| dc.description.abstract | 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. | |
