The Association between Childhood Maltreatment, Substance Use Frequency, and Physical Intimate Partner Violence: A Gene-Environment Study

This dissertation evaluated the complex inter-relatedness between co-occurring childhood maltreatment exposures, physical intimate partner violence (perpetration and victimization), substance use frequency, and molecular genetics for substance use, utilizing appropriate developmental models and theoretical approaches. Three studies were proposed within this dissertation. Data for the three studies come from a national longitudinal panel study: The National Longitudinal Study of Adolescent to Adult Health (Add Health; Harris, 2013). Across studies, latent profile analysis was used to evaluate co-occurring childhood maltreatment exposures based on type and severity of exposures, which resulted in three homogenous sub-groups. The first sub-group was composed of individuals that had high levels of physical abuse exposure and moderate levels of childhood neglect and emotional abuse exposures (high physical abuse sub-group). The second sub-group (high sexual abuse sub-group) included individuals with high severity of sexual abuse exposure and moderate severity of all other childhood maltreatment types (i.e., physical abuse, emotional abuse, and neglect). This second sub-group was, therefore, the most vulnerable in terms of their childhood maltreatment exposure. A final normative sub-group was also found that included a majority of individuals with low severity of childhood maltreatment exposure across types. Additionally, across all three studies, a probabilistic multifaceted genetic risk score (i.e., polygenic risk score) was created to evaluate substance use related genetic risk. The first study evaluated the role of co-occurring childhood maltreatment exposure on substance use development from adolescence to young adulthood while evaluating substance use related genetic moderation. Generalized estimating equations were used to test the proposed model in study 1. Findings suggest that the high physical abuse sub-group was more susceptible to genetic risk and had increases in substance use frequency only at high levels of genetic risk. In contrast, for the high sexual abuse sub-group, childhood maltreatment and environmental exposures were more ubiquitous for substance use development from adolescence to young adulthood. To elaborate, the high sexual abuse sub-group demonstrated increases in substance use from adolescence to young adulthood irrespective of genetic risk. In study 2, substance use frequency in young adulthood was tested as a mechanism between childhood maltreatment sub-groups and subsequent physical intimate partner violence perpetration in adulthood. Once again, genetic moderation for the direct association between childhood maltreatment sub-groups and substance use frequency in young adulthood was tested within the larger mediation model. In study 3, physical partner violence victimization in young adulthood was tested as a mediator of the association between childhood maltreatment sub-groups and substance use frequency in adulthood. In study 3, in addition to the above-mentioned genetic risk score, an additional substance use related dopamine polygenic risk score was also tested. Specifically, in study 3, genetic moderation by both genetic risk scores was tested on 1) the direct pathway from childhood maltreatment sub-groups to substance use frequency in adulthood, and 2) the direct pathway from physical intimate partner violence victimization in young adulthood to substance use frequency in adulthood. In both studies 2 and 3, product of co-efficient method was used to estimate mediation hypothesis, and moderated-mediation models were used to test for genetic moderation within the mediation model. Research aims for studies 2 and 3 were largely not supported. However, supplementary models indicate that substance use frequency may not be a causal mechanism but may be a contextual factor exacerbating the association between childhood maltreatment exposures and physical intimate partner violence perpetration. Implications for findings are discussed in detail.