Illicit drug use and abuse/dependence: Modeling of two-stage variables using the CCC approach

A. Agrawal, M. C. Neale, K. C. Jacobson, C. A. Prescott, K. S. Kendler

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


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.

Original languageEnglish
Pages (from-to)1043-1048
Number of pages6
JournalAddictive Behaviors
Issue number5
StatePublished - Jun 2005


  • Abuse
  • Dependence
  • Illicit drugs
  • Twin
  • Use


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