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Title page for ETD etd-11182015-210720

Type of Document Master's Thesis
Author Zhu, Joyce Yueyue
URN etd-11182015-210720
Title Conscientiousness and Grit associated with Depressive Symptoms: Phenotypic and Heritability Analyses of a Twin Sample
Degree Master of Science
Department Psychology
Advisory Committee
Advisor Name Title
David H. Zald Committee Chair
Bunmi O. Olatunji Committee Member
Leslie D. Kirby Committee Member
Steven D. Hollon Committee Member
  • achievement
  • personality
  • depression
  • behavior genetics
  • motivation
Date of Defense 2015-04-29
Availability unrestricted
Current theories of the relationship between personality and depression largely ignore conscientiousness and grit, leaving little conceptual framework for investigation. Among the handful of studies having investigated such relations, few have identified personality-depression explanatory models for conscientiousness and grit. Thus, this thesis investigates the relationships from the theoretical perspective of motivation-related attribution theory using classical theories of achievement motivation and learned helplessness (reformulated). To gain insight into the types of personality-depression explanatory models (e.g. common cause, vulnerability, etc) with which grit and conscientiousness are most consistent, this thesis investigates phenotypic correlations with depressive symptoms and shared genetic influences at both domain and facet-levels of analyses. The study examined a sample of 248 individuals, which included 106 complete twin pairs (MZ = 56; DZ = 50). Findings reveal previously unexplored facet-level relations between grit and depressive symptoms, while uncovering a previously unreported association between the conscientiousness facet, Deliberation, with depressive symptoms. Novel findings include shared genetic variance with depressive symptoms for Perseverance of Effort facet of grit, and Competence facet of conscientiousness, implicating the common cause model. Further, comparing relative contributions of Grit and Conscientiousness with depressive symptoms uncovered unique shared genetic influences with depressive symptoms, suggesting differential effects not apparent in phenotypic analyses. Limitations and future directions are discussed.
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