A randomized, placebo-controlled trial of bright light and high-density negative air ions for treatment of Seasonal Affective Disorder.

This study, conducted over the course of 5 years, assessed the antidepressant efficacy of two active treatments, bright white light and high-density negative ions, and the efficacy of two placebo treatments, dim red light and low-density negative ions, for Seasonal Affective Disorder (SAD). In a controlled laboratory setting, 73 women with SAD were exposed to one of the four treatment conditions over 12 consecutive days. Pretreatment expectation ratings did not significantly differ among the four treatment groups; however, expectation scores and treatment benefits were positively related. Over the course of treatment, subjects in all four groups showed significant score decreases on the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder Version-Self Rating (SIGH-SAD-SR) and on the Beck Depression Inventory (BDI). For raw scale scores, neither main effects of treatment nor interactions between treatment and time were significant. When remission outcome criteria were used, bright white light was significantly more effective than any of the other three treatments, and exposure to high-density negative ions was more effective than either of the two placebo conditions, although the difference was not significant.