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Some previous studies have reported seasonal or monthly variations in the occurrence of depressive syndromes. The present study was carried out in order to investigate seasonality in severity of depression. Toward this end, the authors measured the Zung Self-Rating Depression (ZD) and Anxiety (ZA) Scales scores in 104 consecutively admitted depressed patients between November 1983 and April 1985. The data were analyzed by means of spectral analysis of a single time series. Up to 47.9% of the variance in the weekly average of the ZD scores could be explained by two significant rhythms of 51 (circannual) and 7 weeks. Peaks in ZD scores were observed in April-May, with lows occurring in August-September. Up to 30.8% of the variance in the weekly average of ZA scores was explained by a circannual rhythm. Our results show that there is a true seasonality in the severity of illness of depressed subjects. There were significant correlations between the weekly average in severity of illness and the chronograms of suicide (positively) and homicide (negatively) occurrence in Belgium.

Objective: Previous studies have reported seasonal or monthly variation in suicide. The present study was conducted in order to determine seasonality and other significant rhythms in violent and nonviolent suicide, alone and together, and homicide., Method: Data on suicide, violent suicide, nonviolent suicide, and homicide (categorized according to ICD-9) for all of Belgium for the period 1979-1987 were analyzed by means of spectral analyses., Results: There was a significant seasonality for suicide but not homicide. Seasonality was present in violent but not in nonviolent suicide. The number of violent suicides increased with age and was more prominent in men. The violent suicide chronograms of younger and elderly persons were quite distinct in the occurrence of peaks in March-April and August, respectively, and lows in December-January. There was no significant relationship between violent suicide and homicide., Conclusions: Seasonality in suicide is determined by significant circannual rhythms in violent suicides, which differ between younger and elderly persons.