In a laboratory experiment, research participants who had a family history of alcoholism reported greater feelings of intoxication after initial exposure to alcohol than participants who did not have a family history of alcoholism. But those with a family history of the disease quickly adapted to the alcohol and their perceptions of intoxication became no different from those of the other participants.
"This suggests that the development of tolerance may maintain or increase drinking in people with a family history of alcoholism. In other words, they imbibe more to maintain the same effects," says the study's lead author, Sandra L. Morzorati, associate scientist in the Department of Psychiatry at the IU School of Medicine.
Dr. Morzorati noted that previous efforts to compare the responses to alcohol among subjects with different family histories have yielded inconsistent results, which may result from individual variations in the brain's exposure to alcohol over time, as well as differences in the way subjects absorb and eliminate alcohol.
This study differs from earlier research because it used a method called the "breath-alcohol level clamp" to keep subjects' breath-alcohol levels constant throughout the experiment. The study looked at 58 people with a family history of the disease and 58 with no known family history, all of whom were social drinkers between ages 21 and 39. The groups were evenly divided by gender and had comparable demographic characteristics and alcohol consumption rates.
Each participant was tested twice - once with alcohol, once with placebo - at least a week apart. In the alcohol session, participants received an intravenous infusion of alcohol. In the placebo session, they received an intravenous infusion without alcohol. At an initial measurement, participants with a family history of alcoholism reported greater feelings of intoxication than their counterparts, the IU researchers found.
"Moreover, while their breath alcohol levels were being held constant, the subjects with a family history of alcoholism adapted to the effects of alcohol," says Dr. Morzorati. "By the final measurement point, their perceptions of intoxication were comparable to those of their counterparts, indicating that the family history subjects had developed what is known as acute tolerance to alcohol."
Dr. Morzorati noted that the study was based on the premise that increased risk for alcoholism is related to genetic factors underlying individual responses to alcohol consumption. These results, she said, provide additional support for that premise.
Co-authors of the IU School of Medicine study are Vijay Ramchandani, Ph.D., assistant professor and scientist; Leah Flury, M.S., applied statistician; Ting-Kai Li, M.D., distinguished professor; and Sean O'Connor, M.D., associate professor.
The study was funded in part by the U.S. Public Health Service.