Effect of light therapy on salivary melatonin in seasonal affective disorder

To investigate the role of a light-induced advance in the timing of the melatonin rhythm in seasonal affective disorder, 11 depressed patients underwent 2 weeks of light therapy with full spectrum or cool white light. Evening saliva samples were collected before and after each week of treatment and assayed for melatonin to determine the time of onset of nocturnal secretion. Both treatments reduced depression scores, advanced the timing of the melatonin rhythm, and increased melatonin concentrations. Time of onset of the nocturnal increase in melatonin did not differ between clinical responders and nonresponders, suggesting that a phase advance in the onset of nocturnal melatonin secretion is not sufficient to induce clinical remission in seasonal affective disorder.