timing of treatment could be important for future research, Dr. Sit said. "People with bipolar disorder are exquisitely sensitive to morning light, so this profound effect of morning treatment leading to mixed states is very informative and forces us to ask more questions," she said. "Did we introduce light too early and disrupt circadian rhythms and sleep patterns?"

The researchers said their findings support an emerging theory that midday treatment suppresses manic symptoms by holding circadian rhythms steady, while light treatment early in the day destabilizes these rhythms. An opposing camp holds that phase advancement of circadian rhythms is essential to therapeutic responses in bipolar disorder.

The bleeding complications were not related to menstruation or malignancy. Their origin remains unknown, Dr. Sit said, although some cases have been reported previously in patients treated with light therapy.

"We probably need to track that more closely in future studies," she said.

Dr. Sit said she was now seeking funding for a randomized, controlled trial of light therapy in bipolar depression.

Source: Sit D, et al. Light therapy for bipolar disorder: a case series in women. Bipolar Disorders, 2007: 9: 918-27.
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