For the past 50 years, researchers have known that girls who get their periods earlier than their peers are more psychologically vulnerable as teenagers. They have more frequent and severe mental health problems, from depression to anxiety, eating disorders, delinquency, substance abuse and failing or dropping out of school. But next to nothing was known about how long those problems last.
A new study suggests they could persist for years.
Tracking nearly 8,000 girls from adolescence through their late 20s – far longer than other studies have – a Cornell University researcher says girls who get their periods earlier than peers are likely to experience depression and antisocial behaviour well into adulthood. The study, “Age at Menarche, Depression and Antisocial Behavior in Adulthood,” was published Dec. 26, 2017, in Pediatrics.
The average age at which most girls get their periods is now around 12.5 years old.
“It can be very easy for people to dismiss the emotional challenges that come along with growing up as a girl, and say, ‘Oh, it’s just that age; it’s what everyone goes through,'” said Jane Mendle, author of the study and associate professor of human development. “But not everyone goes through it, and it’s not just ‘that age.’ And it’s not trivial. It puts these girls on a path from which it is hard to deviate.”
The researchers found the younger the girl began menstruating, the more likely she was to report symptoms of depression. By the time the study participants were nearly 30 years old, the links between early periods and depression were still clear. And the magnitude of the association was just as strong as it was in adolescence, years before, Mendle said, adding: “To me, that was the most interesting finding: that the effect lingered at the same strength.”
Earlier-maturing girls in the study also reported more frequent antisocial behaviours as teenagers, with more acting out, rule-breaking and delinquency. And that behaviour only got worse as they grew up. That’s the exact opposite pattern normally developing teens display, Mendle said. “Usually people aren’t shoplifting at 25 as much as they do at 15. … But these kids did not show the typical age-related declines in antisocial behaviour, and their behaviours got worse.”
Mendle and her co-authors, Rebecca Ryan of Georgetown University and Kirsten M.P. McKone of the University of Pittsburgh, analyzed data from the National Longitudinal Study of Adolescent Health. The nationally representative study tracked 7,800 women for 14 years (1994-2008), starting when they were between 11 and 21 years old. They were asked the age at which they began menstruating if they had symptoms of depression and antisocial behaviour and other factors associated with early puberty and mental health problems, such as household income and whether their father was absent.
The age at which most girls get their periods has become younger and younger over the past 50 years. But an even more dramatic, and worrisome, change has occurred in the younger ages at which girls enter puberty and start to develop breasts, Mendle said. About one-third of American girls are now entering puberty by the age of eight.
Girls who experience puberty earlier than their peers are at risk for mental health problems as teenagers because there’s such a mismatch between how they look and their emotional and cognitive maturity. “What’s tricky is because they look older, they start to get treated like they’re older. But they still have the internal mental workings of their normal chronological age,” Mendle said. Parents tend to grant them more autonomy. They tend to be the targets of sexual harassment and rumours at school. And it can be hard for these girls to maintain their friendships with others who are maturing at a different rate, she added. “It’s that cumulative effect.”
Why do these psychological problems last through adulthood? The researchers hypothesize it’s because the propensity for depression seems to have been sustained over time. “That’s the subject of our next study,” she said.
A lack of understanding about the long-term effects of early puberty is a public health issue, and paediatricians must be aware of how long these psychological problems can last, she said: “These are real people, with real lives. They’re not just data points. Early puberty is one extra risk factor that seems to be putting them on a different path.”
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