Genetic and environmental factors each play a different and defined role in alcohol dependence, a new study on 3,546 female twins has indicated.
Carolyn E. Sartor, postdoctoral research fellow at Washington University School of Medicine and corresponding author for the study, revealed that the participants ere 18 to 29-year olds from a longitudinal twin-based study of alcohol-related problems and associated psychopathology in female adolescents and young adults.
She said that retrospective reports of alcohol-use histories, collected through telephone interviews, were used to determine transition times between drinking milestones - from non-use to initiation, initiation to onset of first alcohol-related problem, and first problem to onset of AD.
She said that genetic factors appeared to contribute significantly to all three transition times, accounting for 30 to 47 per cent of the variance.
She further said that environmental factors unique to individuals also contributed significantly to the timing of all three transitions, but environmental factors shared by twins were influential only in the rate of progression from non-use to initiation of use.
"Our results indicated that heritable influences are traceable to a common factor, but the degree to which they shape the timing of transitions varies by stage in drinking course," said Sartor.
"Genetic factors appear to play a larger role in later-stage transitions than in the age at which girls begin drinking. By contrast, this first stage was the only one influenced significantly by aspects of the environment that are common to members of a twin pairs, such as shared peer influences," she added.
She, however, made it clear that the results of the study should not be interpreted to mean that alcohol-related problems are pre-determined.
"Drinking behaviours are influenced in large part by environment at all stages of alcohol use and are therefore modifiable. That being said, the substantial contribution of genetic factors to the rate at which problem drinking develops does mean that individuals with family histories of alcohol-use disorders are at increased risk and therefore especially important targets for prevention efforts," she said.
Telling about the significance of examining AD development in terms of transition points, Sartor said that the most potent genetic and environmental influences at each stage along the "pathway of risk" could be identified, and interventions tailored accordingly.
"For example, we found that environmental factors that make members of a twin pair more similar play a significant role in the age at which girls begin to drink. This suggests that the most effective strategies for delaying first alcohol use would be those that focus on such environmental factors as parental attitudes toward drinking, friends' alcohol use, and parental monitoring of adolescents' activities," she said.
Her team is now planning to extend their research to the examination of additional stages of drinking behaviours like cessation of alcohol use and genetic and environmental influences on the timing of transitions in the development of other substance-use problems.
She said that future studies would include both men and women so that possible gender differences could be detected.
A paper describing the current study has been published the journal Alcoholism: Clinical and Experimental Research.