Body size and violent offending among males in the Northern Finland 1966 birth cohort

Background Childhood onset aggressive behavior is one of the most stable human characteristics. Previous literature indicates that this behavioral trait may be associated with body size. The present study investigated the association between body sizes at different ages and committing violent crimes in adulthood. Methods The Northern Finland 1966 Birth Cohort includes 5636 males followed up to age 31 years prospectively. Information on criminality was extracted from official records. Body sizes were measured at birth, 12 months and 14 years of age, and compared the violent and the non-violent offenders with the non-offenders. Optimal cut-off points for each of the body size measures for the differentiation of the three groups were identified. Odds ratios were adjusted taking account of maternal age, socioeconomic status of the family of origin, mother's marital status, parity, smoking during pregnancy, gestational age and unwanted pregnancy. Results Both high body mass index (BMI) and small head circumference at 12 months were associated with increased risk of violent offending (adjusted ORs 1.6-1.8). High BMI at 12 months combined with small head circumference was associated with substantially increased risk of violent offending (OR 4.2, 95% CI 2.6-6.8). Conclusions In males, small head circumference and large body size at 12 months of age were strongly associated with an increased risk of violent, but not non-violent offending in adulthood. The measures at 12 months were the strongest predictors, suggesting that this association may be explained by genetic or early environmental factors, rather than social learning later in childhood and adolescence.