Toddler risk and protective characteristics: Common and unique genetic and environmental influences

The goal of this study was to disentangle the common and unique genetic and environmental influences on social–emotional competence, problem behavior, physiological dysregulation, and negative emotionality (NE) in toddlers. The sample consisted of 243 twin pairs (mean age =31.94 months) rated by primary caregivers (>95% mothers) on the Children's Behavior Questionnaire and the Infant-Toddler Social and Emotional Assessment. A multivariate Cholesky Decomposition revealed three shared environmental factors, with one set of environmental influences common to competence, problem behavior, and physiological dysregulation, a second common to problem behavior and physiological dysregulation, and a third common to physiological dysregulation and NE. Also, there were two additive genetic factors, with one explaining variance in competence, NE, and a small amount of variance in problem behavior, and a second explaining variance in problem behavior and NE. Given the common shared environmental factors across outcomes, these results suggest that toddlerhood could be a particularly important time to intervene, as interventions could simultaneously improve competencies and reduce problem behaviors. This study also highlights the need for genetically informed research to examine the etiology of multiple outcomes and address overlap.