[Diurnal variations of symptoms of depression]

New symptom-statistical, chronobiological and experimental investigations concerning diurnal variation in endogenous depression (melancholia) are reported and interpreted referring to psychopathological, biological and phenomenological aspects. According to recent studies, the so-called typical diurnal variation of mood (with morning low) is not as frequent, as it was assumed before, and even intraindividually unstable. Although more frequent than other daily rhythmus, the so called typical diurnal variation should not be used for diagnostic purposes, because it is quite frequent in different depressive states as well. During their healthy intervals endogenous depressive patients show not rarely an analogous diurnal variation of mood; this was also found in healthy subjects. Therefore the so called typical variation in mood is not specific, and it is questionable whether it is a marker of endogenous depression at all. Concerning circadian rhythm biological functions were examined more often than the depressive symptomatology itself (especially temperature, heart rate, cortisol and other neuroendocrine parameters). Unexpectedly there were only slight variations of the circadian diurnal curves in melancholic patients compared to healthy subjects. The circadian rhythm in endogenous depression does not seem to be very different from the physiological diurnal course. Comparing the biological circadian curves in endogenous depression to the curves of the depression symptomatology, the similarities outline the differences. Sleep research didn't show any results, supporting the suggestion of a specific rhythm variation either. Therefore the opinion, that the circadian rhythm is altered basically in melancholia, cannot be maintained, neither psychopathologically nor biologically. Experiments of time estimation in the course of the day could'nt explain the diurnal variation in mood either.