Alterations of biological rhythms are well recognized to play a crucial role in the origin and maintenance of depression, but little is known about the profile of circadian rhythms at a premorbid age in adult depressed patients. The present study was aimed at investigating the association, if any, of depressive disorders with biological and behavioural rhythm modifications both at the time of observation and at an earlier age than the clinical onset of depression. The hypothesis was that such modifications could be an early biological index of vulnerability to the illness.

One hundred and seventy-eight patients affected by DSM-IV Major Depressive Disorder were examined/observed, compared to a group of 178 matched healthy subjects. All the included subjects were asked to fill in a retrospective questionnaire reporting time of awakening and falling asleep and time of subjective peaks of appetite, energy and cognitive function during “Adolescence” (12–15years), “Youth” (16–20years) and “Present condition” periods.

An advance of awakening time by about 20minutes during “Adolescence” was reported in the depressed subjects as compared to the controls. Awakening is also reported as significantly (P<0.001) advanced by about 36minutes during “Youth” in depressed patients, while time of falling asleep at the same age in the patients group shows 19minutes delay. Regarding “Present condition” an advance of awakening time (33minutes) in depressed patients was reported, in association with a delay of the subjective peak of cognitive functioning (62minutes).

Depressed patients show clear-cut differences in sleep pattern as compared to controls, consisting in a constant and significant advance of awakening time, while the time of sleep onset never reaches any statistical difference between the groups throughout ages.

The results are consistent with the hypothesis that early alterations of the general circadian profile can contribute to the onset of adult life Major Depressive Disorders.