By John Dodge

CHICAGO (CBS) — Adolescent girls who have sex are more likely to lose friends, while the opposite occurs with boys, according to a new study that finds gender double standards begin at the earliest phases of sexual maturity.

In middle school or early in high school “girls friendship networks shrink significantly after they have sex,” said Derek Kreager, the lead author of the study and an associate professor of sociology and criminology at Pennsylvania State University.

Boys experience tremendous peer pressure to become sexually active.

According to Kreager, the boys experienced an 88 percent increase in peer acceptance if they had sex.

On the other hand, girls experienced a 45 percent decrease.

Girls were more likely to be accepted for “making out.”

Boys lost friends for doing the same thing.

“A sexual double standard then arises because women and girls who violate traditional sexual scripts and have casual and/or multiple sexual partnerships are socially stigmatized, whereas men and boys performing similar behaviors are rewarded for achieving masculine ideals,” the study noted.

Recent research, which shows men and women are held to different standards of sexual conduct, largely focused on college students and the so-called “hook up” culture.

By studying early adolescents, Kreager was able to show that sexual double standards also affect youth at a very young age.

“During early adolescence, peer evaluations of initial sexual behaviors and virginity loss are likely to have large and lasting impacts on later sexual adjustment,” Kreager said.

The study tracked 11- to 16-year-olds from rural Iowa and Pennsylvania between 2003 to 2007. A total of 921 students were surveyed in five waves: in the fall of sixth grade and in the spring of sixth, seventh, eighth, and ninth grades.

The study “The Double Standard at Sexual Debut: Gender, Sexual Behavior and Early Adolescent Peer Acceptance” was presented on Tuesday at the American Sociological Association conference in Chicago.