Bair, Jessica2021-10-132021-10-132021-08https://hdl.handle.net/11299/224926University of Minnesota Ph.D. dissertation. 2021. Major: Psychology. Advisor: William Iacono. 1 computer file (PDF); vi, 161 pages.There are two overarching themes of this dissertation. The first is to evaluate the robustness of unique relationships between nonacute cannabis use occurring across adolescence and young adulthood and young adult cognitive outcomes. The second is to explore possible alternative explanations for associations found and separate potential causal influences of cannabis on cognition from shared familial or environmental factors. Research in this area has predominantly relied upon cross-sectional studies, and critics have raised concerns regarding the impact of extraneous factors insufficiently addressed within research, leaving the true relationship between cannabis and cognition uncertain. To address this and other limitations in the literature, this dissertation was designed to examine the relationship between cannabis use across adolescence and young adulthood and young adult cognitive outcomes. We used a large population-based twin sample with longitudinal tracking of cannabis use along with extensive neuropsychological assessment and interviewing and a quasi-experimental research design to draw stronger causal inferences. Across the two studies, nonacute cannabis use was associated with deficits in neurocognitive outcomes. Study 1 highlighted the importance of controlling for confounding as many of the associations did not survive covariate analyses, such that cannabis did not uniquely predict cognitive outcomes. However, beyond other factors, heavier and early cannabis use was related to deficits in domains, such as decision-making, processing speed, visuospatial attention, and general cognitive abilities. A pattern of sex-specific effects emerged such that males performed more poorly than females on decision-making and processing speed tasks with cannabis use. Converging on Study 1 conclusions to explore the etiology of the most robust relationships, Study 2 found evidence that deficits in neurocognitive performance indexed pre-existing familial or environmental liability but may also in turn be adversely impacted by heavy and early cannabis use, specifically for IQ and, in males, decision-making performance. Collectively, this work suggests a complex relationship between nonacute cannabis use and cognition, with differences in cognition reflecting a mixture of premorbid familial risk factors and possible adverse consequences of cannabis exposure. This information has implications for shaping policy decisions and targeting prevention and intervention efforts to reduce negative consequences of cannabis exposure in youth.enAdolescenceCannabisCognitionTwinsYoung adulthoodThesis or Dissertation