Background. Urban birth is associated with later schizophrenia.
study examined whether this
finding is diagnosis-specific and which individuals are most at risk.
Methods. All live births recorded between 1942 and 1978 in
any of the 646 Dutch municipalities
were followed-up through the National Psychiatric Case Register for
first psychiatric admission for
psychosis between 1970 and 1992 (N=42115).
Results. Urban birth was linearly associated with later
schizophrenia (incidence rate ratio linear
trend (IRR), 1·39; 95% confidence interval (95% CI), 1·36–1·42),
affective psychosis (IRR, 1·18;
95% CI, 1·15–1·21) and other psychosis (IRR, 1·27;
1·24–1·30). Individuals born in the
highest category of the three-level urban exposure were around twice as
likely to develop
schizophrenia. Associations were stronger for men and for individuals
with early age of onset. The
effect of urban birth was also stronger in the more recent birth cohorts.
Conclusions. There are quantitative differences between
diagnostic categories in the strength of the
association between urban birth and later psychiatric disorder. High
rates of psychosis in urban
areas may be the result of environmental factors associated with urbanization,
the effect of which appears to be increasing over successive generations.