In the family where I grew up, where most of the biological fathers are absent and household stress is common, it is not that unusual for the girls to start their periods early, in some cases as young as age 9, and to have bodies shaped like 16-year-olds when they are barely 12. Puberty is an awkward stage for most people, but for children who hit puberty earlier than what is considered normal for their peers, it can be more challenging—and even risky.
Along with the obvious problems of earlier sexual maturity, such as a younger interest in and from (sometimes older) boys, research has linked early puberty for girls to early sexual activity, eating disorders, and depression during adolescence, and even a higher risk of sexual abuse. But the negative effects of early puberty extend beyond adolescence, where it may lead to poorer health outcomes in adulthood, including mental health problems, heart disease, and cancer.
The early onset of puberty for girls and even boys is increasing in many countries around the world and for reasons that researchers are still trying to pinpoint. One study involving 11-year-old girls in the U.K. found that those from the poorest income families were twice as likely to experience early menstruation (by age 11) as those from the highest income families. A U.S. study found that living with a stepfather (for girls) and low socio-economic family status “predicted” early puberty. Childhood obesity is another risk factor. Other studies have identified racial differences in the onset of puberty.
A new study from Australia is the first in that country to investigate the cumulative effects of poverty from birth on early puberty in both boys and girls. The study, which was published in May in Pediatrics, included nearly 3,700 boys and girls from The Longitudinal Study of Australian Children, who were followed from birth through early adolescence. The team of researchers—Ying Sun, Fiona Mensah, Peter Azzopardi, George Patton, and Melissa Wake—wanted to know how household socioeconomic position, or SEP (measured by family income, parental education, and parental employment), affects early puberty in boys and girls, so they compared the SEP of children who started puberty early to those who started puberty later.
They assessed early puberty in the children at ages 8 and 9 and again at ages 10 and 11 based on the parents’ reports of early signs, such as the development of pubic hair and breasts in girls (those who had already started menstruation were in the early puberty group), and facial hair and voice changes in boys. In the study, 19.2% of boys and 21.1% of girls were classified as being in early puberty.
Family socioeconomic disadvantage significantly increased the risk of early puberty, especially in boys. The study found that boys in the lowest income households were four times more likely to exhibit signs of early puberty. Girls from the most economically disadvantaged families were nearly twice as likely to experience early puberty. More specifically, about 40% of boys and 28% of girls in the most economically distressed households entered puberty early, versus 12% of boys and 16% of girls in the highest income families.
The researchers controlled for a variety of factors known to be associated with early puberty that might influence their results, such as birth weight, the presence of a stepfather (for girls), parental early onset of puberty, and childhood obesity. Even after controlling for these and other factors, the authors note that “[a]lthough current adiposity was strongly correlated with early pubertal onset, the effects of household social disadvantage remained significant.” Moreover, in boys, “cumulative exposure to extremely unfavorable household SEP…independently predicted a fourfold increase in the rate of early puberty.”
Writing about the findings, lead author Ying Sun, an associate professor and visiting scholar from China to the Murdoch Children’s Research Institute, acknowledged that “we still don’t know exactly how poverty or disadvantage triggers early puberty.” However, she also observed:
Research on the biology of stress shows how major adversity, like extreme poverty, can permanently set the body’s stress response to high alert, affecting the brain’s circuits. This might, in turn, influence how reproductive hormones are regulated, so affecting the timing and trajectory of puberty … Another theory is that in the face of hardship—for instance, economic disadvantage, harsh physical environment, the absence of a father—children may be programmed to start the reproductive process earlier to ensure their genes are passed on to the next generation.
Whatever the causes, the long-term health risks associated with the early onset of puberty for both girls and boys make it a critical area for future research.
Editor's Note: The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or views of the Institute for Family Studies.