Consider these two cases:

One of my 12-year-old patients began to need a bra at age 8. Boys and girls teased her because she had adult-sized breasts. She got her first menstrual period when she was 9. She refused to go to school when she had her period because she was embarrassed to use the restroom. Her school grades declined, and she became clinically depressed.

A 13-year-old patient had her first period at age 10.  She began having sex at age 12 with much older males. When she came to my office for birth control, she had a positive pregnancy test as well as a positive test for a sexually transmitted disease.

Early development — is it normal? The development of breast buds is usually the first sign of puberty in girls and starts, on average, at age 10.  Some girls start as early as 8 and others not until 13, and this is considered normal. Girls should be checked by their pediatrician if they begin puberty before 8. Although they may be normal and healthy, there may be medical issues underlying this "too early" development. Menstrual periods usually occur about 18 months to two years after the onset of puberty — on average at age 12.5.

Normal but not mature.  Although an 8-year-old girl who has started to develop breasts and a 10-year-old girl who has experienced periods are likely healthy and developing normally according to their own biologic clock, their brains are still immature. Physical maturity may precede cognitive and emotional maturity, especially in girls, by years. Cognitive and emotional development is on a different schedule. Studies have shown that the capacity for control and coordination of thought and behavior, development of social awareness, and ability to understand the viewpoint of another person are still emerging during adolescence — and will continue to develop until a person's mid-20s or later.

"Not a girl … not yet a woman" The Britney Spears song is true. Bodies and brains are often out of sync. The burden of looking like a middle or late adolescent, while still being a child, can be enormous. A girl may be treated like a teenager because she looks mature, but in reality, she is just 8 years old. She may be teased and bullied, affecting school attendance and performance, and she may engage in risky behaviors. As a result of her youth, she is less able to manage and cope with social and emotional challenges, and with social media.

Early puberty may have lasting negative effects. The hormones that contribute to the physical changes of puberty affect emotional and psychological health in both boys and girls. While boys tend to have increased confidence and self-esteem when they develop on the earlier side of normal, this is not the case with girls. In fact, Contemporary Pediatrics recently reported on the results of a study that tracked the psychosocial effects of early puberty on girls longer than had been previously studied, beyond adolescence and into adulthood. When compared with girls who did not mature early, girls who went through puberty earlier showed higher rates of depressive symptoms and antisocial behavior at a young age that continued into their late 20s, according to the lead researcher.

My advice: If your daughter experiences early puberty, it is important to be aware of the risks and to be sensitive to her emotional and social vulnerability. Given what we know from the research, simply explaining to a child that her physical development is normal is not enough. Although all children benefit from a good doctor-patient relationship, it is especially important for a girl who has early development, and she may need additional help from a therapist or school counselor. Activities to help her excel at academics and sports will help to boost her confidence.

Above all, aware parents can help to prevent long-lasting mental-health problems if they understand the issues of early puberty and give a young daughter the extra time and attention she may need.