Researchers from the University of Pittsburgh School of Medicine’s Western Psychiatric Institute and Clinic studied nine women with bipolar disorder to examine the effects of light therapy in the morning or at midday on mood symptoms.
“There are limited effective treatments for the depressive phase of bipolar disorder,” said Dorothy Sit, M.D., assistant professor of psychiatry and the study’s first author. “While there are treatments that are effective for mania, the major problem is the depression, which can linger so long that it never really goes away.”
The study is published in the journal Bipolar Disorders.
Women with bipolar depression were given light boxes and instructed on how to use them at home. The women used the light boxes daily for two-week stretches of 15, 30 and 45 minutes. Some patients responded extremely well to the light therapy, and their symptoms of depression disappeared.
The responders to light therapy stayed on the light therapy for an additional three or four months. Four patients received morning light, and five used their light boxes at midday. Participants also continued to take their prescribed medications throughout the study period.
“Three of the women who received morning light initially developed what we call a mixed state, with symptoms of depression and mania that occur all at once – racing thoughts, irritability, sleeplessness, anxiety and low mood,” said Dr. Sit. “But when another group began with midday light therapy, we found a much more stable response.”
Of the nine women treated, six achieved some degree of response, with several reaching full recovery from depressive symptoms. While most attained their best recovery with midday light, a few responded more fully to a final adjustment to morning light.
“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,” said Dr. Sit. “Did we introduce light too early and disrupt circadian rhythms and sleep patterns?”
People with bipolar disorder are known to be sensitive to changes in outdoor ambient light and to seasonal changes. Researchers are asking whether the risk of suicide in patients with bipolar disorder could be linked to changes in light exposure.
“In our study, 44 percent of patients were full responders, and 22 percent were partial responders,” Dr. Sit and her colleagues write. “Light therapy, therefore, is an attractive and possibly effective augmentation strategy to improve the likelihood of full-treatment response.”
Optimal response was observed with midday light therapy for 45 or 60 minutes daily, noted Dr. Sit.