BackgroundLow birth weight has been postulated to be a risk factor for schizophrenia.MethodObstetric history, premorbid adjustment, and cognitive function during admission were assessed in 167 patients with DSM–III schizophrenia or affective psychosis.ResultsA birth weight of less than 2500 g was significantly more common in patients with schizophrenia than in those with affective psychosis. Schizophrenic patients as a group had significantly lower mean birth weight, a finding which was particularly marked after controlling for sociodemographic confounders. In schizophrenic men, lower birth weight was highly significantly correlated with poorer premorbid social and cognitive ability, and with impairment of adult cognitive function.ConclusionsNeurodevelopmental impairment may cause poor foetal growth, and schizophrenia in adult life.