Sex-specific changes in cerebral blood flow may begin at puberty, according to a recent study.

Researchers from the University of Pennsylvania School of Medicine found that cerebral blood flow levels decreased similarly in males and females before puberty, but saw them diverge sharply in puberty, with levels increasing in females while decreasing further in males, which could give hints as to developing differences in behavior in men and women and sex-specific pre-dispositions to certain psychiatric disorders. 

Puberty is the defining process of adolescent development, beginning a cascade of changes throughout the body, including the brain.

"These findings help us understand normal neurodevelopment and could be a step towards creating normal 'growth charts' for brain development in kids. These results also show what every parent knows: boys and girls grow differently. This applies to the brain as well," Theodore D. Satterthwaite, researcher and assistant professor in the Department of Psychiatry in the Perelman School of Medicine at the University of Pennsylvania, said in a statement. "Hopefully, one day such growth charts might allow us to identify abnormal brain development much earlier before it leads to major mental illness."

For the study, researchers imaged the brains of 922 youth ages 8 through 22 using arterial spin labeled (ASL) MRI. The participants were all members of the Philadelphia Neurodevelopmental Cohort, a National Institute of Mental Health-funded collaboration between the University of Pennsylvania Brain Behavior Laboratory and the Center for Applied Genomics at the Children's Hospital of Philadelphia.

The research team observed age-related difference in the amount and location of blood flow in males versus females. They also saw flow declining at a similar rate before puberty and diverging markedly in mid-puberty.

At around age 16, while the cerebral blood flow values of male continue to decline with advanced age, females cerebral blood flow values actually increased.

Researchers said this resulted in females having notably higher cerebral blood flow values than males by the end of adolescence.

The difference between males and females was most notable in parts of the brain that are critical for social behaviors and emotion regulation such as the orbitofrontal cortex.

"We know that adult women have higher blood flow than men, but it was not clear when that difference began, so we hypothesized that the gap between women and men would begin in adolescence and coincide with puberty," Satterthwaite said.

The researchers believe that such differences could be related to females' well-established superior performance on social cognition tasks. Potentially, these effects could also be related to the higher risk in women for depression and anxiety disorders, and higher risk of flat affect and schizophrenia in men.

Previous studies on have shown that puberty is an important source of sex differences. Previous work has shown that cerebral blood flow values declines throughout childhood, but the effects of puberty on properties of brain physiology such as CBF, also known as cerebral perfusion, are not well known.

The findings were recently published in the journal Proceedings of the National Academy of Science.