a1 Department of Psychiatry, Institute of Psychiatry, King's College London, London, UK
a2 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
Background There is abundant evidence that schizophrenia is associated with cognitive deficits in childhood. However, previous studies investigating school performance have been inconclusive. Furthermore, there are several biological and social factors that could confound the association. We investigated whether school performance at age 16 is associated with risk of adult schizophrenia and other psychoses in a large national cohort, while controlling for multiple confounders.
Method Using a national sample of 907 011 individuals born in Sweden between 1973 and 1983, we used Cox regression to assess whether scholastic achievement at age 15–16 predicted hospital admission for psychosis between ages 17 and 31, adjusting for potential confounders.
Results Poor school performance was associated with increased rates of schizophrenia [hazard ratio (HR) 3.9, 95% confidence interval (CI) 2.8–5.3], schizo-affective disorder (HR 4.2, 95% CI 1.9–9.1) and other psychoses (HR 3.0, 95% CI 2.3–4.0). Receiving the lowest (E) grade was significantly associated with risk for schizophrenia and other psychoses in every school subject. There was no evidence of confounding by migrant status, low birthweight, hypoxia, parental education level or socio-economic group.
Conclusions Poor school performance across all domains is strongly associated with risk for schizophrenia and other psychoses.
(Received June 11 2006)
(Revised September 19 2007)
(Accepted September 24 2007)
(Online publication November 08 2007)