Unintentional injuries in a twin study of preschool children: environmental, not genetic, risk factors

To analyze the relative contribution of latent genetic and environmental factors to differences in the injury liability of children, and to examine the association between measured socio-economic, family, and child-behavior variables and unintentional injury risk.

Unintentional injuries from birth to age 5, together with information regarding measured risk variables, were reported by mothers in a sample of 1027 same-sex twin pairs from a nationally representative 1994-1995 birth cohort.

Child-specific environmental factors accounted for most of the variance (86.4%) in the likelihood of ever having an injury. When considering the risk of two or more injuries child-specific environmental factors explained 60.2% of the variance and family-wide environmental influence 39.8%. Measured socio-economic, family, and child-behavior factors predicted frequent injury.

Results give little support to the concept of a heritable injury-prone trait in preschool children; environmental influences accounted for most of the injury variance in this sample. However, behavioral variables, especially the child's externalizing problem behaviors, are also important in explaining unintentional injuries.