Jan. 5, 2005 - Women are more vulnerable to many of alcohol's adverse effects than men, but new research suggests that in at least one respect they are less so.
Animal studies conducted by researchers at Duke University show that female rats are less sensitive than males to alcohol's sedating effect. The findings may help explain why fewer women than men become alcoholics, says the study's researcher.
"Women are only half as likely as men to develop alcohol abuse problems," Duke professor of psychiatry Scott Swartzwelder, PhD, tells WebMD. "There are probably many reasons for this, including the fact that drinking is more socially acceptable for men than for women. But it may also be that the female brain is less sensitive to one of the main attractive effects of this drug."
Gender and Alcohol
It is clear that when it comes to drinking alcohol, men and women are not created equal.
Women achieve higher concentrations of alcohol in the blood and become more impaired than men after drinking equivalent amounts of alcohol. The fact that women tend to weigh less than men is a big reason for this, but not the only one.
In the report, experts speculated that gender-related differences in brain chemistry and hormones may play a role in the effects of alcohol.
Behavior and the Brain
The Duke research team conducted both behavioral and brain chemistry studies on male and female adolescent and adult rats in an effort to better understand these differences. Their findings are published in the January issue of the journal Alcoholism: Clinical and Experimental Research.
Swartzwelder and colleagues reported that adolescent rats were less vulnerable to the sedative effects of alcohol than adult rats. There was no significant difference between the adolescent male and female rats.
They found that the female rats were less sensitive than the males to the sedative effects of the alcohol.
After getting the animals drunk in the name of science, Swartzwelder and researcher Young May Cha placed them on their side and measured their ability to stand up again -- an accepted measure of consciousness in animal studies known as the "righting reflex."
In a separate study, the researchers looked at alcohol's impact on the part of the brain that is activated in response to alcohol. They found that brain cells from female rats promoted less activity in this region than cells from male rats.
"This paralleled our behavioral findings," Swartzwelder says. "It shows at a cellular level that when it comes to alcohol's basic ability to promote sedation, females are less sensitive."
Drinking and Hormones
The researchers also found that the female rats showed slight differences in susceptibility to the sedating effects of alcohol at different points in their reproductive estrous cycle, which corresponds to a human female's menstrual cycle.
Many women believe that hormonal changes at different times during their menstrual cycle affect their response to alcohol, but Swartzwelder says the Duke findings do not appear to back this up.
"Cycle stage had a slight impact, but it didn't make a substantial difference," he says. "Independent of cycle stage, females were less sensitive to the sedating effect of alcohol."
He says the findings do suggest that, like adolescents, females need to be especially cautious about assessing their level of impairment while drinking.
Swartzwelder says that adolescents, especially, may be particularly vulnerable because they are less sedated by alcohol but tend to be more susceptible to other alcohol-related cognitive impairments than adults. They also tend to binge drink more.
"Adolescents are more likely to drink 10 beers in a row twice a week, while adults are more likely to have a drink or two every night," he says. "If adolescents feel less sleepy after drinking, they may be more inclined to drive or do other things they shouldn't be doing. What you have is an awake, drunk kid with poor judgment, and that is exactly what you don't want."