Seasonality prevalence and incidence of depressive disorder in a general practice sample: identifying differences in timing by caseness.

A total of 2225 consecutive consulting general practice patients attending a North London Health Centre over the course of a year were screened and interviewed for the presence of psychiatric disorder using the GHQ and SADS; 196 patients suffering from RDC depressive disorders were identified and followed up for a further 12 months. A difference in prevalence incidence and recovery time was identified between major and minor depression. Various associations between season of onset and a range of variables were observed. Logistic modelling identified interactions between some of these variables some of which have not been explored in previous studies.