An association between both low and high birth weight and increased disorganized and negative symptom severity in schizophrenia and other psychoses

Longitudinal cohort studies have implicated an association between both low and high birth weight and increased schizophrenia risk. In this study, we investigated the effect of birth weight on the symptom severity of psychotic disorders including schizophrenia in a Finnish schizophrenia family study sample. We used a multivariate GEE (General Estimating Equation) regression model to investigate the association of birth weight and symptom severity in 282 subjects with a primary psychotic disorder, 178 of whom had a diagnosis of schizophrenia. The Scales for the Assessment of Positive and Negative Symptoms (SAPS and SANS) were used as a measure of symptom severity. Sex, place of birth and year of birth were adjusted for in the model. Both low and high birth weight were associated with more severe symptoms with respect to bizarre behaviour, affective flattening and attentional impairment. In addition, low birth weight was associated with more severe symptoms with respect to positive formal thought. Our findings suggest that both low and high birth weight can influence the symptom severity of psychotic disorders. Our results implicate an association between both low and high birth weight and disorganized and negative symptoms.