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Illicit drug use and abuse/dependence: modeling of two-stage variables using the CCC approach. Addict Behav

Department of Human Genetics, Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Box# 980003 Suite 1-154, Richmond, VA 23298-0003, USA.
Addictive Behaviors (Impact Factor: 2.76). 07/2005; 30(5):1043-8. DOI: 10.1016/j.addbeh.2004.09.007
Source: PubMed

ABSTRACT

Drug use and abuse/dependence are stages of a complex drug habit. Most genetically informative models that are fit to twin data examine drug use and abuse/dependence independent of each other. This poses an interesting question: for a multistage process, how can we partition the factors influencing each stage specifically from the factors that are common to both stages? We used a causal-common-contingent (CCC) model to partition the common and specific influences on drug use and abuse/dependence. Data on use and abuse/dependence of cannabis, cocaine, sedatives, stimulants and any illicit drug was obtained from male and female twin pairs. CCC models were tested individually for each sex and in a sex-equal model. Our results suggest that there is evidence for additive genetic, shared environmental and unique environmental influences that are common to illicit drug use and abuse/dependence. Furthermore, we found substantial evidence for factors that were specific to abuse/dependence. Finally, sexes could be equated for all illicit drugs. The findings of this study emphasize the need for models that can partition the sources of individual differences into common and stage-specific influences.

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    • "In addition, although examining levels of use of the various substances as opposed to lifetime incidence is more informative in young adulthood, this approach assumes that the same factors influence no versus any use and any versus more frequent use. Multistage modelling showed that there is a substantial overlap in genetic and environmental factors influencing earlier and later stages of substance use, but also that there are factors that contribute specifically to later stages of use3435. Finally, although our dataset is relatively "
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    • "However, given that SUD is contingent on use, and that use of all illicit substances was influenced by a C c factor, it is puzzling that we did not find a C c factor for SUD. Agrawal et al. (2005) found use and SUD of any illicit drug to be correlated 0.67 in males (Agrawal et al. 2005). This implicates that the C c factor for illicit substance use would in average explain 18 % of the variance in SUD. "
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    • "For the latter, the influence of shared environmental factors is relatively stronger. Findings from twin studies assessing multiple stages of substance involvement suggest, at least partly, common genetic and environmental risk factors for substance use and misuse among adolescents and adults (Agrawal et al., 2005; Fowler et al., 2007; Kendler et al., 1999). "
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