Treatment of bipolar disorder often results in patients taking several drugs in an attempt to alleviate residual depressive symptoms, which can lead to an accumulation of side effects. New treatments for bipolar depression that do not increase the side effect burden are needed. One nonpharmacological treatment with few side effects, bright light therapy, has been shown to be an effective therapy for seasonal affective disorder, yet has not been extensively studied for other forms of depression. Forty-four adults with bipolar disorder, depressed phase were randomized to treatment with bright light therapy, low-density or high-density negative ion generator for 8 weeks. The primary measure of efficacy was the Structured Interview Guide for the Hamilton Depression Rating Scale with Atypical Depression Supplement (SIGH-ADS). Adverse events were assessed using the Young Mania Rating Scale (YMRS) and Systematic Assessment for Treatment Emergent effects (SAFTEE). All outcome variables were statistically analyzed using a mixed model repeated measure analysis of variance (ANOVA). The results showed no statistically significant differences between groups in any outcome measures at study end point; adverse events, including switches into hypomania, were rare. Further research is needed to determine the efficacy of bright light therapy in this population. (C) 2012 Elsevier Ireland Ltd. All rights reserved.