Why Are Girls Starting Puberty Earlier?
Girls in the U.S. and around the world have been entering puberty at younger ages for decades, but scientists have not fully understood why. Now, new research from Columbia University Mailman School of Public Health suggests that stress, body mass index (BMI), and hormone patterns may work together to accelerate development in girls.
Columbia epidemiologist Lauren Houghton, PhD, the study's first author, explains the research behind the trend and offers recommendations for parents and caregivers.
What factors are contributing to earlier puberty?
Dr. Houghton and her Columbia team looked at hormone levels in girls before puberty began. They found that girls with higher levels of the stress hormones called glucocorticoids and reproductive hormones (specifically androgens and progesterone) were more likely to start puberty earlier.
"The findings challenge traditional assumptions that estrogen is the primary hormonal driver behind earlier puberty in girls," says Dr. Houghton.
Specifically, the study found that girls with higher levels of psychosocial stress and glucocorticoids, as well as higher body mass index (BMI), reached puberty an average of seven months earlier than girls with lower levels of these measures. Psychosocial stress can include challenges related to family, school, finances, or social relationships.
Higher BMI has long been associated with earlier puberty in girls. Researchers now believe BMI may interact with hormone production in more complex ways than previously understood. Body fat can convert androgens produced by the adrenal glands into estrogens, which may help trigger breast development. Higher stress levels may also influence this hormonal pathway.
The study is among the first to examine how stress, hormones, and BMI interact together rather than independently.
Why has puberty been starting earlier over time?
Earlier puberty has been observed globally over several decades. Age at first menstrual period is hovering around age 12, but breast development is continuing to shift earlier, including before age 8. Precocious puberty is a term used when these changes begin unusually early.
There is likely no single explanation, but potential contributing factors include trends in psychosocial stress, environmental exposures to various substances (such as endocrine-disrupting chemicals), nutrition, physical activity, and socioeconomic factors.
"The age at which a population begins puberty can be thought of as a metric of the overall health of a population," Dr. Houghton says. "Puberty age reflects whether individuals have enough resources, security, and energy to survive, grow, and reproduce. It also inherently reflects changes in hormones regulated by mind and body."
What can parents and caregivers do?
Puberty timing can vary widely among healthy children, and early development does not automatically indicate a medical problem.
Dr. Houghton encourages the following healthy lifestyle habits not only to help delay early puberty but also to improve long-term, overall health.
- Engage in regular physical activity
- Get enough sleep
- Reduce chronic stress
- Eat a healthy diet
- Get regular medical checkups
- Let the pediatrician know about any early signs of puberty appearing before age 8, such as breast development, body odor, and pubic or underarm hair
"The most important step is knowing one's body and tracking any changes. Destigmatizing puberty and menstruation by having open conversations can also help children feel more comfortable as they grow and change," says Dr. Houghton. "My neighbor's daughter recently left a note to her friends stating that she was so excited to share that she had breast buds. I welcome more body positivity like this around these normal changes for all children."
Lauren C. Houghton, PhD, is an assistant professor of epidemiology at the Columbia University Mailman School of Public Health.