[Seasonality of birth in schizophrenia patients. Literature review]

Schizophrenia is a major public health problem. The paper presents a review of the literature about seasonality of birth in schizophrenia. Tramer (1929) reported the first study on seasonality of birth in mental disorders. Seasonality of the birth of people who develop schizophrenia refers to a 5-8% excess of births in winter months. However, the peak of research into this phenomenon started in the 1990's. Torrey et al. (1997) reviewed over 250 studies from 29 countries in the Northern Hemisphere and 5 publications by authors from the Southern Hemisphere, concerning the relationship between birth seasonality and the incidence of schizophrenia. The research findings from the Northern Hemisphere were consistent, indicating a 5-8% increase in the risk for mental disorders in individuals born between December and May. Meta-analysis of investigations from the Northern Hemisphere indicates that seasonality of birth increases with geographical width. Results of research from other geographical areas, analysis of stability of this phenomenon during decades and attempts of explanation of seasonality are presented.