INDICATORS OF GENETIC AND ENVIRONMENTAL INFLUENCE IN ALCOHOL-DEPENDENT INDIVIDUALS

Although much is known about genetic and environmental influences in a lcohol dependence at the population level, little is known about the r elative contribution of such influences on individuals. As an initial step toward individual assessment, concordance for the Diagnostic Inte rview Schedule, version III alcohol symptoms was determined in a sampl e (n = 113) of male monozygotic (MZ) and dizygotic (DZ) twins. Items w ere assigned to a genetic or environmental scale on the basis of signi ficant MZ/DZ differences in proband-wise concordance rates. Weights we re assigned to items based on factor analyses. For the genetic scale, significant differences were found between MZ and DZ intraclass correl ations. No significant differences were found between MZ and DZ correl ations on the environmental scale. When scores on the environmental sc ale were controlled, genetic scale scores were correlated with earlier age of onset of alcohol problems and a shorter interval between first intoxication and onset of alcohol problems. When scores on the geneti c scale were controlled, environmental scale scores were correlated wi th later age of onset of alcohol problems and a longer interval betwee n first intoxication and onset of alcohol problems. These results sugg est it is possible to assess relative influence of genetic and environ mental factors in individual cases of alcohol dependence.