The influence of phototherapy on serotonin and melatonin in non-seasonal depression.

Circadian profiles of melatonin in serum and serotonin in blood were assessed before and after 7 days of artificial light treatment in 30 patients with non-seasonal depression and 12 healthy subjects. Patients and volunteers were allocated at random to either dim (50 lux) or bright light (2,500 lux) for 2 hours daily. The study has not been completed yet. Preliminary findings are presented here. Light treatment modifies marginally the circadian melatonin profiles of depressed patients and healthy subjects; however, it augments blood serotonin throughout the day. This increase is seen in all patients and healthy subjects after bright as well as dim light. These results suggest that the influence of light is more pronounced on serotonin than melatonin metabolism.