Some brain disorders are much more common in women than men, but why? A new study may help to shed light on this sex difference, after finding that many brain regions are much more active in women.

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Researchers find that women have higher brain activity in numerous regions.

Using a functional neuroimaging technique on more than 26,000 adults, researchers found that women have higher activity in numerous brain regions, including those associated with impulse control, anxiety, and mood.

Lead study author Dr. Daniel G. Amen, of Amen Clinics, Inc. in Newport Beach, CA, and colleagues recently published their findings in the Journal of Alzheimer's Disease.

When it comes to brain-related disorders, men and women are often disproportionately affected. Foe example, according to the Alzheimer's Association, around 5.5 million people in the United States are living with Alzheimer's disease. Of these individuals, around two thirds are women.

Studies have also found that women are almost twice as likely as men to develop depression over the course of a lifetime.

Many developmental disorders - such as autism and attention deficit hyperactivity disorder (ADHD) - however, are more common in males. According to the Centers for Disease Control and Prevention (CDC), autism is around 4.5 times more common in boys than girls.

But what are the reasons behind these sex disparities? According to Dr. Amen and team, it may be down to differences in brain activity.

Higher brain activity for women

The researchers came to their findings by analyzing brain scans from 119 healthy men and women, as well as 26,683 men and women who had been diagnosed with a psychiatric condition, such as ADHD, bipolar disorder, or schizophrenia.

Brain images for each participant were taken using single photon emission computed tomography (SPECT), a type of functional imaging technique that measures blood flow in specific brain regions, which is a good indicator of activity in that region.

SPECT imaging was conducted at study baseline and during a concentration task. In total, 128 brain regions were analyzed.

The study revealed that women showed much higher brain activity in more brain regions than men. For instance, at study baseline, their brain activity was increased in 65 brain regions, compared with only nine brain regions for men. During the concentration task, women showed increased activity in 48 brain regions, while men showed increased activity in just 22 brain regions.

Among women, brain activity was significantly higher in the prefrontal cortex (which is a region associated with impulse control and decision-making) and the limbic regions (which play a role in emotions, mood, and anxiety).

The team suggests that higher activity in these brain regions may explain why some mood-related disorders, such as depression, are more common among women, as well as why women generally have higher levels of empathy and self-control.

Men were found to have higher activity in brain regions that are related to visual processing and coordination, compared with women.

Overall, the researchers believe that their findings may help to explain the sex disparities in brain disorders.

"This is a very important study to help understand gender-based brain differences. The quantifiable differences we identified between men and women are important for understanding gender-based risk for brain disorders such as Alzheimer's disease."

Dr. Daniel G. Amen

"Using functional neuroimaging tools, such as SPECT, are essential to developing precision medicine brain treatments in the future," adds Dr. Amen.