Genetic and home chaos influences in early childhood have been independently associated with externalizing problems, characterized by inattentive, hyperactive, and aggressive behaviors. However, the Behavioral Genetics approach indicates that genetic and environmental influences, although independently effective, interact to produce behavior throughout development. Thus, this thesis uses two samples, the Early Growth and Development study (EGDS), n= 564, and the Avon Longitudinal Study of Parents and Children (ALSPAC), n= 8,952, and two genetically-sensitive approaches, a parent-child adoption approach and a polygenic scoring approach, to examine how genetic influences and home chaos interact in early childhood (age 3-4) to predict externalizing problems later in childhood (age 7). Results indicate that, although home chaos is correlated with later externalizing problems, the effect is reduced in the context of earlier externalizing, possibly suggesting that home chaos is most salient for concurrent, not later, externalizing problems. In addition, genetic influences were not predictive of externalizing problems in either study, nor was the interaction of home chaos and genetic influences. This pattern of results suggests that, although home chaos may be an important factor for concurrent externalizing problems, other factors, e.g., parenting style and prenatal risk, may be more salient than home chaos, especially in interaction with genetic effects. Further, failure to find genetic influence in this thesis suggest that accounting for the broad scope of genetic influences on complex traits like externalizing and the specific genetic risk for individual externalizing phenotypes is important in attempts to find genetic influence and interaction.

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