Browsing by Subject "Twins"

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    Cannabis use and cognition from adolescence to young adulthood: exploring cause, consequence, and influencing factors
    (2021-08) Bair, Jessica
    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.
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    Understanding Adjustment of Adolescents Conceived Using Medically Assisted Reproduction within Family Contexts
    (2019-05) Chen, Muzi
    Adolescents conceived using medically assisted reproduction (MAR), as a continually growing population in the U.S., may be at risk for adjustment problems due to three challenging parenting tasks faced by their families. These challenges include a high likelihood of parental pregnancy loss, raising twins, and whether and when parents should tell children about being conceived using MAR. This dissertation investigated psychosocial adjustment of MAR-conceived adolescents in relation to these parenting challenges within family contexts in two studies. Study 1 tested a moderated mediation model that proposes a possible family process through which a pile-up stressors of pregnancy loss and twin status indirectly influence adolescent psychosocial adjustment in a sample of 278 adolescents from 193 families. Results suggest pregnancy loss has long-lasting, differential effects on parental emotions at middle childhood when parenting twins versus singletons, which relates to subsequent adolescent adjustment. Study 2 examined adolescent psychosocial adjustment following the MAR information sharing within family communication environments using multiple group analysis in a sample of 163 adolescents from 115 families. Results indicate a complex picture that family communication environments interplay with the timing of MAR information sharing to influence adolescent psychosocial adjustment. These studies suggest a critical role of family contextual factors in shaping MAR-conceived adolescents’ psychosocial adjustment.