Gasperi, Marianna2016-04-142016-04-142013-11https://hdl.handle.net/11299/178963University of Minnesota Ph.D. dissertation.November 2013. Major: Psychology. Advisors: William Iacono, Matt McGue. 1 computer file (PDF); vii, 113 pages.Objective: While childhood maltreatment (CM) and psychopathology are strongly associated, the causality of their relationship is unclear. Existent research has interpreted the maltreatment effect as a causal one, where by CM increases the risk of subsequent psychopathology. In two studies, this dissertation explores the relationship between CM and externalizing psychopathology (EXT), and CM and Major Depressive Disorder (MDD). Methods: A co-twin control method, utilizing 1382 pairs of twins from two cohorts of the Minnesota Twin Family Study, was used to compare the difference in adult psychopathology symptoms between CM-positive, and CM-negative twins. MZ twins who are discordant for exposure provide a model (assumed to control for genetics and shared environment) allowing for the direct estimation of the effect of CM within discordant twin pairs. Models were fit to the twin data and study hypotheses were tested using mixed-level regression using SAS Proc Mixed (Littell, 1996). Results: Consistent group differences on level of psychopathology across maltreatment for both males and females were confirmed. The relationship between CM and psychopathology does not appear generally causal but instead reflects a combination of genetic and environmental confounding effects. The patterns of genetic influence vary across disorders. Conclusion: The results confirm the association between CM and psychopathology, but emphasize the significance of genetic mediation on the relationship in both the externalizing domain and MDD. These results challenge the belief that CM directly contributes to psychopathology. Further research into the mechanism underlying this genetic confounding is discussed.enThesis or Dissertation