Bright white light alleviates depression.

Studies of biological rhythm disorders among manic-depressive patients have suggested that depressed patients may have an early photosensitive interval. If so, exposure to bright light during the photosensitive interval might relieve depressive symptoms. As a test of this hypothesis, 12 depressed patients were exposed to bright white light from roughly 5 to 6 a.m. On the afternoon following this treatment, depressive symptoms were reduced in comparison to baseline ratings and as compared to afternoons following similar exposures to dim red light.