We are not all the same when it comes to our reactions to stress, I rediscovered on Tuesday afternoon during a workshop sponsored by the International Brain Research Organization to mark Women’s History Month.
For example, the idea that our bodies’ involuntary stress reactions serve us well in the case of acute stress (short-term) but can cause harm when the stress is continued or chronic, may not be true for most of us, suggested Victoria Luine of Hunter College. She was one of the three main speakers during the session, called “Stress and the Brain: Effects on Addiction, Cognition and Well Being” and held at the Cosmos Club (which for its first 110 years was the most exclusive male-only club in Washington, DC).
“These relationships were determined scientifically in adult males,” she said. “The male response is fight or flight, but is the female’s?” She and others have been testing these other populations (in the rat world), and in some memory tasks, some cell-level investigations, and other work, they have found differences.
Stress improves spatial memory performance in females even as the same stress leads to a decrease in memory in males, she said. At the cellular level, stressed males lose dendrites, the offshoots of a neuron used to network with other neurons; stressed females do not. Other labs have replicated these results, and added their own similar findings. “It’s becoming evident that this isn’t an anomaly, Luine said. “Females get better, while males get worse.” Just as in males, Luine’s team sees a decrease in memory performance as we age, though motherhood may alleviate some of it (again, in rats).
Susan Weiss of the National Institute of Drug Abuse (NIDA) described how male-female differences pose a challenge in studying addiction, a chronic illness that recurs much the same way as high blood pressure or asthma. “Addiction is freqently co-morbid,” she said, accompanied by other illnesses, but the illnesses vary. For example, addiction accompanies anxiety and depression in many women,though in far fewer men; in men, overaggression is more common. Also,“for all the drugs we study, there are different motivations between men and women,” she said.
One similarity is environmental: One-half to two-thirds of people who have serious problems with addiction later in life had what researchers describe as “adverse childhood experiences.” Such experiences range from neglect, childhood abuse, and family trauma to living through war.
Following up on the childhood-experiences idea, Stephen Suomi of the Eunice Kennedy Shriver National Institute of Child Health and Human Development described some of the longitudinal research he and others are doing with a community of 400 or so rhesus monkeys at a large facility in western Maryland. Many monkeys raised in peer groups (without their mothers) have trouble later on joining the larger community and maintaining good social bonds. One mother-related behavior is gazing into the infant’s eyes; monkey mothers do this for about a week, then stop (staring in later life is considered a power grab). If mothers and their infants don’t do this sort of bonding (or if the mother is absent), the infants often grow up “uptight,” with continuing social troubles.
Researchers have found differences between peer-reared and mother-reared animals in behavior, blood chemistry, brain structure and function, metabolism—and their genomes, he said.
“One-fifth of the entire genome has differentiated methylation (changes caused by environment) as a function of this different experience” in an infant monkey’s first six months. “That’s 4,400 genes.”
One gene controls the amount of serotonin in the bloodstream; a shorter version puts a person at higher risk for anxiety-related behaviors while the longer version carries less risk. Among the peer-raised monkeys, many of the at-risk infants grew into fearful-behaving adults. Among the mother-reared ones, most at-risk infants did not.
“If you had a good mother, it doesn’t matter whether you have the long or short allele,” Suomi said. “Good mothers are preventing the gene from expressing.” He also suggested that what may be a genetic risk factor for offspring in bad environments might be a genetic protective factor for those in good environments. He called it the “buffering effect of good mothering. We’ve seen this same pattern in six or seven other genes” and continue to look for more.
The connection isn’t as clear in experiments with human babies; Soumi said there have been conflicting results in the work done so far. “But it is very clear in monkeys.” (Two of his earlier, hour-long lectures are available on Viddler and YouTube.)
He and colleagues now are testing interventions to see if they can improve the peer-raised monkeys’ chances of acting as good mothers for their own offspring. Extrapolating to his own species, he said, “It’s really important for mothers to be taking care of their kids, and we should be doing everything possible to help them.”
Sounds like we should invite him back for Mother’s Day.