For some years now, researchers have been observing a disturbing trend. Girls in the United States begin puberty much earlier than in previous generations. In fact, menstrual cycles start earlier in Latinas and Black girls.

Researchers have not yet determined a definitive cause. However, they believe this phenomenon is associated with adverse health outcomes later in life.

Loading the player...

“In pediatric practice, there’s been kind of a trend toward just assuming that Black girls go through puberty earlier. But what’s going on, and how? What are the health outcomes associated with that?” Dr. Juliana Deardorff, head of the Maternal, Child, and Adolescent Health program at the University of California, Berkeley, told the New York Times. “We should be thinking about this, not just normalizing these disparities.”

What did the researchers find?

Typically, the stages of puberty in girls begin around age 8. Although this sounds very young, the first physical changes of puberty begin around this age. The first sign is breast development. From then on, hair growth starts in different parts of the body. Acne also begins to increase, and finally, menstruation arrives.

For obstetricians, pediatricians, and gynecologists, the onset of menstruation is a sign of general health. However, researchers became concerned when they realized that the first signs of puberty began earlier and, therefore, so did menstruation.

According to the American College of Obstetricians and Gynecologists, girls usually are 12 to 13 years old when they first menstruate. However, a new study found that nearly 16% of women born between 2000 and 2005 were between 9 and 11 years old at the time of their first menstruation.

The new study is based on data from over 71,000 women who agreed to share health information through an iPhone app. It also found that more women experienced irregular cycles for three years or more after their first menstruation.

The case for Latinas and Black girls is more worrisome

According to the same study, some Latina and Black girls now perceive the first changes of puberty at ages 6 and 5, respectively.

“This is important because early menarche and irregular periods may point to physical and psychological problems later in life. And these trends may contribute to increased adverse outcomes and disparities,” said Zifan Wang, lead author of the study and a postdoctoral fellow.

According to another study from the UC Berkeley School of Public Health, precocious puberty in Latina and Black girls may be related to social inequality. The Berkeley team and researchers from Kaiser Permanente Northern California obtained data from more than 46,000 girls who received care at the medical institution from birth to middle adolescence.

“Our study suggests that neighborhood racial and economic privilege, as measured by ICE, may contribute to girls’ pubertal timing and racial/ethnic disparities therein,” the authors wrote. “Compared to girls born into neighborhoods of concentrated privilege, girls born into neighborhoods of concentrated disadvantage were significantly more likely to experience pubarche and thelarche at earlier ages,” independent of their individual racial/ethnic identity or socioeconomic status.

Long-term effects of early onset of puberty are of concern

According to several studies, precocious puberty and the early onset of menstruation are linked to cardiovascular problems and cancer. Similarly, entering puberty early has been linked to depression and anxiety.

“One of the things that’s striking about this study is that, historically, everybody has attributed these changes in menstrual cycles to increases in body fat and B.M.I.,” Dr. Deardorff said. But this study underlines that “even among people of healthy weight and potentially underweight, these trends are still occurring.” This means other factors might be at play.

For girls of color, however, the early onset of puberty brings with it another risk: hypersexualization. A 2017 study confirmed the association between exposure to childhood sexual abuse and earlier pubertal onset.

The study results also highlighted the possibility that, due to this early onset, survivors of sexual abuse are at increased risk for psychosocial difficulties and menstrual and fertility problems. Prolonged exposure to sex hormones may even cause reproductive cancers.