A new study appearing in the journal Pediatrics now suggests that early puberty in girls can lead to depression and antisocial behavior well into adulthood, suggesting that the difficulties of those teenage years are far from fleeting.

Several animal studies, and basically all of human experience have taught us that puberty is a particularly difficult stage of life psychologically.

Researchers led by Dr. Jane Mendle at Cornell used data from the National Longitudinal Study of Adolescent Health, a nationally representative survey study which ran from 1994 to 2008. More than 10,000 girls, average age 16 years, were interviewed at the start of the study and followed into their late 20's. Over that span, they were asked about depressive and antisocial symptoms. They also reported the date of their first period, which is a proxy for pubertal development.

The average girl reported the onset of menarche at around 12 years, but there was a wide distribution, with about 10% of girls reporting a first period at age ten or younger.

The study showed that a younger age of menarche was associated with greater depressive symptoms in the later teen years.  Perhaps more interestingly, it showed that younger age at menarche was associated with more depressive symptoms even as the women approached 30 years of age.

In an elegant analysis, the authors went on to show that the driver of that elevated depression rate in later adulthood was the depression in the teenage years. In other words, girls who develop early are more likely to get depressed as teenagers, and that depression may set the tone for decades to come.

Now there are some factors here that were unaccounted for, body weight being a major one. Overweight and obese girls go through puberty earlier, and body weight is a risk factor for depression. I asked Dr. Mendle about this potential confounder.

"We know that people treat girls who look very physically mature different from girls who do not look physically mature and that is not purely attributable to weight. We know that parents do it and we know that teachers do it. There is also not any good evidence that weight would be influencing the antisocial and externalizing behaviors that were seen".

Clinically, whether early puberty is a sign of other stressors or a cause of distress in itself might not matter. If early puberty is associated with depression, the implication is that pediatricians should start screening for depression earlier in girls who develop earlier. The United States Preventative Services Task Force currently recommends screening for depression starting at age 12. For some girls, an even earlier intervention may have long-lasting effects.