Melatonin levels in drug-free patients with major depression from the southern hemisphere Livia A. Carvalho a, * , Clarice Gorenstein b , Ricardo A. Moreno c , Regina P. Markus a a Department of Physiology, Institute of Biosciences, Universidade de Sa˜o Paulo, Rua do Mata˜o, travessa 14 sala 323, CEP 05508-900Sa˜o Paulo, SP, Brazil b Laboratory of Medical Investigation-23, Psychopharmacology, Department of Pharmacology, Institute of Biomedical Sciences, Institute of Psychiatry, Universidade de Sa ˜o Paulo, HC-FMUSP, Rua Dr Ovı ´dio Pires de Campos, 785, Te ´rreo, CEP 05403-010Sa˜o Paulo, SP, Brazil c GRUDA—Grupo de Estudos de Doenc ¸as Afetivas, Institute of Psychiatry, HC-FMUSP, Dr Ovı ´dio Pires de Campos, 225, Pre ´dio da Administrac ¸a˜o, Andar M, sala 03, CEP 05403-010 Sa ˜o Paulo, SP, Brazil Received 12 August 2005; received in revised form 28 February 2006; accepted 28 February 2006 KEYWORDS Melatonin; 6-Sulphatoxy- melatonin; Major depression; Healthy volunteers; Southern hemisphere; Human Summary The secretion of melatonin has been shown as abnormal in some depressed patients, but most such studies were conducted in the northern hemisphere and with severely depressed inpatients. The aim of this study was to evaluate melatonin excretion profiles in major depressive outpatients from Sa˜o Paulo, Brazil, individually matched to well-screened healthy volunteers to examine whether melatonin abnormalities are also present in patients from the southern hemisphere, and in less severely ill patients. We analyzed 32 drug-free, depressed outpatients and 32 psychiatrically healthy volunteers matched for age and gender. We also examined a set of 15 drug-free depressed outpatients and 15 healthy volunteers that were matched not only for age and gender, but also for body mass index and season, all factors known to influence melatonin excretion in humans. All patients fulfilled DSM-IV criteria for major depression. We evaluated major urinary metabolite of melatonin, 6-sulphatoxymelatonin (aMT6s), produced over 24 h and divided into four periods (06:00–12:00, 12:00–08:00, 18:00–24:00 and 24:00–06:00 h). aMT6s measurements during the 24 and 6 h intervals were similar in the 32 depressed patients and 32 healthy volunteers matched for age and gender; further matching for body mass index and season did not alter the results. Our study supports others in which depressed patients were found to have similar melatonin levels than healthy volunteers. Melatonin excretion has been considered a physiological index for noradrenergic function, which in some studies were found to be altered than depressed patients. It is conceivable that the alteration of nocturnal melatonin in Psychoneuroendocrinology (2006) 31, 761–768 www.elsevier.com/locate/psyneuen 0306-4530/$ - see front matter Q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.psyneuen.2006.02.010 * Corresponding author. Address: Division of Psychological Medicine, Section of Clinical Neuropharmacology, Stress, Psychiatry and Immunology Laboratory (SPI-Lab), King’s College London, PO51, Institute of Psychiatry, 1 Windsor Walk, Room 103, London SE5 8AF, UK. Tel.: C44 20 7848 0352; fax: C44 20 7848 0051. E-mail address: l.carvalho@iop.kcl.ac.uk (L.A. Carvalho).