Public Release: 

Tolerance for alcohol associated with family history

Center for Advancing Health

People with a family history of alcoholism may develop a tolerance that causes them to drink more in order to feel the same effects, according to a recent study.

In a laboratory experiment, research participants who had a family history of alcoholism reported greater feelings of intoxication after 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: Their perceptions of intoxication became no different from those of the other participants.

The study's lead author, Sandra L. Morzorati, Ph.D., of the Indiana University School of Medicine, reports in the August issue of Alcoholism: Clinical and Experimental Research that the findings "suggest that the development of tolerance may maintain or increase drinking in people with a family history of alcoholism; i.e., they imbibe more to maintain the same effects."

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 who had 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. Moreover, while their breath alcohol levels were being held constant, the subjects with a family history of alcoholism adapted to the effects of alcohol. 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.

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.


The study was funded in part by the Public Health Service.

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