Gender Differences in Responses to Stress: It Boils Down to a Single Gene
Fight-or-Flight vs Tend-and-Befriend
Posted March 17, 2012
You are walking alone in a dark alley late at night when, all of a sudden, you feel the barrel of a gun pressed to the back of your neck and hear a voice saying: "Give me your wallet or I will kill you." What do you do? The answer is: it depends on whether you are a man or a woman. If you are a man, you either run away as quick as you can or you turn around and punch the guy in the face. If you are a woman, you try to talk yourself out of the situation: "Are you sure you want to do this?" you ask the robber, or "If you put the gun away, we can talk about the situation and I will see what I can do to help you."
According to some psychologists, there is basic difference in the way men and women respond to social stress: for men, it's either "fight or flight" while for women it's "tend and befriend." Physiologist Walter Cannon - a pioneer of research on stress - argued in the 1930s that "fight-or-flight" is a universal physiological response to stress shown not only by all humans, but by animals as well. This response is controlled by the sympathetic nervous system - the part of our nervous system that deals with automatic functions such as breathing. Under stress, this system is activated, increasing heart rate and blood pressure, hastening breathing, and otherwise readying you to face down your enemy or to run. Thousands of studies inspired by Cannon described and documented this response in a variety of species and situations. The vast majority of these studies, however, were conducted with males.
In 2000, UCLA social psychologist Shelley Taylor and her colleagues wrote an influential article in Psychological Review, which Taylor later expanded into a book called The Tending Instinct, to propose that when it comes to stress, women are different from men. Instead of getting ready to fight or to flee, women become more likely to express affiliative social behavior, either to befriend the enemy - if there is an enemy and is causing the stress - or to seek social support from their family members or friends. Physiologically, instead of releasing large amounts of norepinephrine and cortisol into the bloodstream the way men do, Taylor argued that women respond to stress by secreting more endorphins - neurochemical substances that help alleviate pain and make us feel good about social interactions - and oxytocin, a neurohormone that is linked to the motivation to behave in a friendly manner to children or close social partners.
In support of Taylor's hypothesis, I can tell you from experience that if you put two adult male rhesus monkeys who have never met before in a small cage, they will fight and try to kill each other. In contrast, if you put two females in a cage, they will reduce the tension and awkwardness of the situation by exchanging grooming behavior (grooming is the main form of affiliation in monkeys and is known to cause a release of endorphins and to reduce stress in the receiver - not unlike receiving a body massage from your favorite masseuse).
A new study conducted in Australia suggests that the difference between men and women in their responses to stress may boil down to a single gene. The authors of this study argued that the SRY gene that men have on their Y chromosome - right between the gene for flipping through TV channels with the remote control and the gene for not putting the toilet seat down after peeing - causes their fight-or-flight response, while women use different genetic and physiological mechanisms to deal with stress.
The SRY gene was previously thought to be involved only in the development of male genitalia in the womb, but the proteins produced by this gene have now been found also in the brain and other organs. It turns out that these SRY proteins regulate the secretion of neurotransmitters known as catecholamines, which include norepinephrine, dopamine, and serotonin, and play an important role in neural activity, cardiovascular function, and movement. The SRY gene and its proteins may contribute to the release of large amounts of norepinephrine in the blood stream and the increase in blood pressure and motor activity occurring after stress in men, which in turn, facilitate the expression of the fight-or-flight response. Since women don't have the SRY gene, their responses to stress are regulated by other genes and other physiological changes involving estrogen hormones and, as previously mentioned, oxytocin and endorphins. These physiological changes, in turn, facilitate the expression of the tend-and-befriend response.
Obviously, women too show increases in catecholamines and in blood pressure after stress. These physiological processes are controlled by multiple genes, with the result that male and female physiology are generally more similar than Australian researchers might think. This is true also for other physiological gender differences, where men differ on average from women but there is overlap in the distribution of the trait. For example, although men have, on average, much more testosterone in their body than women, there are women whose testosterone is as high as, or even higher than men's testosterone. Recent studies conducted in Australia have shown that when these high-testosterone women respond to stress, particularly stress caused by men such as being held at gunpoint by a guy in a dark alley, they show the unique and highly effective "kick-the-man-in-the-groin" response.
Taylor, S. E., et al. (2000). Biobehavioral responses to stress in females: tend-and-befriend, not fight-or-flight. Psychological Review, 107: 411-429.
Taylor, S. E. (2002). The Tending Instinct: How Nurturing is Essential to Who We Are and How We Live. New York: Henry Holt.
Lee, J., Harley, V. (2012). The male fight-flight response: A result of SRY regulation of catecholamines? BioEssays, published online on March 8th.
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