Browsing by Subject "marijuana"

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    Adolescent Behavioral Disinhibition And Its Relationship To Marijuana Use Development
    (2019-03) Zellers, Stephanie
    Behavioral disinhibition is a highly heritable risk factor for drug use, yet how it relates to marijuana use development is under-studied. We addressed this using independent twin samples from Colorado (N=2608) and Minnesota (N=3630), assessed from adolescence to early adulthood. We fit a biometric latent growth model of marijuana use using data from up to four waves of assessment between ages 14-24, to examine change in marijuana use and its relationship with a factor model of behavioral disinhibition. The factor structure of behavioral disinhibition, as well as its association with early marijuana use (r~.8) and increase in use (r~.3), was similar in both states. Early use was moderately heritable in both states. Increase in use was highly heritable in Minnesota (h2 =.81) but not Colorado (h2 =.14), and shared environmental effects were larger in Colorado (c2=.53) than Minnesota (c2=0). State differences in variance components could reflect state differences in culture or legal landscape. We found significant genetic correlations between disinhibition and early use in both states, as well as between disinhibition and increase in use in Minnesota (rg=.37). Lastly, exploratory analyses in Minnesota indicate that marijuana use decreases across the late 20s. This decline is strongly heritable (h2=.79) and moderately, negatively correlated with adolescent disinhibition (r=-.54). We conclude that adolescent behavioral disinhibition is positively related to early marijuana use and increase in use and negatively related to decrease in use in adulthood. This study broadens our understanding of adolescent risk and later marijuana use.
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    Effects of Youth Cannabis Use on Young Adult Functioning
    (2016-08) Hamdi, Nayla
    Youth cannabis use is associated with psychiatric problems, cognitive impairment, educational underachievement, and unemployment. Individuals with genetic liabilities, such as carriers of the catechol-O-methyltransferase (COMT) Val allele, may be particularly sensitive to the effects of cannabis use, but evidence for gene-by-environment (GxE) interaction is inconclusive. It is also unclear if youth cannabis use causes negative outcomes, or if unmeasured factors are responsible for both cannabis use and functional problems. Two studies were conducted to elucidate the nature of the association between youth cannabis use and young adult functioning. Both studies were based on a prospective sample of 1512 twins from the Minnesota Twin Family Study who were assessed six times from age 11 to age 29. The first study examined whether adolescent-onset cannabis use interacts with genetic factors to increase psychotic traits and impair attention and memory at age 29. The results revealed that adolescent-onset cannabis use is associated with higher levels of psychotic traits and worse memory regardless of genotype, with no evidence for GxE interaction. The second study examined if twins discordant on youth cannabis use disorder (CUD) have different psychiatric, cognitive, educational, and occupational outcomes at ages 20, 24, and 29. This design controlled for genetic and other familial confounds shared between twins. Analyses showed that many associations between youth CUD and psychosocial problems were attributable to familial confounding. Still, there was residual evidence for a potential causal effect of youth CUD on the development of other illicit drug use disorders and on deficits in numerical reasoning, even after controlling for premorbid functioning.