Genes and the environment contribute differently to drinking among young adolescents

A 2001/2002 report by the World Health Organization found that, among young people in western countries who began drinking before 16 years of age, the average age of initiation was 12 years of age.

A new twins study from the Netherlands has found that genetic factors appear to be involved in the early initiation of alcohol use, while common environmental factors become involved once alcohol use has begun.

Results will be published in the June issue of Alcoholism: Clinical & Experimental Research and are currently available at OnlineEarly.

"A lot of studies examining alcohol use in adolescents have focused on several social factors in alcohol use, for example, the influence of friends and parents," said Evelien A. P. Poelen, a researcher at Radboud University Nijmegen, "while genetic factors have often been neglected. We thought both factors should be taken into account simultaneously in order to examine the relative contribution of both to the initiation and frequency of drinking."

Poelen and her colleagues used data collected through the Netherlands Twin Register to identify 694 twin pairs who were 12 to 15 years of age during survey years 1993, 1995, 1997 and 2000. Of these pairs, 125 were identical males, 89 were fraternal males, 183 were identical females, 106 were fraternal females, and 191 were fraternal of the opposite sex (in total, 619 males, 769 females). Initiation and frequency of drinking were analyzed as a function of three influences: genetic effects, common environmental effects, and unique environmental effects.

Results showed that genetic factors were most important for variation in early initiation of alcohol use, while common environmental factors explained most of the variation in frequency of drinking once alcohol use had been initiated.

"It is often assumed that initiation of use is mainly predicted by social factors, for example, family norms toward alcohol use," said Poelen. "This study shows that genetic factors are also involved in early initiation and that is a new perspective."

Given that genetics may be involved in alcohol use at such a young age, it is vitally important that these genes not be "triggered," she added. "Parents should delay the age of initiation of their adolescent children to alcohol, even within what may be considered a safe home environment."