A 5-year study points to something disappointing that happens to girls who have sex before age 17

When it comes to having sex, girls who do it are often punished, whereas boys are congratulated for it.

And, according to a recent study, this double standard starts early in life: The study followed nearly 1,000 kids between the ages of 11 and 16, and found that girls who became sexually active lost friends, whereas boys of the same age who had sex actually gained them.

The opposite was true of making out: Girls who made out with their partners but did not have sex gained more friends, whereas boys who only made out lost friends.

"We see a really strong double standard when it comes to sex," study researcher Derek Kreager, a sociologist at Pennsylvania State University, told Business Insider.

In this double standard, women are punished by their social network for having sex too soon, whereas men are encouraged to have sex. And women are rewarded for more modest behavior like making out, while men who take it slow are looked down on, Kreager said.

Though the researchers found a correlation between having sex and the number of friends each gender had, the researchers preface that other factors, such as attractiveness or athleticism, could be at play and that having sex doesn't necessarily cause a loss or increase in friends.

Moreover, the study focused mainly on sexually precocious kids, so the findings do not apply to the general population - especially since studies show that the average person doesn't start having sex until around age 17.

The double standard starts early

A lot of previous research has documented how college students view men versus women who are having sex, but students at this age are generally more open to the idea of having sex and less quick to judge a person based on their sexual habits, Kreager said.

By contrast, this study looked at the transition from not having sex to having it, when people are just starting to form an opinion about sexual behavior and can, therefore, judge others more harshly for an act they don't fully understand.

Kreager and his colleagues used data from the PROSPER longitudinal study (PROmoting School-community-university Partnerships to Enhance Resilience), which tracked two groups of kids from 28 rural communities in Iowa and Pennsylvania from 2003 to 2007, from sixth to ninth grade (11 to 16-years-old).

The students completed a series of five surveys which asked about whether they were sexually active. The surveys also asked students to nominate up to seven best or close friends in their grade, as well as how many close friends they had outside of their grade or school.

Kreager and colleagues then compared the number of friends students had with the age at which the students started making out and/or having sex.

The pattern the researchers saw was pretty striking: Girls had 45% fewer friends after they reported having sex as before, whereas when boys had 88% more friends than before they started having sex.

But the opposite was true for students who reported making out only. When girls started making out but not having sex, they gained 25% more friends, whereas when boys made out but did not have sex, they lost 29% of their friends.

Of the students in the study, only about 15% of girls and 10% of boys were having sex by the ninth grade. Still, the apparent consequences that having sex has on friendships "are long-lasting, even for people who don't have sex early," Kreager said.

The findings, which have not yet been published in a scientific journal, will be presented this week at the Annual Meeting of the American Sociological Association (ASA).