Kids getting older younger — KGOY, as it’s known — is not just a cultural phenomenon. Girls are literally hitting puberty at a younger age, and alarming the health community, since early onset puberty is often associated with a higher incidence of breast cancer and of behavioral problems. Now a new study has suggested that fathers may have a hand in how their daughters mature.Researchers from University of California, Berkeley, have discovered that girls who live in homes without a biological father physically mature sooner than those who live with their biological father. People had always assumed this was because girls in such homes were more likely to have poorer diets and, thus, higher body mass index (BMI), a ratio of height to weight that determines obesity.
But here’s the head-scratcher: early puberty is more prevalent among white non-Hispanic girls who live in relatively well-off homes, ones where the household income is higher than $50,000. And the absent dad effect held even when weight was taken into account.
“The age at which girls are reaching puberty has been trending downward in recent decades, but much of the attention has focused on increased body weight as the primary culprit,” said the study’s lead author Julianna Deardorff, U.C. Berkeley assistant professor of maternal and child health. “The results from our study suggest that familial and contextual factors — independent of body mass index — have an important effect on girls’ pubertal timing.”
The findings, published in the Journal of Adolescent Health on Sept. 17, were drawn from a longitudinal study by Kaiser Permanente on the environmental factors affecting puberty, which has so far followed 444 girls since they were 6 to 8 years old. (These results are from the first two years of analysis.)
The paper suggests a number of possible explanations for the absent father effect. It may be that other unrelated men in the home, be they stepfathers or boyfriends, give off pheromones that set off the girls’ biological clocks. However, the presence of other unrelated men in the home didn’t seem to alter the results.
Then again, a recent Australian study found that having older brothers can delay the onset of puberty in girls. The more older brothers a woman has, the older she is when she gets her first period. So it may be that male relatives have some kind of dampening effect on the whole girl-to-woman thing.
Another line of thought suggests that homes where the biological mother and father are not raising the family together can be less stable, and maturing early is a reaction to the instability. Artificial light from computer screens and TVs is known to increase the speed of puberty, and these would likely be more prevalent in higher income single parent homes. And there’s also a correlation between early puberty and some haircare treatments that contain placental products.
Perhaps the most controversial hypothesis is that it has something to do with mothers, not fathers. A study published this week, which my colleague Bonnie Rochman wrote about here, showed that weak maternal bonding can jump-start puberty. It may be that mothers who have jobs that pay them more than $50,000 are not home as much. “It’s possible that lack of emotional closeness may be bringing it on,” says Deardorff.
Working mothers, please remember, I am just the messenger.