Researchers at the University of Pennsylvania and The Children's Hospital of Philadelphia have found that the amount of blood flow to the brain changes in adolescence -- but in different ways for girls and boys.
University of Pennsylvania psychiatrist and lead author of the study, Ted Satterthwaite, said scientists have known that adult women have higher blood flow than their male peers, but it was never clear when that happened.
"Were people born that way or not?" asked Satterthwaite. "And if they were similar early on, when did they diverge?"
To find out, the team measured the amount of blood flowing to the brain in more than 900 kids, teens, and young adults using an MRI-based technique.
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Publishing their results this week in the journal PNAS, Satterthwaite said boys and girls initially have similar blood flow levels, which decline in late childhood.
"But around age 16, whereas the boys, their blood flow continued to decline," he said, "the girls, it leveled out and actually increased from there."
By the end of their teens, Satterthwaite said women had 15 to 20 percent more blood flow to the brain than men.
It will require more testing, but Satterthwaite speculates that abnormalities in blood flow might be linked to mental illnesses. Psychiatric disorders often strike in young adulthood and with different frequency depending on the patient's sex. For example, young men are more prone to schizophrenia whereas young women are more likely to be anxious or depressive.
"These differences in blood flow potentially could, on one hand, make females more adept at social tasks," said Satterthwaite, "but potentially also lead to higher vulnerability to certain forms of symptoms of depression and anxiety."
Regardless, he said, the study's baseline information will be useful in creating growth charts for developing brains.
"We really should not lump boys and girls together," Satterthwaite said. "Just like they have different growth charts for height, and weight and head circumference, they probably need different growth charts for brain development also."