*The following is excerpted from an online article posted on HealthDay.
A girl who gets her first menstrual period early in life -- possibly as young as 7 -- has a greater risk for developing depression and antisocial behaviors that last at least into her 20s, a new study suggests.
"Girls who go through puberty earlier than peers tend to be more psychologically vulnerable during adolescence," said study lead author Jane Mendle, a clinical psychologist and associate professor of human development at Cornell University.
It hadn't been clear, though, whether that vulnerability extends past the teen years. That's where the current study comes in. Mendle and her colleagues followed a group of almost 8,000 young women into their late 20s.
"Girls who went through earlier puberty are still showing higher rates of depressive symptoms and antisocial behavior than their peers well over a decade past adolescence," Mendle said.
An early first period is a sign of early puberty.
Mendle said there's no consensus on what constitutes an early first period, but girls in the study got their first period at age 12, on average. Some girls had their first period as early as 7 years old, though that was rare: Less than 1 percent of the girls had a first period that young.
However, nearly 7 percent of the girls had their first period at age 10, and 19 percent at age 11, according to the study, published online Dec. 26 in Pediatrics.
The cause of early puberty is generally not known, said Dr. Ellen Selkie, an adolescent medicine specialist with the University of Michigan and author of an editorial accompanying the study. There's also no proven way to prevent early puberty, she said.
Mendle said that other research has suggested that obesity or exposure to endocrine-disrupting chemicals may play a role. Such chemicals are found in plastics and flame retardants, she said.
Whatever the cause of early puberty, the new study found that it appears to have lasting consequences.
"Puberty has repercussions for virtually all domains of life," Mendle said. "Even though it's a biological transition, it's accompanied by dramatic changes in social roles and relationships, emotions and how kids think about themselves and others and their place in the world."
That said, she added that early puberty likely plays only a small role in contributing to depression and antisocial behaviors. And the current study was not designed to prove a direct cause-and-effect relationship.
"Even if a girl goes through earlier puberty, it doesn't mean she will necessarily struggle as an adult in the ways shown in our study," Mendle said. "It's an added risk, and one worth paying attention to. But depression and antisocial behavior are complicated and determined by many different factors, aside from when puberty happens."