"We found that different parts of the brain activate with different spatial and temporal profiles for men and women when they are faced with performance-related stress," says Dr. J.J. Wang, Assistant Professor or Radiology and Neurology, and lead author of the study published in Social Cognitive and Affective Neuroscience (SCAN).
The findings indicate that stress responses may be fundamentally different in each gender, sometimes characterized as "fight-or-flight" in men and "tend-and-befriend" in women.
The researchers believe that evolutionarily, males might have had to confront a stressor either by overcoming or fleeing it. On the other hand, females might have instead responded by nurturing offspring and affiliating with social groups that maximize the survival of the species in times of adversity.
According to the researchers, the "fight-or-flight" response is associated with the main stress hormone system that produces cortisol in the human body called the hypothalamic-pituitary-adrenal (HPA) axis.
During the study, 16 men and 16 women received fMRI (functional Magnetic Resonance Imaging) scans before, during and after they underwent a challenging arithmetic task—serial subtraction of 13 from a 4 digit number.
For increasing the level of stress, the researchers frequently prompted participants for a faster performance, and asked them to restart the task if they responded incorrectly.
As a low stress control condition, participants were asked to count backward without pressure.
Throughout the experiment, the researchers measured the subjects' heart rate and the levels of the stress hormone cortisol.
The researchers also measured the subjects' regional cerebral blood flow (CBF), which provides a marker of regional brain function.
In men, showed the study, stress was associated with increased CBF in the right prefrontal cortex and CBF reduction in the left orbitofrontal cortex.
In women, the limbic system, a part of the brain primarily involved in emotion, was activated when they were under stress.
While both men and women's brain activation lasted beyond the stress task, the lasting response in the female brain was stronger.
The neural response among the men was associated with higher levels of cortisol, while that among women did not have as much association between brain activation to stress and cortisol changes.
"Women have twice the rate of depression and anxiety disorders compared to men. Knowing that women respond to stress by increasing activity in brain regions involved with emotion, and that these changes last longer than in men, may help us begin to explain the gender differences in the incidence of mood disorders," said Dr. Wang.