Height, weight and body mass index in early adulthood and risk of schizophrenia

OBJECTIVE: To illuminate the possible associations between height, weight, and body mass index (BMI) during early adulthood and the development of schizophrenia. METHOD: This prospective study is based on an all-male sample of 3210 individuals from the Copenhagen Perinatal Cohort, comprising individuals born between 1959 and 1961. In 1999, cases of schizophrenia were identified in the Danish Psychiatric Central Register, and the cases were compared with the cohort pool of controls with respect to height, weight, and BMI from draft records. The effect of low BMI was adjusted for parental social status when the cohort members were 1 year old, birth weight, birth length, and maternal pre-pregnancy BMI. RESULTS: Forty-five cases of schizophrenia had a lower young adult mean body weight and BMI than controls. A significant inverse relationship between BMI and risk of later schizophrenia was found. For each unit increase in BMI, the adjusted odds ratio was 0.81 (95% CI, 0.70-0.93) and the risk of schizophrenia decreased by 19%. Excluding individuals who had been admitted to an in-patient facility before or within 5 years after appearing before the draft board, yielded virtually the same results. No significant differences between cases and controls were observed with respect to adult height. CONCLUSION: Independent of several possible confounders, an inverse relationship between young adult BMI and risk of later development of schizophrenia was demonstrated in this all-male sample.