ANTIDEPRESSANT EFFECT OF 5-METHOXYPSORALEN - THE MELATONIN SYNCHRONIZER HYPOTHESIS

5-methoxypsoralen (5-MOP) stimulates pineal melatonin secretion, and a decrease in dark phase melatonin levels has been described in major d epression. As exogenous melatonin has shown synchronizer properties, a uthors hypothesized that giving 5-MOP would have antidepressant proper ties. Twenty-six inpatients meeting the criteria of major depressive d isorders were enrolled in a four-week, double blind trial of 5-MOP ver sus amitriptyline. Clinical improvement was identical in both treatmen t groups but biological changes were different in each group: 5-MOP pa tients showed an early nocturnal surge of melatonin levels that was ma intained at the fourth treatment week, while melatonin levels remained unchanged in patients treated with amitriptyline.