The age at which girls enter puberty is quietly changing. What was once a phase that began in the early teenage years is now appearing much sooner for many children. Researchers say this trend is global and growing, with health experts closely examining the reasons behind it and the possible long-term effects.

How much earlier is puberty starting?

Studies show that this is not an isolated trend. A meta-analysis of 30 studies found that the global average age of puberty onset in girls fell by three months per decade between 1977 and 2013. Over that period, puberty began more than a year earlier overall.

The first visible sign of puberty in girls is usually breast development, followed later by menstruation, also known as menarche. Research published in May 2024 in JAMA Network Open suggests that both of these milestones are now occurring at younger ages.

The study examined data from 71,341 women born in the United States between 1950 and 2005. It found that girls are starting their periods earlier and are taking longer to develop regular menstrual cycles.

Over the 55-year study period, the number of girls experiencing early menarche, defined as starting periods before age 11, nearly doubled to 16 per cent.

What do experts say about this trend?

Lisa Swartz Topor, associate professor of paediatrics at The Warren Alpert Medical School of Brown University and Hasbro Children’s Hospital, says this pattern is well documented and seen globally.

She explains that the exact reasons remain uncertain. “There are more questions than answers,” she says.

Dr Topor adds that early puberty is likely caused by a complex combination of factors linked to major changes in the world over the past two centuries.

How does puberty actually begin in the body?

Puberty starts in the brain. A region called the hypothalamus releases a hormone known as gonadotropin-releasing hormone, or GnRH. This hormone signals the pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

In girls, LH and FSH prompt the ovaries to produce estrogen and progesterone. These hormones drive breast development, the growth of body hair, the start of menstruation and changes in body shape.

How can early puberty affect children emotionally?

Early puberty does not only bring physical changes. It can also affect how children feel and behave. Dr Natasha Chaku, a psychologist at Indiana University, explains, “Your child might start to look or act like a teenager before you expected.”

As a result, parents may need to talk to their children about body changes earlier than planned. Dr Chaku stresses, “Parents may need to have conversations about how their bodies are going to change earlier than they expect.”

Is childhood obesity playing a role?

One key factor experts point to is the rise in childhood obesity since the 1970s. Several studies have linked obesity to early or precocious puberty in girls.

Dr Aviva Sopher, associate professor of paediatrics at Columbia University Irving Medical Centre, explains that obesity can increase levels of hormones such as insulin, insulin-like growth factor 1 and leptin. These hormones influence appetite, fullness and fat storage, but they also interact with the reproductive hormone system.

Girls with obesity also tend to have higher levels of estradiol, a form of estrogen, which may trigger earlier breast development and puberty.

Does diet influence puberty timing?

Diet quality may also matter. Dr Frank Biro, professor of paediatrics at Cincinnati Children’s Hospital Medical Centre, explains that diets low in fruits and vegetables and high in animal protein and processed foods have been linked to increased estrogen levels.

A study in China compared three different diets and found that girls who ate more snacks, desserts, fried foods and sugary drinks were more likely to experience early puberty.

Can stress speed up puberty?

Stress is another important factor. A 2023 study published in Psychoneuroendocrinology found that high levels of stress in early childhood, including poverty or abuse, may raise the risk of early puberty in girls.

Dr Jane Mendle, a clinical psychologist at Cornell University, says, “The timing of puberty is stress-sensitive.”

Researchers believe this may be because both stress responses and puberty are regulated by the hypothalamic-pituitary-adrenal axis.

The COVID-19 pandemic may have added to the problem. Studies suggest that increased screen time, social isolation, unhealthy diets and reduced physical activity during lockdowns were linked to a recent rise in early puberty among girls in New York City.

What role do chemicals and pollution play?

Growing evidence points to the impact of environmental chemicals. Endocrine-disrupting chemicals such as phthalates and bisphenols, commonly found in plastics and household products, may interfere with hormone systems.

A 2023 study in BMC Medicine showed that exposure to perfluorinated compounds, found in items like stain repellents, paints, plastic cutlery and food packaging, may contribute to early puberty.

Air pollution may also be involved. Research published in Environmental Health Perspectives in 2023 found that girls exposed to higher levels of pollution during pregnancy and childhood may begin menstruation earlier.

What are the long-term health risks?

Dr Biro warns that early puberty is linked to higher risks of several health problems later in life. These include breast cancer, obesity, high blood pressure, type 2 diabetes, metabolic syndrome, abnormal cholesterol levels and heart disease.

Mental health can also be affected. Research shows that girls who enter puberty early may experience higher levels of depression, anxiety, stress and body image concerns, along with difficulties managing emotions.

When should parents seek medical advice?

If early puberty is suspected, Dr Biro advises parents to consult a healthcare provider. Doctors will usually monitor development and help families understand the physical and emotional changes involved.

In some cases, medication may be recommended to slow puberty. This can help reduce potential risks, including stunted growth, and support healthier development.