Doctors and epidemiologists have reported several factors that associated with earlier puberty. These include:
At the turn of the twentieth century, the age of girls at their first period was 16 years old in the UK. With improved nutrition this age had dropped to 13 years by the 1940s. Interestingly, the age of first menstruation is still 13, but breast development has got earlier and earlier since the end of the Second World War in the UK and USA.
In the past, the time from initial breast development to the first period was 18 months. This has now increased to 3 years, so puberty is lasting much longer than in the past.
The main factor that leads to earlier onset of puberty (usually marked by the beginning of breast development) is percentage body fat. In the USA today, one-fifth of girls are overweight, and breast development is commonly seen from 9 years old now.
There has been a rapid increase in obesity rates in all developed countries, in the UK 7 percent of children aged six to 11 were obese in 1980, nearly 18 percent were obese in 2012.
In the early 1990’s studies of American girls reported that breast development began on average at 8.87 years in African-Americans and 9.96 years in white girls with similar findings in Europe.
In 2013 the USA data reported that breast development had started by seven years in:
A 2015 study that tracked some 1,200 girls and their mothers’ breastfeeding habits found that breastfeeding and length of time a girl was breastfed correlated with later breast development in girls in some populations. This means that breastfeeding girls may offer a protective effect against early puberty.
Stress seems to bring on puberty earlier too with girls who experience chronic stress, e.g., girls raised in Romanian orphanages, going into puberty early.
There is also a so-called ‘Stepfather Effect’ and absent father effect on age of onset of puberty. Researchers have found that girls that live in a house with an adult man, e.g., a stepfather, that isn’t biologically related to them, are more likely to experience an earlier onset of puberty. Endocrinologists have speculated that there may be a pheromonal effect, either that unrelated adult males produce a chemical that promotes puberty or perhaps that related males (biological fathers) who live in the home with their daughters may produce a chemical that helps to suppress their puberty. These pheromonal effects have been found in other mammal species, e.g., meerkats and banded mongooses.
Girls who experience early puberty are at risk of a range of psychological and social difficulties. This stems from the fact that their physical development is years ahead of their emotional development.
When girls appear more physically developed, adults assume they also have a similarly advanced emotional development but the two are not linked. This leads to children being treated like adults.
Professor Jeanne Brooks-Gunn, a child development expert at Columbia University in the USA has reported the following risks in girls who experience early puberty compared to girls who enter puberty later than average:
Not all changes in adolescence are mediated by sex hormones, the adrenal glands also drive ‘adrenarche’.
Underarm hair and pubic hair is mediated by androgens from the adrenal glands that sit on top of the kidneys. This adrenal system or adrenarche also promotes the development of sweat production, increased skin sebum production and acne.
As puberty progresses in teenage girls, the ovaries themselves become the main site of androgens production (which is converted into testosterone).
However, if your daughter was born ‘small for dates’ because of intrauterine growth restriction, they may enter start developing body hair before breast development begins.
Some girls enter premature adrenarche and develop pubic hair, underarm hair, oily skin and increased perspiration in middle childhood. This can also be coupled with increased mood swings and may not be timed with breast development.
Nutrition and weight gain seem to be the biggest risk factor in early puberty. Looking at the data, it seems that exclusive and extended breastfeeding of a baby girl may delay the onset of puberty later in life. Throughout a girl’s life lots of physical activity and a balanced diet with help to prevent childhood obesity.
Extrapolating from link between extreme chronic and toxic stress in infancy (experienced by children in Romanian orphanages at the end of the Twentieth Century) and early puberty, it would seem that reducing or removing chronic stress will help to protect girls from early puberty as well as other risk factors such as future mental health problems and addictions. The most fundamental source of protection from chronic stress is a loving bond with a sensitive and available parent. For more information read our article about the affect of good attachment on emotional development in children.
There is treatment available for girls who experience very early puberty. This involves hormonal treatment to reverse puberty. This can protect bone maturity and reduce breast development. The former can help to maximise final height as girls who have early puberty may end up with a lower final height as the growth plates on the leg bones fuse after puberty which means they can miss out on a growth spurt if they have had an early puberty.
When children go into andrenarche or puberty early they can be offered hormone therapy too.
Julianna Deardorff PhD & Louise Greenspan MD (2014) ‘The New Puberty: How to Navigate Early Development in Today’s Girls.’ Rodalle Books
Graber, J. A., Nichols, T. R., & Brooks-Gunn, J. (2010). Putting pubertal timing in developmental context: Implications for prevention. Developmental Psychobiology, 52, 254–262.
Lynne, S. D., Graber, J. A., Nichols, T. R., Brooks-Gunn, J., & Botvin, G. J. (2007). Links between pubertal timing, peer influences, and externalizing behaviors among urban students followed through middle school. Journal of Adolescent Health, 40, 181e7-181e13.