Kripke D F, Risch S C, Janowsky D
Psychiatry Res. 1983 Oct;10(2):105-12. doi: 10.1016/0165-1781(83)90109-9.
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.
