Updated

Girls who hit puberty early are at sharply higher risk of abusing alcohol as teens if their parents don't keep tabs on them, new research shows.

Early-maturing girls whose parents gave them free rein at age 13 showed a "dramatic increase in alcohol abuse" over the next four years compared to early-maturing peers who were supervised more closely, Dr. Brett Laursen of Florida Atlantic University in Fort Lauderdale and colleagues found.

And over time, the more often these girls abused alcohol, the less closely their parents supervised them, according to research published in Pediatrics.

The researchers followed 957 girls from a small town in central Sweden over a four-year period, starting when the girls were 12 to 14 years old. Roughly 20% of the girls had their first period before age 12 ("early maturing"), about 60% first menstruated at age 12 or 13 ("on-time"), while the remaining 20% had their first period after age 13 ("late-maturing").

Alcohol abuse rose in all three groups as the girls got older. But among the on-time and late-maturing groups, levels of autonomy granted by parents (based on the girls' own perception) weren't associated with rates of alcohol abuse.

For the early-maturing group, however, parental autonomy granting made a big difference. Early-maturing girls whose parents gave them the least autonomy - that is, girls whose parents kept the tightest rein - had an 84% increase in alcohol abuse from seventh to tenth grade, while those given "medium" autonomy had a 160% increase in alcohol abuse. For those given the most autonomy, alcohol abuse increased by 234%.

The early-maturing group tended to hang out with older friends, who reported "relatively high" rates of alcohol abuse. But even after the researchers took this into account, the association between parental supervision and alcohol abuse remained.

Dr. Laursen and his colleagues also found that the girls who started out the study at higher levels of alcohol abuse were actually granted more freedom over time. From seventh to tenth grade, parental autonomy granting increased 12% for girls who started out at low levels of alcohol abuse, but it increased by 18% for those at medium levels of alcohol abuse and 24% for those with the highest levels of alcohol abuse.

"The more parents simply pay attention to what their child is doing, the less likely they are to do unhealthy things," said Dr. Terrill Bravender, a professor and division director of adolescent medicine at the University of Michigan Department of Pediatrics in Ann Arbor. Dr. Bravender wrote an editorial accompanying the new study. "The take-home message is be part of your children's life and know what they're doing, who they're with, and set up some appropriate boundaries for them, especially if they're early-maturing girls," he said.

It's not clear why parents in the study seemed to respond to their child's alcohol abuse by giving them even more freedom, he said. "You would hope that once kids started participating in these activities, that parents might find out."

They may assume that their early-maturing daughters are more grown-up than they really are, he added, or the increased autonomy granting may be due to parents' "learned helplessness."

The findings don't mean that being a helicopter parent is the way to go, according to Dr. Bravender. Instead, he added, "you should have a general idea of who your child's friends are, and who they're spending time with."

Dr. Laursen did not respond to an interview request by press time.