Why does puberty always come earlier?

In recent decades, boys and girls have always developed earlier: according to some studies, the average age of onset of puberty in girls has dropped by three months every 10 years since the 1970s. Early puberty It does not just mean wearing sanitary pads and bras, or starting to shave and change your voice earlier than expected: early development would be associated with a greater risk during adolescence of suffering from depression, anxiety, drug abuse and other psychological problems. Not only that: having menarche earlier than normal could also increase the risk of developing breast and uterine cancers in adulthood. But what are the factors that contribute to an early onset of puberty? Experts don’t know for sure, but they put forward some hypotheses.

Obesity. One of the factors that affects the onset of puberty is body weight: several studies have shown that overweight or obese girls tend to develop earlier than normal weight ones. A British study from 2021 found that leptin, a hormone released by fat cells that restricts the feeling of hunger, acts on the part of the brain that also regulates sexual development. “There are not many doubts: obesity contributes to the early arrival of puberty nowadays,” Natalie Shaw, pediatric endocrinologist at the National Institute of Environmental Health Sciences, explains to the New York Times, stressing, however, that obesity cannot be the only explanation.

Chemical substances. A 2009 study of nearly 1000 girls in Copenhagen (Denmark) found that the average age of breast development was just under 10 (a year earlier than in a previous study in the 1990s), while that of the menarche around ai13 (about four months earlier than previous results): in this case, however, obesity could not be blamed because BMI (Body Mass Indexbody mass index) of the volunteers was the same as that of the girls involved in the previous research.

For this Anders Juul, author of the two studies, proposed an alternative theory: the blame for the early development was attributable to the chemicals with which the girls had come into contact during their life. In the 2009 study, he points out, the girls who developed breasts first were also the ones with the highest level of phthalates (substances used to make plastics more flexible) in their urine. Other analyzes, however, found no correlation between chemicals and early onset of puberty. This is why many scholars are skeptical of Juul’s theory.

Difficult experiences and pandemics. Other factors that could cause puberty to come early, at least in girls, would be related to stress and difficult life experiences: being sexually abused at an early age, having mothers suffering from mood disorders, living without a father biological – these are all experiences that could contribute to early development. Covid may also have played its part: according to an Italian study from 2022, more girls (but not boys) developed earlier than expected during the pandemic.

Outdated parameters? What emerges is a picture in which it is difficult to draw a clear pattern of cause and effect: several factors contribute to the early arrival of puberty, but none seem to be decisive. Perhaps the time has come to update our benchmarks, which are still those of the Tanner scale, based on observations conducted between 1949 and 1971 on 700 boys and girls who lived in an English orphanage. According to this scale, puberty should normally start at the age of 8 for girls and from age 9 for boys: if development begins earlier, it is necessary to check that the child does not suffer from a rare hormonal disorder called precocious puberty.

However, some doctors argue that, in light of the new studies, the minimum age considered normal for the onset of puberty should be lowered, otherwise healthy children may have to undergo unnecessary medical procedures. But not everyone agrees: many pediatricians argue that the risk of suffering from precocious puberty is still high, and therefore call for caution.