Seasonality of birth in schizophrenia in Taiwan

The phenomenon of seasonality of birth in schizophrenia is important to the study of the etiology of this mental disorder because it helps give directions for further research. Patients' hospital files from 1981 to 1991 at two of the largest hospitals with psychiatric wards in Taiwan were reviewed, and dates of birth were collected on 3,346 patients diagnosed with schizophrenia. After adjusting for the variations of the total monthly births in the population, an Auto-Regressive Integrated Moving Average model was applied. Results support a seasonality phenomenon and indicate a disproportional excess of births in schizophrenia in the cold months (November to February) compared with the hot months (May to August). These findings are compatible with many other studies in other countries and climates. Further investigations of season-related environmental factors in the etiology of schizophrenia are recommended.