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.