To investigate the role of chronobiological disorders in the pathogenesis of insomnia in case of depression.

38 patients have been studied (F 31.3 - 31.4, F 32.0 - 32.2, F 33.0 - 33.2). Severity of depression was determined in accordance with HAMD-17. The patients have been divided into two groups: group 1 (HAM-D: insomnia early + insomnia middle + insomnia late - 0-4) - 10 patients (HAM-D - 27.5±4.2) and group 2 (HAM-D: insomnia early + insomnia middle + insomnia late - 5-6) - 28 patients (HAM-D - 31.7±5.9). The spectral analysis of heart rate variability was applied. The power spectrum density of LF (low frequency) and HF (high frequency) range was established. The patients were examined at 1 a.m., 7 a.m., 1 p.m., 7 p.m. prior to the beginning of treatment.

Prior to the therapy de-synchronization of the circadian rhythms of the parameters of spectral analysis of heart rate variability and the “sleep-wake” rhythm has been observed. This manifested itself in the shift of the phase of the circadian rhythms of the parameters under study towards the earlier time of the day. The phase shift to an earlier time was more pronounced in group 1.

Insomnia in severe depression may depend rather on the usual nocturnal hour position change after phase displacement in the circadian curve, than on the severity of de-synchronization of circadian rhythms. In these hours the change (increase or decrease) of sympathic/parasympathic activity may be of greater importance.