Psoralens in association with seasonal affective disorder

The pathogenesis of seasonal affective disorder (SAD) has been attributed to abnormal melatonin metabolism. Perorally administered psoralens increase the daytime levels of melatonin via the competitive inhibition of hepatic melatonin metabolism. Some findings among SAD patients are parallel to those observed after the administration of a psoralen in healthy subjects. It is hypothesized that there may be a circulating psoralen-like substance which affects SAD patients under a low level of illumination. Exposure to bright light during the daylight period would normalize the abnormal effect independently of the season.