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
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 "
ABSTRACT: Aims: To determine 1) the prospective associations of conduct problems during early adolescence with tobacco, alcohol and cannabis use in young adulthood and 2) to what extent these associations are due to overlapping genetic versus environmental influences. Design: A prospective twin study using biometric twin modelling. Setting: Finland. Participants: 1847 Finnish twins (943 males and 904 females) were interviewed in early adolescence, of which 73% (N=1353, 640 males and 713 females) were retained in young adulthood. Measurements: Symptom counts of conduct disorder (CD) criteria were obtained from a semi-structured clinical interview in early adolescence (age 14-15 years, M=14.2, SD=0.15). Frequency of alcohol, tobacco, and cannabis use was obtained from a semi-structured clinical interview in young adulthood (age 19.9-26.6 years, M=22.4, SD=0.7). Findings: We found modest to moderate phenotypic correlations (r=0.16 to 0.35) between early adolescent CD symptoms and substance use in young adulthood. In males, the phenotypic correlations of CD symptoms with all three substance use variables are largely explained by overlapping genetic influences. In females, overlapping shared environmental influences predominantly explain the phenotypic correlation between CD symptoms and tobacco and cannabis use. Conclusions: Conduct disorder symptoms in early adolescence appear to moderately predict substance use in early adulthood. In males, genetic influences seem to be most important in explaining the relationship between conduct disorder symptoms and substance use whereas in females, shared environmental influences seem to be most important. This article is protected by copyright. All rights reserved.
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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. "
ABSTRACT: The specificity of genetic and environmental risk factors for illicit substance use and substance use disorders (SUD) was investigated by utilizing self and co-twin reports in 1,791 male twins. There was a high rate of comorbidity between both use of, and SUD from, different classes of illicit substances. For substance use, the model that included one common genetic, one shared environmental, and one individual-specific (i.e., unique) environmental factor, along with substance-specific effects that were attributed entirely to genetic factors fit the data best. For illicit SUD, one common genetic and one common unique environmental risk factor, and substance specific shared environmental and unique environmental risk factors were identified. Risk factors for illicit substance use and SUD are mainly non-specific to substance class. Co-twin rating of illicit substance use and SUD was a reliable source of information, and by taking account of random and systematic measurement error, environmental exposures unique to the individual were of lesser importance than found in earlier studies.
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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). "
ABSTRACT: The aims of the present study were to determine the direct effect of DRD2 and DRD4, as well as their interaction with parenting (i.e. rejection, overprotection and emotional warmth), on the development of regular alcohol and cannabis use in 1192 Dutch adolescents from the general population. Information was obtained by self-report questionnaires. Perceived rejection, overprotection and emotional warmth were assessed at age 10-12. Regular alcohol and cannabis use were determined at age 15-18 and defined as the consumption of alcohol on 10 or more occasions in the past four weeks, and the use of cannabis on 4 or more occasions in the past four weeks. Models were adjusted for age, sex, parental alcohol or cannabis use, and externalizing behavior. Carrying the A1 allele of the DRD2 TaqIA polymorphism, or the 7 repeat DRD4, was not directly related to regular alcohol or cannabis use. In addition, adolescent carriers of these genetic risk markers were not more susceptible to the influence of less optimal parenting. Main effects for parenting indicated that overprotection increased the risk of regular alcohol use, whereas the risk of cannabis use was enhanced by parental rejection and buffered by emotional warmth. Our findings do not support an association between DRD2/DRD4 and regular alcohol and cannabis use in adolescents. Given the substance-specific influences of rejection, overprotection and emotional warmth, these parenting factors might be promising candidates for prevention work.