His stress is not like her stress

Muscles tighten, the heart pounds and nausea takes hold: In the face of sudden stress, men and women respond alike. But when threats, scares or frustrations continue for days or months, differences between the sexes emerge.

Scientists have long known that women are more likely than men to suffer depression, post-traumatic stress disorder and other anxiety disorders, all of which have been linked to chronic stress, says Temple University psychologist Debra Bangasser. But until recently, studies of people’s responses to such stress have focused primarily on men.

Now, a growing number of scientists are studying what happens at the cellular and genetic levels in the brains of stressed-out rodents — male and female — to gain insight into the human brain. The studies are beginning to reveal differences between the sexes that may help explain the variability in their reactions and perhaps even provide much-needed insight into why stress-related disorders are more common in women than men.

Recent findings reported at the annual meeting of the Society for Neuroscience, held in Chicago in October, show that a common stress hormone triggers different responses in specific brain cells of male and female animals. The differences make females less able than males to adapt to chronic stress.

Other studies are exploring how exposure to the same hormone influences gene expression in a part of the brain that controls mood and behavior. Still other research suggests that a different hormone, associated with trust, could render females more susceptible than males to depression, anxiety and PTSD.

“Some differences may contribute to disease and some may not,” Bangasser says. “But given that it’s early days in this understudied area, we’re already finding interesting things.”

A heightened stress response may bring an evolutionary advantage. An enhanced response to stress hormones could help females — most often caregivers for the young — remain alert and ready to take action in a stressful environment.

The problems occur, Bangasser adds, “when the system is responding when it shouldn’t be or when it’s responding for a really long time in a way that becomes disruptive.”

While no one has managed to tie findings in animals to a specific behavior in people, the studies are an important first step in understanding how sex and hormones contribute to a person’s response to stress, she says. Insights from the studies also offer hope for finding ways to better detect and treat stress-related disorders in people of both sexes.