For the past 50 years, researchers have known that girls who get their periods earlier than their peers are more psychologically vulnerable as teenagers. They have more frequent and severe mental health problems, from depression to anxiety, eating disorders, delinquency, substance abuse and failing or dropping out of school. But next to nothing was known about how long those problems last.
The age at which most girls get their periods has become younger and younger over the past 50 years. But an even more dramatic, and worrisome, change has occurred in the younger ages at which girls enter puberty and start to develop breasts, Mendle said. About one-third of American girls are now entering puberty by the age of eight.
Scientists at Newcastle University in the U.K. have discovered that girls tend to optimize brain connections earlier than boys. The researchers conclude that this may explain why females generally mature faster in certain cognitive and emotional areas than males during childhood and adolescence. The new study was published on December 19, 2013, in Cerebral Cortex.
However, they found that not all projections (long-range connections) between brain regions are affected to the same extent for males and females: Changes were influenced differently depending on the types of connections. Changes in these connections have been found in many developmental brain disorders including autism, epilepsy, and schizophrenia. With many neurological diseases, there are widespread differences between the sexes. For example, autism spectrum disorders are almost 5 times more common among boys (1 in 54) than among girls (1 in 252).
Recent studies reveal that after birth girls are already better at reading faces and hearing human vocal tones. Incredibly, during the first two years of life a baby girl's ovaries will pump adult levels of estrogen. From six to nine months, a boy's testicles are flooded with adult levels of testosterone.
\"The studies that were done with children around 12 months old where their moms went in a room with them and they were told not to touch an object,\" recounts Dr. Brizendine. \"The boys would just go right for the object and touch it. The girls would hear their mom's voice, turn around, look at their mom's face, and stop. Boys don't hear the complete tones in the female voice.\"
\"The reason little girls may play better together is brain wiring -- verbal ability at a younger age,\" she continued. \"And they may just be able to negotiate the sharing better than boys. Of course, little boys and little girls act differently. Adult men and adult women act differently, too. But it has really been ignored until probably the middle '90s.\"
At puberty, there is again an explosion of hormones, according to Brizedine. As a female teen's brain emerges, hormones dramatically reorganize her brain circuitry, driving the way she thinks, feels, acts and even obsesses over her looks. Studies show that these surges of estrogen can trigger teen girls' need to become sexually desirable to boys.
To further illustrate how a teen's changing brain chemistry often molds their behavior, Dr. Brizendine invited ABC's 20/20 to listen as she spoke to students at the Marin School outside San Francisco. Girls, she explained, mature faster than boys, and girls' brains are as much as two years ahead during puberty.
Dr. Brizendine explains that the male amygdala, which also controls sexual thought, is twice as large as that of females. Fueled by testosterone, it triggers the typical teenage male brain to think about sex every 52 seconds, compared to a few times a day for teen girls.
When it comes to emotions, Dr. Brizedine says girls have their own area that's twice as large as boys' -- the hippocampus, which is the seat of emotional memory. The female brain uses many centers in both hemispheres that activate in response to faces, voices and expressions. Men, however, use only one side of their brain.
\"Actually, there is a hormone that gets released when girls are, sort of more intimate with each other -- in terms of talking and fixing each other's hair and doing stuff. That's called oxytocin. It's a hormone that's released in the brain that's kind of a \"feel good\" hormone.\"
The hormone oxytocin gives a surge of pleasure, the same rush a drug addict gets from taking cocaine or heroin.When it was time for the girls to ask a question, Heidi, one of the teens in the class asked, \"Why are guys able to like express everything sexually but not emotionally? Like, they can be like, 'Hey baby, what's up?' but, like, they can't, like, say, 'I'm sad.'\" 781b155fdc