Seasonality of first admissions for schizophrenia in the Southern Hemisphere

Northern Hemisphere studies of first admissions for schizophrenia have show n an excess of summer admissions (June, July and August) compared to other times of the year. The within-year fluctuations in first admissions could b e related to meteorological factors that fluctuate between seasons (e.g. te mperature, photoperiod) and/or social factors (e.g. holidays, religious eve nts). If meteorological factors were primarily responsible for the fluctuat ion, then Southern Hemisphere studies should find excess first admissions i n December, January and February. This paper presents the first season of f irst admission study of schizophrenia in the Southern Hemisphere. The month and year of first admission for schizophrenia (ICD 8/9) for 4487 male and 3252 female, Australian-born individuals were extracted from a Queensland m ental health register. Spectral analysis showed a strong annual periodicity of first admissions for males with the peak in August (Southern Hemisphere winter) and a trough in the summer months (December to February). The patt ern for females also displayed annual periodicity. These results correspond to the Northern Hemisphere reports of excess of schizophrenia first admiss ions in terms of the month of the year but not the season of excess. Furthe r work is needed in order to clarify the impact of latitude and meteorologi cal factors on the month of first admission for schizophrenia. (C) 2000 Els evier Science B.V. All rights reserved.