Melatonin in relation to body measures, sex, age, season and the use of drugs in patients with major affective disorders and healthy subjects.

Serum melatonin levels over a 24 hr period were studied in 30 acutely ill patients with major depressive episode, 24 patients with a history of unipolar or bipolar major affective disorder in remission and 33 healthy subjects. A significant negative correlation (-0.45) between body height and maximum nocturnal serum melatonin level was found. Maximum serum melatonin levels during the night were lower in both patient groups than in the healthy controls. No difference was found between maximum nocturnal serum melatonin levels in 26 patients investigated when ill and again in remission. We thus propose low nocturnal melatonin to be a trait-dependent marker for major depressive disorder. A difference in the morning but not night melatonin levels was found between samples taken during the dark, winter season versus samples taken during the bright, spring-summer season. Melatonin levels were not lower in females than in males, when melatonin levels were adjusted for body height. Similar results were found when the nocturnal areas under the curve for melatonin were analyzed.