ScienceDaily (Nov. 10, 2007) — Females seem to be unequally disposed to the harmful effects of stress and to addiction compared with males. Recent studies show that:
- Estrogen can increase the possibility that females will start to take, and continue taking, cocaine.
- Females appear to have a genetic predisposition toward reproducing the physiological reward produced by cocaine, suggesting sex chromosomes may influence habit formation.
- Mothers with post-traumatic stress disorder (PTSD) may uniquely pass on biological risk factors to their offspring, according to work with the descendents of Holocaust survivors.
- Stress can damage an area of the brain with a controlling effect on mood.
- Females without a growth-factor gene can become more depressed than males.
"The comparisons between male and female responses to pain, depression, injury, and addiction are manifold," says Bruce McEwen, PhD, at Rockefeller University in New York City. "Neuroscientific proof of these differences can have profound impacts on everything from over-the-counter pharmaceuticals to government reimbursements for health care."
In three experiments with rats, Jill Becker, PhD, of the University of Michigan, found in each case that females showed an increased vulnerability to cocaine addiction.
In the study, a pool of 150 male and female rats of various predetermined hormone levels (some males were castrated, some females had their ovaries removed) were exposed to various combinations of estrogen, progesterone, or a peanut oil control. The rats were allowed to self-administer cocaine for a three-week period, during which time doses increased every seven days.
Becker found that female rats were more likely to use cocaine when circulating estrogen was high, but also that progesterone could counter the effects of estrogen. Further, she found that the administration of estrogen had no effects on self-administration in male rats.
"The factors that cause some people to try drugs despite all of society's warnings about their dangers are complex, but we know that among the factors are gender, personality type, and prior stress experiences," Becker says. "Women tend to try cocaine earlier in life, susceptible individuals become addicted faster, and, once addicted, they suffer worse damage to their brains, hearts, and livers as a result of their cocaine use, compared with men."