Girls who go through puberty and develop physically earlier than their peers are at risk of low self-esteem as well as emotional and behavioral problems. Research has also indicated that they are at a heightened risk of experiencing physical or sexual violence.

Probing more deeply into this increased risk of abuse, a new study led by the University of Pennsylvania's Sara R. Jaffee has found that early-maturing girls are more likely to be the victim of abuse from a dating partner if their friend group contains more boys.

"We knew that these girls are more likely to be victimized generally and became interested in whether there were particular characteristics of girls' friendship groups that might exacerbate that risk," Jaffee said. "We didn't expect the number of boys in a group to have a big impact, but that emerged as a primary moderator of this risk of being abused in a dating relationship."

The findings were published in the journal Pediatrics. Jaffee collaborated on the study with former Penn graduate student Frances R. Chen, now of Georgia State University, and Emily F. Rothman of Boston University.

The research relied on publicly available data collected from 3,870 girls, ages 13 to 17, from the National Longitudinal Study of Adolescent to Adult Health. All had reported being in one or more dating relationships. The survey asked girls to report their age at their first menstrual period, an objective measure of pubertal development, and whether they were more or less physically developed than their peers, a subjective measure. The girls were also asked whether their dating partner had engaged in any of a number of forms of abuse, such as swearing at them, insulting them in public, pushing or shoving them or threatening violence.

The dataset had information about the survey participants' friendships, as the surveys were administered to many students in the same schools.

"What's unique about this longitudinal study is that they ask every kid in the school, Tell me five of your closest friends," said Jaffee. "So you can figure out things like what proportion of kids in a friendship group are older or younger, boys or girls."

When Jaffee and colleagues analyzed the data, their results confirmed that girls who developed earlier were at a greater risk of dating abuse. They found that a girl who is a standard deviation more advanced than her same-age, same-race peers in pubertal development has a 14 percent increased risk of dating abuse.

And while the researchers had originally expected that perhaps having a lot of older friends might make a difference, or perhaps a relatively large number of older male friends, their findings suggested that simply having more male friends was the biggest aspect of the girls' friendship groups that contributed to an increased risk of dating abuse.

Jaffee said that she suspects girls who mature early receive more attention from boys. If they also have more male friends, then that increases the number of people expressing interest.

"If they're having more boys asking them out on dates or expressing interest, then the odds of one of those boys being abusive are higher," she said.

This risk may be exacerbated by the greater likelihood of early-maturing girls having problems with self-esteem and mental health.

"I think these girls sometimes have fewer tools to cope with relationships that are becoming abusive or have already become abusive," Jaffee said.

The findings, she said, point to a need for parents and pediatricians to have conversations with children about healthy relationships, "particularly if your daughter is maturing more quickly than their peers.

"These are conversations that parents find really uncomfortable, but this underscores that they need to be happening, for parents of girls and boys," said Jaffee. "And pediatricians may want to be on the look-out for early development in girls as a marker of risk. It's not determinative, not every girl is going to have problems, but it's a factor to consider."

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