Entrainment and Masking in the Chronobiology of Depression

Abstract

In order to analyse the possible role of the main circadian pacemaker (1) in endogenous depression (2), a large scale chronobiological investigation has been performed by an interdisciplinary research group at our institute. 20 inpatients with the RDC-diagnosis of major depressive disorder, endogenous subtype, 10 of whom could be reinvestigated after, at least almost, complete clinical remission, and 10 healthy probands of similar sex- and age distribution were included in the study. All subjects had been drug free for usually at least one week prior to the onset of an observation period of at least two weeks and were, with only one exception, not medicated before the termination of it. During this time period night sleep was recorded polygraphically (cf. H. Schulz et al. in this volume), and a series of equidistant measurements was taken six times every day from 7:00 a.m. to 10:00 p.m. and once every night at 2:30 a.m. Several of the investigated variables were regarded as reflecting, more or less directly, the degree of severity of depression (three mood scales, a self-assessment of daily activities, two measures of spontaneous motor activity, a motor speed test and a calculation test). The other variables, although conceived as possibly being related to the severity of depression, were primarily selected as indicators of the function of the main circadian pacemaker, i. e. salivation rate, urine volume and urinary excretion of sodium, potassium and free cortisol, and, furthermore, core body temperature which, at night, was recorded continuously by a rectal probe. In addition, also room temperature and humidity were measured at the times of the subjects’s assessments.