A twin study of early cannabis use and subsequent use and abuse/dependence of other illicit drugs

Virginia Commonwealth University, Virginia Institute for Psychiatric and Behavioral Genetics, Department of Human Genetics, Richmond, VA 23298-0003, USA.
Psychological Medicine (Impact Factor: 5.94). 11/2004; 34(7):1227-37. DOI: 10.1017/S0033291704002545
Source: PubMed

ABSTRACT Cannabis use is strongly associated with the use and abuse/dependence of other illicit drugs. Gateway and common liabilities models have been employed to explain this relationship. We sought to examine this association using a combination of the discordant twin design and modeling methods.
We assess the relationship between early cannabis use and the subsequent use and abuse/ dependence of other illicit drugs in a population-based sample of male and female twin pairs using four analyses: (i) analysis of the association between early cannabis use and other illicit drug use and abuse/dependence in the entire sample of twins, (ii) assessment of the influence of early cannabis use in twin 1 on twin 2's use or abuse/dependence of other illicit drugs, (iii) use of twin pairs discordant for early cannabis use in a discordant twin design and (iv) a model-fitting procedure.
We found: (i) a strong association between early cannabis use and use and abuse/dependence of other illicit drugs in the sample, (ii) twin 1's early cannabis use is significantly associated with the twin 2's other illicit drug use, (iii) the role of correlated genetic factors with some evidence for a causal influence, and (iv) the correlated liabilities model fits the data well.
Early cannabis use is strongly associated with other illicit drug use and abuse/dependence. The relationship arises largely due to correlated genetic and environmental influences with persisting evidence for some causal influences.

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Available from: Michael C Neale, Sep 28, 2015
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    • "As members of an MZ twin pair share 100% of their genetic makeup and their shared environment, any observed differences between these discordant twins (i.e., an MZ OR significantly >1) are due to individual-specific environmental factors. As detailed elsewhere (Agrawal et al., 2004; Grant et al., 2012), the association between bulimic behaviors and early risky behaviors could result from (i) correlated familial factors that contribute to both phenotypes (expected discordant MZ OR = 1); (ii) a third unmeasured individual-specific factor that contributes to both phenotypes but is not shared by members of the twin pair (expected discordant MZ OR > 1); or (iii) a combination of the 2 (expected discordant MZ OR > 1 but less than discordant DZ and general population OR). Conditional logistic regression analyses examined whether the twin who reported the early risky behavior had higher odds of engaging in bulimic behaviors than her cotwin who did not engage in the early risky behavior, after accounting for genetic and shared environmental effects. "
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    ABSTRACT: Background Bulimic behaviors (i.e., binge eating and compensatory behaviors) and substance use frequently co-occur. However, the etiology underlying this association is poorly understood. This study evaluated the association between bulimic behaviors and early substance use, controlling for genetic and shared environmental factors.Methods Participants were 3,540 young adult women from the Missouri Adolescent Female Twin Study. A telephone adaptation of the Semi-Structured Assessment for the Genetics of Alcoholism interview assessed DSM-IV bulimic behaviors, substance use, and other psychological characteristics. Lifetime bulimic behaviors were examined in twin pairs concordant and discordant for early substance use. Logistic regressions were adjusted for the nonindependence of twin data, zygosity, age, body mass index, early menarche (onset before age 12), and early sex (first consensual sexual intercourse before age 15).ResultsIn the entire study population, women who reported early use of alcohol or nicotine were more likely to engage in bulimic behaviors after adjusting for covariates. In 53 pairs of monozygotic twins discordant for alcohol experimentation before age 15, the twin who reported early alcohol experimentation had 3.21 (95% confidence interval = 1.54 to 6.67) times higher odds of reporting bulimic behaviors than the cotwin who did not report early alcohol experimentation, even after adjustment for covariates.Conclusions Findings suggest that early alcohol experimentation may contribute to the development of bulimic behaviors via mechanisms extending beyond shared vulnerability, including individual-specific environmental experiences or causal pathways.
    Alcoholism Clinical and Experimental Research 08/2015; 39(9). DOI:10.1111/acer.12829 · 3.21 Impact Factor
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    • "Several sociodemographic and psychiatric variables and indicators of substance use severity predicted progression, including being male, urban residence , being never married, separated or divorced, having a broad range of psychiatric disorders or a family history of SUD, and early onset of cannabis use. Our results, in line with previous findings (Agrawal et al., 2004; Fergusson et al., 2006; Fergusson & Horwood, 2000; Lynskey et al., 2003; Van Gundy & Rebellon, 2010) suggest that a large proportion, but not all, of individuals who use cannabis go on to use other illegal drugs. Moreover, in agreement with the predictions of the GH, a minority of the total NESARC sample reported used other illicit drug before cannabis or only used other illicit drug. "
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    ABSTRACT: Background While several studies have shown a high association between cannabis use and use of other illicit drugs, the predictors of progression from cannabis to other illicit drugs remain largely unknown. This study aims to estimate the cumulative probability of progression to illicit drug use among individuals with lifetime history of cannabis use, and to identify predictors of progression from cannabis use to other illicit drugs use. Methods Analyses were conducted on the sub-sample of participants in Wave 1of the National Epidemiological Survey on Alcohol and Related Conditions (NESARC) who started cannabis use before using any other drug (n = 6,624). Estimated projections of the cumulative probability of progression from cannabis use to use of any other illegal drug use in the general population were obtained by the standard actuarial method. Univariate and multivariable survival analyses with time-varying covariates were implemented to identify predictors of progression to any drug use. Results Lifetime cumulative probability estimates indicated that 44.7% of individuals with lifetime cannabis use progressed to other illicit drug use at some time in their lives. Several sociodemographic characteristics, internalizing and externalizing psychiatric disorders and indicators of substance use severity predicted progression from cannabis use to other illicit drugs use. Conclusion A large proportion of individuals who use cannabis go on to use other illegal drugs. The increased risk of progression from cannabis use to other illicit drugs use among individuals with mental disorders underscores the importance of considering the benefits and adverse effects of changes in cannabis regulations and of developing prevention and treatment strategies directed at curtailing cannabis use in these populations.
    International Journal of Drug Policy 08/2014; 26(2). DOI:10.1016/j.drugpo.2014.07.011 · 2.40 Impact Factor
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    • "The original answer categories (ranging from never to 40 times or more) were recoded into 'never' and 'at least once.' Cannabis use is rare among adolescents aged 12–16; if adolescents at this age already have experience with cannabis use, this is generally interpreted as an (extreme) risk behavior. Early cannabis use has been found to affect neurocognitive functioning (Schweinsburg et al. 2008) and has been associated with an increased risk for problems later in life, including substance abuse and dependence (Lynskey et al. 2003; Agrawal et al. 2004), depression (Patton et al. 2002), and psychosocial adjustment problems (Fergusson et al. 2002). "
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    ABSTRACT: Previous research has provided considerable support for idea that increased parental support and control are strong determinants of lower prevalence levels of adolescent risk behavior. Much less is known on the association between specific parenting practices, such as concrete rules with respect to smoking and drinking and adolescent risk behavior. The present paper examined whether such concrete parental rules (1) have an effect on the targeted behaviors and (2) predict other, frequently co-occurring, risk behaviors (i.e., cannabis use and early sexual intercourse). These hypotheses were tested in a nationally representative sample of 12- to 16-year-old adolescents in the Netherlands. We found that both types of rules were associated with a lower prevalence of the targeted behaviors (i.e., smoking and drinking). In addition, independent of adolescent smoking and drinking behaviors, parental rules on smoking predicted a lower prevalence of cannabis use and early sexual intercourse, and parental rules on alcohol use also predicted a lower prevalence of early sexual intercourse. This study showed that concrete parental rule setting is more strongly related to lower levels of risk behaviors in adolescents compared to the more general parenting practices (i.e., support and control). Additionally, the effects of such rules do not only apply to the targeted behavior but extend to related behaviors as well. These findings are relevant to the public health domain and suggest that a single intervention program that addresses a limited number of concrete parenting practices, in combination with traditional support and control practices, may be effective in reducing risk behaviors in adolescence.
    Prevention Science 09/2012; 13(6). DOI:10.1007/s11121-012-0286-1 · 2.63 Impact Factor
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