Information on the heritability of the development of alcohol dependence
could provide a better understanding of the importance of genetic components
in disease transition.
To examine the genetic and nongenetic contributions to the age at onset
of regular alcohol use, the age at diagnosis of alcohol dependence, and the
transition from regular alcohol use to alcohol dependence.
Classic twin study.
This study included 3372 twin pairs of known zygosity from the Vietnam
Era Twin Registry. The diagnosis of DSM-III-R–defined
alcohol dependence and related information were obtained through telephone-administered
interviews conducted in 1992.
Main Outcome Measures
Standardized proportions due to genetic vs nongenetic factors of the
total variation in twin resemblance on the age at onset of regular alcohol
use, the age at meeting criteria for a diagnosis of alcohol dependence, and
the transition period from regular alcohol use to a diagnosis of alcohol dependence.
Genetic influence accounted for 49% of the variation in the age at diagnosis
of alcohol dependence. After adjusting for co-occurring psychiatric diseases,
additive genetic factors still explained more than 37% of the variance in
age at onset of alcohol dependence and at least 25% of the variance in the
transition period between regular drinking and the diagnosis of alcohol dependence.
Additionally, after grouping participants as early and late regular users
of alcohol, the genetic effects on the transition period for early regular
users were statistically significantly greater than those for late regular
Our results demonstrate a substantial heritable basis for alcohol dependence
according to its developmental sequence, including age at onset of regular
use, age at diagnosis, and the transition period between regular use and diagnosis.