[Circadian rhythms of the central temperature and blood cortisol in endogenous depression]

Beside neurochemical imbalances, there are numerous disruptions of circadian rhythms in endogenous depression. Recent studies have actually shown instability in rhythmicity and phase advance of many circadian rhythms in depression (central temperature, cortisol, urinary MHPG...). We have observed the longitudinal evolution of circadian rhythms (core temperature, plasma cortisol) of depressed patients who were treated by a two weeks phase-advance process, then with antidepressant drugs. Our results show that clinical improvement during phase-advance process is much faster than under tricyclics, with the same Hamilton scale level after two weeks of treatment. From a biological point of view, we show an ultradian instability, a phase advance (2 to 4 hours) and modifications of averages and amplitudes of circadian rhythms. These abnormalities tend to disappear during phase-advance process and antidepressant therapy. Phase response curves to the phase shift in depressed patients could be explained by a bad sensitivity of these subjects to external synchronisers linked to an internal dyschronism. These disturbances lead us to link desynchronisation and endogenous depression.