title: Illicit drug use and abuse/dependence: modeling of two-stage variables using the CCC approach.
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.
authors.affiliation: Department of Human Genetics, Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Box# 980003 Suite 1-154, Richmond, VA 23298-0003, USA. arpana_vipbg@yahoo.com
authors.forename: A
authors.initials: A
authors.lastname: Agrawal
authors.forename: M C
authors.initials: MC
authors.lastname: Neale
authors.forename: K C
authors.initials: KC
authors.lastname: Jacobson
authors.forename: C A
authors.initials: CA
authors.lastname: Prescott
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
mesh_terms: D000328:Adult; D019970:Cocaine-Related Disorders / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives; D013287:Illicit Drugs; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D008875:Middle Aged; D008954:Models, Biological; D015995:Prevalence; D012737:Sex Factors; D012931:Social Environment; D019966:Substance-Related Disorders / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics
chemical_list: D006993:Hypnotics and Sedatives; D013287:Illicit Drugs