Genetic and environmental influences on adolescent substance use and abuse

The inheritance of substance use and abuse among adolescents was investigat ed in a sample of 626 male and female 17-year-old twin pairs. Both licit (t obacco) and illicit (e.g., marijuana, amphetamines) substance use and abuse was assessed and analyzed using standard biometric methods. The heritabili ty of use and abuse of illicit substances was modest (25% or less), whereas the heritability of tobacco use and nicotine dependence was substantial (4 0% to 60%). There was no evidence that gender moderated the strength of gen etic influences. Shared environmental influences were substantial for all s ubstance use measures, The finding of greater genetic influence on the use and abuse of a licit substance than on the use and abuse of illicit substan ces suggests that inherited risk to drug abuse is considerably moderated by environmental control, at least in adolescence. The finding of significant environmental influences on all substance use measures underscores the imp ortance of intervention on early adolescent substance use, a known predicto r of adult substance abuse and dependence. Am. J. Med. Genet. (Neuropsychia tr. Genet.) 96: 671-677, 2000, (C) 2000 Wiley-Liss, Inc.