WP:

MONDAY, Dec. 17 (HealthDay News) — For girls, especially, having friends of the opposite sex during adolescence can raise the likelihood for alcohol use. Researchers at Virginia Commonwealth University analyzed data on 4,700 twins in Finland. They focused on the association between friendship characteristics and alcohol use and the extent to which genetic and/or environmental factors influenced similarity in drinking behaviors among adolescents and their friends. “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,” corresponding author Danielle Dick, now of Virginia Commonwealth University, said in a prepared statement. Dick was an assistant professor at Washington University in St. Louis at the time of the study.

Perhaps future studies will look into whether there is any correlation between premarital sex and girls having friends who are boys. Or if there is any connection between a girl leaving her room and an increased likelihood she’ll have outside influences on her life.