An association between high birth weight and schizophrenia in a Finnish schizophrenia family study sample

Longitudinal cohort studies have implicated an association between both low and high birth weight and schizophrenia. It has been suggested that schizophrenia associated genes could augment an individual's susceptibility to adverse prenatal and perinatal environmental events. We investigated the association between birth weight and schizophrenia in a large Finnish schizophrenia family study sample. We utilized the birth weight data of 1051 offspring from 315 Finnish families with at least one offspring with a diagnosis of schizophrenia. We used a multivariate COX frailty model to analyze the effect of birth weight on the risk of developing schizophrenia within the families. Using information from the Medication Reimbursement Register and patient interviews, we further investigated the association of maternal type 2 diabetes and schizophrenia risk among offspring. High birth weight (>4000g) was associated with a 1.68-fold increase in schizophrenia susceptibility. Maternal diabetes at the time of data collection, a proxy for gestational diabetes, was associated with a 1.66-fold increase in the risk of developing schizophrenia among offspring. Our results corroborate recent findings showing an association between high birth weight and schizophrenia. Our results also point to a potential birth-weight independent association between maternal type 2 diabetes and schizophrenia among offspring.