Teens who drink alcohol tend to have opposite-sex friends who do the same, and girls may be particularly vulnerable to the influence of their friends, Science Daily reported on Nov. 26.

Researchers from both the United States and Finland used data from a population-based, longitudinal twin study of behavioral development and health-risk factors from Finland comprising 4,700 individuals.

"Several studies have found that peer drinking has more of an influence on an adolescent's drinking than his or her own parent's drinking," said lead author, Danielle Dick, assistant professor at Washington University, St. Louis when the study was conducted. "Our findings suggest that girls may be more susceptible to their friends' drinking, and that having opposite-sex friends who drink is also associated with increased drinking for both sexes."

"Furthermore, genetically based analyses suggest that the correlation between adolescent/friend drinking was attributable to shared environmental effects across genders. This suggests that the association between an adolescent's alcohol use and that of his or her peers is not merely a reflection of genetic influences on the adolescent's own alcohol use that cause them to select drinking peers."

The risk factors associated with the peer network appeared to be stronger in girls, noted Kenneth J. Sher, Curators' Professor in the Department of Psychological Sciences at the University of Missouri.

"Those who design and implement prevention approaches should take gender into account as a potentially critical moderator of prevention outcomes," said Sher. "We need to better understand the 'why' of sex differences in risk in order to shed important light on the nature of risk processes. For example, are girls potentially more 'vulnerable' to peer-related effects at this stage of life because they are likely to be more intimately involved with their closest friends than are boys?" 

Both Dick and Sher cautioned parents to be aware of their child's friends and how they spend their time together.  

The study was published in the December issue of Alcoholism: Clinical & Experimental Research.