The daily course of the symptomatology and the impaired time estimation in endogenous depression (melancholia).

The importance of 'typical' diurnal variations in mood (depression worse in the morning) as a diagnostic criterion of endogenous depression has been challenged in previous investigations. Disturbance in time experience may contribute towards an understanding of diurnal variation in depressive symptomatology. To examine this hypothesis a series of time estimation experiments was conducted in the course of the day. Twenty-five endogenous depressive patients (according to ICD-9) and 12 healthy controls were asked to estimate prospectively a 30-s interval on two successive days at 7.30 a.m., 11.30 a.m., 3.30 p.m. and 7.30 p.m. Simultaneously the subjects assessed their state of well-being using a visual analogue mood scale. A circadian rhythm of time estimation errors could not be detected; even in daily courses with 'typical' diurnal variations an increasingly favourable self-assessment of well-being was not accompanied by a corresponding diurnal fluctuation of time estimation. These results cast additional doubts on the significance of 'typical' diurnal variations in depressive symptomatology.