Gene×Environment Interactions in Early Externalizing Behaviors: Parental Emotional Support and Socioeconomic Context as Moderators of Genetic Influences?

This study uses longitudinal population-based samples of young siblings to examine the effects of two hypothesized moderators of early externalizing behaviors: parental emotional support and family socioeconomic status. The first sample, a twin sample from the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B), was composed of approximately 600 twin pairs measured on externalizing at ages 4 and 5. Results indicated stronger genetic influences on externalizing at lower levels of parental emotional support but higher levels of socioeconomic status; only the latter interaction remained significant when the two moderators were simultaneously modeled. These moderation effects were not replicated in our analyses of the National Longitudinal Survey of Youth-Child Supplement (CNLSY) data, which contained 1939 pairs of full and half siblings measured on externalizing at ages 4–5 and ages 6–7. Our results highlight the need for replication in quantitative behavior genetics research on externalizing behaviors. Potential causes for non-replication are discussed.