Objectives: To perform a dose-ranging safety and efficacy study of bright light therapy for depression in women with bipolar disorder (BD).
Methods: Nine women with DSM-IV BD I or II in the depressed phase were exposed to 50 lux (illuminance at the receiving surface) red light for two weeks, after which they received 7,000 lux light therapy for two-week epochs of 15, 30 and 45 min daily. The Structured Interview Guide for the Hamilton Depression Rating Scale with Atypical Depression Supplement and the Mania Rating Scale were used to assess mood symptoms. Four patients received morning light and five patients received midday light.
Results: Three of the four subjects treated with morning light developed mixed states. The fourth subject achieved a full, sustained response. To decrease the risk of inducing mixed episodes, we changed the time of light exposure to midday. Of the five women who received midday light therapy, two achieved full response and two showed early improvement but required a dose increase to sustain response. One woman remained depressed with 45 min of midday light but responded fully to a switch to morning light, 30 min daily.
Conclusions: Women with bipolar illness are highly sensitive to morning bright light treatment; the induction of mixed states is a substantial risk. Initiating treatment with a brief duration (15 min) of midday light for bipolar depression is advisable.