Childhood central nervous system infections and risk for schizophrenia.

Central nervous system (CNS) viral infections have been suggested to increase the risk of schizophrenia, although most of the evidence is indirect and comes from rather few studies on exposure to various infections in general. In the Northern Finland 1966 Birth Cohort the association between schizophrenia and other psychoses and childhood CNS infections has been analysed, and in this paper we present the follow-up results up to the end of 1994 and 1997. Data regarding the infections were collected prospectively between 1966-1980 and data on psychoses from 1982. The registered psychiatric diagnoses were validated using the DSM-III-R classification. Out of the 11017 subjects (96% of all births in that year) 145 had suffered a CNS infection during childhood, which in 102 cases was a viral infection. In the follow-up to the end of 1994, 76 had schizophrenia, and their number increased to 100 to the end of 1997. In addition, up to the end of 1994, 52 patients had a non-schizophrenic psychosis. Four cases in the schizophrenia patient group and none of the patients with other psychosis had suffered a viral CNS infection. None of the schizophrenia cases and two of the patients with other psychosis had had a bacterial infection. The adjusted odds ratio for schizophrenia after a viral CNS infection was 4.8 (95% confidence intervals [CI] 1.6-14.0) in the follow-up to the end of 1994 and 2.5 (0.9-7.0) in the follow-up to the end of 1997. The clinical course variables did not differ between the schizophrenia patients with or without CNS infection. Our results suggest that viral CNS infections during childhood may have a role as a risk factor for schizophrenia. Their role may be modest at the population level due to their relative rareness.