Seasonality in Severity of Depression: Relationships to Suicide and Homicide Occurrence

This 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. 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 and 7 weeks. The analysis show that there is a true seasonality in the severity of illness. (42 refs.)