Prophylactic treatment of seasonal affective disorder (SAD) by using lightvisors: Bright white or infrared light?

Background: Thirty-eight patients with SAD participated in a light visor st udy addressing two questions. 1. Can the development of a depressive episode be prevent ed by daily expos ure to bright light started before symptom onset in early fall and continue d throughout the winter? 2. Does the light have to be visible in order to have beneficial effects' Methods: Three groups participated in rite study: I (n 14) received bright white light (2500 lux); II, (n = 15) received infrared light (0.18 lux); II I (n = 9, control group) did not receive any light treatment at all. Results: Infrared light is just as effective as bright white light. Both ar e more effective than the control condition. Conclusions: Light visors can be effectively used to prevent the developmen t of SAD, The fact that exposure to infrared light was as effective as expo sure to bright white light questions the specific role of visible light in the treatment of SAD. (C) 1999 Society of Biological Psychiatry.