en years ago, shocking new guidelines for pediatricians advised that girls who start to develop breasts and pubic hair at age six or seven are not necessarily "abnormal." In fact, by age eight, 48 percent of African American girls and 15 percent of white girls are showing clear signs of puberty.

 The guidelines were published in Pediatrics, the journal of the American Academy of Pediatrics, and were based on several studies.¹ The most important is Marcia Herman-Giddens’ study of 17,000 girls between the ages of three and 12 who were patients in more than 200 pediatricians’ offices across the country.² Although published in 1999, the study was based on girls evaluated in 1992-93. Previous standards of "normal puberty" were set more than 30 years ago, based on a study of fewer than 200 girls in a British orphanage in the 1960s.

When pediatricians revised their guidelines on puberty in 1999, they emphasized that the likely cause of younger girls starting puberty was the obesity epidemic. It is well-established that obesity affects hormones, and hormones affect obesity.

In May 2009, a Danish study was published in the same journal, which reported that Danish girls today are developing breasts at an earlier age than they were 15-years ago, which was the time of the earlier U.S. study.³ The Danish study found that the onset of puberty (as measured by breast development) dropped from a mean age of 10.9 in 1991 to 9.9 in 2006. This was not due to obesity, because the girls’ Body Mass Index (BMI) remained constant.

Redefining "normal"

If early puberty is not abnormal, does that mean there is nothing to worry about? What are the implications for young girls in early elementary school who are developing breasts and pubic hair at a time when they are still playing with dolls and Junior Monopoly?

The pediatricians in both studies reported that breast development was starting much earlier than menstruation, and that the age of menstruation was not changing substantially. In the 1990’s, when the U.S. study was conducted, the average age of an American girls’ first menstruation is similar to what it was a generation ago: 12.1 years old for African Americans and 12.8 for white girls. The average age for beginning menarche dropped 3.5 months from 1991 to 2006 for the Danish girls.

Since girls’ growth is slowed after puberty, pediatricians had been concerned about the girls’ height, and these concerns were alleviated when they learned that girls with early breast and pubic hair development grew to normal heights. As a result of these normal developmental milestones, the pediatricians seemed content to redefine normal development.

Parents and other health care professionals have a different perspective. There are reasons for their concerns: Research suggests that early puberty may have negative implications for girls’ mental health and their quality of life.

The trouble with normal

There are few well-designed studies of the psychological or social impact of early puberty, and most evaluate the experiences of girls who menstruate at an early age, rather than the larger number of girls who are developing breasts and pubic hair at an early age. Although common sense would suggest that a nine- or ten-year-old girl who looks like a teenager might feel self-conscious or have trouble making friends with classmates, researchers are only beginning to study these girls. Much remains unknown; however, the data suggest potentially serious problems:

• Girls who started menarche (menstruation) earlier tend to begin dating and having sexual intercourse younger than their classmates, according to a national study of 1,800 girls between the ages of 15 and 19. Among white and Hispanic girls (but not African American girls), early menarche was associated with earlier marriage.⁴
• Girls who matured early experienced more psychological stress, and were more vulnerable to deviant peer pressures and fathers’ hostile feelings, in a study of 200 adolescents.⁵
• A study of 33 girls from six to 11 years of age who experienced precocious puberty (secondary sexual characteristics before age nine) found that they have more behavior problems than other girls. They were more likely to be depressed, aggressive, socially withdrawn, have sleeping problems, and report obsessive behavior.⁶
• In a study of 1,700 high school students from Oregon, those who report that they matured earlier than their classmates were more likely to drink and smoke, and twice as likely to have had substance abuse and disruptive behavior disorders. They also tend to have lower self-esteem, poorer coping skills, miss more days of school, and were more likely to attempt suicide.⁷

Unanswered questions

If starting menstruation at an early age is associated with so many problems for girls and adolescents, does that mean that early development of breasts and pubic hair will have a similar effect? We don’t know. For example, if such problems as being socially withdrawn are caused by feeling different from the other girls, this may not be a problem for a girl surrounded by classmates who are also experiencing early signs of puberty. It could, however, be a terrible problem for an early developing African American girl in a third grade class with later-developing white girls. If, on the other hand, problems like depression and aggression are caused by hormonal changes associated with early development, it will not matter as much to an early developing nine-year-old girl how many other classmates look just like her.

Teenage pregnancy, sexually transmitted diseases, and the emotional trauma of sexual abuse are also serious concerns. Maturing young girls will have to cope with their own confusing sexual feelings as well as the impact that their appearance has on boys and men. Whether a 10-year-old girl becomes sexually active because hormonal changes influence her sexual interest, or because her appearance attracts older boys and men, the result could be the same. Young girls will need help to prevent them from being sexually abused or exploited, and from the risks of "consensual" sexual activity.

Of course, a major question is: what is causing early puberty? Ten years ago, most American endocrinologists were pointing to obesity as a major cause, since obesity affects hormones and vice versa. However, the recent Danish study shows that even if obesity contributes to early puberty, it is certainly not the only cause. During the last decade, a growing body of literature on the hormonal effects of common chemicals in the environment, such as phthalates and Bisphenol A (BPA), has resulted in increased concern that early puberty could be influenced by prenatal exposures as well as exposures during childhood.

In summary, more research is needed to learn about the causes and consequences of early puberty, and to initiate strategies to prevent early puberty and help those who are already affected. The implications for girls’ mental health and the quality of their lives—as children and adults-- cannot be ignored.

NOTES

1   Kaplowitz, PB, Oberfield, SE, The Drug and Therapeutics and Executive Committees of the Lawson Wilkins Pediatric Endocrine Society, Reexamination of the age limit for defining when puberty is precocious in girls in the United States: Implications for evaluation and treatment, Pediatrics, 1999; 104: 936-941.

2   Herman-Giddens, ME, Slora, EJ, Wasserman, RC, et al., Secondary sexual characteristics and menses in young girls seen in office practice: A study from the pediatric research in office settings network, Pediatrics, 1997; 99: 505-512.

3   Aksglaede, L, Sorenson, K, Petersen, JH, et al., Recent Decline in Age at Breast Development: The Copenhagen Puberty Study, Pediatrics, 2009; 123: 932-939.

4   Phinney, VG, Jensen, LC, Olsen, JA, and Cundick, B, The relationship between early development and psychosexual behaviors in adolescent females, Adolescence, 1990; 25: 321-332.

5   Ge, X, Conger, RD., Elder, Jr., GH, Coming of age too early: Pubertal influences on girls' vulnerability to psychological distress, Child Development, 1996; 67: 3386-3400.

6   Sonis, WA, Comite, F, Blue, J, et al., Behavior problems and social competence in girls with true precocious puberty, Journal of Pediatrics, 1985; 106: 156-160.

7   Graber, J, Lewinsohn, PM, Seeley, JR, Brooks-Gunn, J, Is psychopathology associated with the timing of pubertal development? Journal of the American Academy of Child & Adolescent Psychiatry, 1997; 36: 1768-1776.

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