Melatonin in light treatment of patients with seasonal and nonseasonal depression

Melatonin as a marker of circadian rhythm and the effect of bright light on melatonin were studied in 63 depressed patients, 42 with a seasonal pattern and 21 with a nonseasonal pattern. The patients were matched for age, time of treatment and severity of depression. Before light treatment, blood was sampled for melatonin and depression was clinically rated with the Comprehensive Psychopathological Rating Scale and Hamilton Depression Rating Scale. Two hours of light treatment, 350 cd/m 2 , was given daily for 10 days 0600 to 0800 or 1800 to 2000. Of the 42 patients with seasonal depression, 26 were treated with morning light and, 16 with evening light. The melatonin amplitude was significantly decreased by light, and the melatonin phase position was advanced by morning light and delayed by evening light. All patients except for 3 in each group changed in the expected direction. Although the patients with seasonal pattern had a more favorable outcome than patients with nonseasonal pattern, there was no difference in therapeutic outcome related to the baseline melatonin phase position. The hypothesis that the short term clinical effects of light therapy either in the morning or evening are related to pretreatment melatonin levels or alteration of melatonin amplitude or phase position was not supported in the study. There was also no significant difference between the seasonal and nonseasonal patients related to the degree of light suppression of melatonin or the rebound effect of serum melatonin levels following bright light exposure between 2200 and 2300 before regular light treatment.