By Dennis Normile
WASHINGTON — Puberty has always been a time of stress and emotional turmoil for adolescents and for their parents. And scientists have long recognized that kids who start puberty ahead of their peers are particularly likely to have trouble getting along with other children and with adults. New research suggests that those difficulties can be traced back to even earlier ages, indicating that early puberty may not be the root cause.
Australian researchers drew on data for 3,491 children, roughly half boys and half girls, who were recruited at ages 4 or 5 and then followed until they reached ages 10 or 11. Every 2 years, a researcher visited each subject's home, evaluated the child, and interviewed the primary caregiver, which in most cases was a parent, who later completed and returned a questionnaire about their child's behavior. The primary caregiver was also asked to judge the child's pubertal status, based on indicators for an early phase of puberty such as breast growth in girls, adult-type body odor, and body hair; and growth spurts, deepening voices in boys, and menstruation in girls for a later stage.
Girls typically enter puberty at age 10 or 11 and boys at 11 or 12. The researchers found that 16% of the girls and 6% of the boys in the study had entered puberty early, at age 8 or 9. Previously, researchers thought that any negative effects of early puberty showed up only after puberty's onset. But by tracking a cohort of children from age 4 to 5 to age 10 to 11, they found that problems thought restricted to postpuberty children actually appeared well before puberty. Retrospectively, they were able to show that children who later had early onset puberty had difficulty playing with other children and participating in normal school activities, even when they were 4 or 5 years old. Boys, though not girls, in this group had also showed behavior problems, such as being overactive, losing their tempers, and preferring to play alone from a young age.
"The association between early-onset puberty and poor mental health appears to result from processes under way well before the onset of puberty," the researchers conclude in a paper appearing online Tuesday in the Journal of Adolescent Health.
Unusually early puberty "is opening up a broader window of vulnerability" for mental health problems among youths, says George Patton, the senior author of the paper who is a psychiatric epidemiologist at the Murdoch Childrens Research Institute in Melbourne, Australia. He explains that mental capacities for self-control of impulsive behavior do not normally accompany early puberty. This means that early puberty onset increases the risk of children harming themselves or falling into depression.
The paper challenges previous assumptions that puberty triggers behavior changes, says Jay Giedd, a psychiatrist at the National Institute of Mental Health in Bethesda, Maryland, who was not involved in the study. But he adds that the study raises new questions about what factors are influencing this behavior and whether early psychosocial and behavioral difficulties might somehow trigger early puberty.
The next stage of the research will try to provide some answers, says the study's lead author, Fiona Mensah, a social scientist also at the Murdoch Childrens Research Institute. "We will be looking to see whether we can identify the early life factors that may be influencing children's development and leading to early puberty," she says. They also want to understand how premature delivery, the home, and community environment might influence mental health.
The ultimate goal is to identify supportive measures to help children develop social and emotional resources before they reach puberty so that they can better navigate the storms of adolescence.