When Lola was eight years old, she went through a massive growth spurt and started developing acne. Her mother, Elise, thought Lola was just growing fast because of genes inherited from her father. But when she noticed that Lola had grown pubic hair too, she was floored.
Collection: Coming of age: the emerging science of adolescence
A visit to an endocrinologist in 2023 confirmed that Lola’s brain was already producing hormones that had kick-started puberty. Lola had also been struggling emotionally. “She would have panic attacks every day at school,” says Elise, who lives in Minneapolis, Minnesota, and asked that her surname and Lola’s real name be omitted.
Although eight might seem young to start puberty, it’s not as rare as it once was. Data show that girls around the world are entering puberty younger than before. In the 1840s, the average age of first menstruation, or menarche, was about 16 or 17; today, it’s around 12. The average age for onset of breast development fell from 11 years in the 1960s to around 9 or 10 years in the United States by the 1990s. Some research hints that the trend mysteriously accelerated during the COVID-19 pandemic. (Although some data suggest that puberty is happening earlier for boys too, the shift seems to be less pronounced.)
Scientists have found a range of possible drivers for this change, with increasing body weight and obesity almost certainly playing a part. Some researchers suspect that exposure to hormone-disrupting chemicals or stress during childhood could be pushing puberty earlier, but studies have produced conflicting results. The trend has prompted the international organization the Endocrine Society to develop clinical-practice guidelines on puberty, to be published in mid-2026. The guidelines will reconsider how to treat girls on the border between typical and ‘precocious’ puberty, which has commonly been defined as before the age of eight in girls, but that some specialists argue should be younger.
Research over the past few years is also making the health risks of early puberty increasingly clear. Studies have linked it to greater risk of conditions including obesity, heart disease, breast cancer, depression and anxiety. Other research suggests that children who go through puberty earlier are more likely to experience discrimination because of their race or ethnicity, or otherwise be treated differently from their peers.
Families, researchers and clinicians are now trying to work out how best to adapt and when to intervene. This might involve medications to pause the process, but also better support and puberty education for children to protect them from some of the psychological and social risks. “We want to intervene right in that moment before people start internalizing some of those feelings of being othered,” says Michael Curtis, a family social scientist at the University of Minnesota in Minneapolis.
New normal
Technically, puberty begins when the brain’s hypothalamus begins producing pulses of gondatropin-releasing hormone. What triggers this process isn’t fully understood — it’s probably a complex interaction between genes and environmental factors. But the result is a hormonal cascade that leads to the release of the sex hormones oestrogen (in girls) and testosterone (in boys), which drive physical changes, including menarche. (The binary terms ‘girls’ and ‘boys’ are used in this article to reflect language used in studies and by interviewees.)
The drop in average age of menarche from the mid-nineteenth to the mid-twentieth century is often attributed to improvements in health, such as reductions in infectious disease and malnutrition (see ‘Younger puberty’). This probably sped up growth and sexual maturation. Most researchers assumed that the timing of puberty had remained relatively stable since then. “Studies from the 1960s showed that it was kind of levelling off at 12 and a half years,” says Paul Kaplowitz, a retired paediatric endocrinologist who was at Children’s National Hospital in Arlington, Virginia.
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