The genetic etiology of inhibitory control and behavior problems at 24 months of age

Background:  To investigate links between inhibitory control (IC) and behavior problems in early childhood, as well as genetic and environmental covariances between these two constructs. Methods:  Parent and laboratory ratings of IC and parent ratings of externalizing and attention deficit hyperactivity disorder behaviors were administered at 24 months of age on a sample of 291 same‐sex twin pairs (131 monozygotic, 160 dizygotic). Results:  There were significant phenotypic associations between both IC assessments and the two areas of behavioral maladjustment (correlations ranged from −.13 to −.57). Multivariate analyses revealed that phenotypic covariance between IC and behavior problems could be substantially explained by common genetic influences (genetic correlations ranged from −.30 to −.74). Parent ratings of IC showed higher phenotypic and genetic correlations with behavior problems than lab ratings of IC. Conclusions:  This study is the first to examine the etiology of the covariance between IC and related behavioral difficulties in toddlerhood. Findings suggest that low levels of IC can be considered a genetic risk factor for the development of early emerging behavior problems.