COMPONENTS:

Component IV: Heritable Early Indicators of Risk for Drug Dependence

This study is currently reassessing the approximately 1400 pairs of general-population adolescent twins previously interviewed. The overall goal is to use an augmented twin study to understand how genes and environmental influences contribute to vulnerability to drug abuse and antisocial behavior.

Principal Investigator: John K. Hewitt
Co-Investigators: Robin P. Corley, Soo Rhee, Susan Young

Component IV initially assessed 2857 twins and 625 of their siblings between the ages of 12 and 19 years. We are currently completing the five year follow-up interview for these individuals.

• Together with nuclear family and adoptive families in Components II and III, this component is providing extensive normative epidemiological and family data.
• Combined analyses (with Components II and III) of the community sample of twins, adoptees, control adolescents, and their families data have established the heritability of drug use, abuse, and symptoms of dependence for specific substances and for general vulnerability; and contributed to the definition of a clinically valid, familial, and heritable Dependence Vulnerability phenotype for QTL analyses.
• We have established the heritability of conduct disorder in adolescence.
• We have quantified the extensive correlation between conduct problems and substance problems in adolescence and determined that a heritable behavioral inhibition phenotype may underlie this comorbidity.
• Motivated a series of new hypotheses, tests of which will substantially advance our understanding of the relationship between genes, antisocial behavior, and the development of adolescent substance dependence.

Link to the Longitudinal Twin Study (LTS) website - twins and their siblings involved in the LTS compose a portion of the Component IV sample.