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The more alcoholic relatives a person has, the more they need to drink to feel alcohol's effects

July 25, 2006

Genes contribute between 50 and 60 percent to the heritability of alcoholism.

- A low level of response (LR) to alcohol is an important component of how a family history of alcoholism conveys a person's greater risk of developing alcoholism him or herself.

- New findings indicate that the more alcoholic relatives a person has, the lower their LR will likely be.

Alcoholism is genetically influenced, and a low level of response (LR) to alcohol is one of several known risk factors. An individual with a low LR to alcohol, for example, generally needs more drinks to achieve a desired "buzz" from alcohol very early in his or her drinking career. New findings indicate that the more alcoholic relatives a person has, the lower their LR will likely be.

Results are published in the August issue of Alcoholism: Clinical & Experimental Research.

"The conclusion that alcoholism is genetically influenced is supported by the fact that it runs in families, with a high risk for the offspring even if they are adopted away early in life," said Marc A. Schuckit, director of the Alcohol Research Center, Veterans Affairs San Diego Healthcare System, professor of psychiatry at the University of California, San Diego, and first author of the study. "A whole host of different things seem to be responsible for how the family history of alcoholism predicts the development of alcoholism. Two examples of what is being passed down in families to increase the risk of alcoholism are high levels of impulsivity, and a low response to alcohol."

"While it is well known that a family history of alcoholism is a very strong predictor of future alcohol-related problems," agreed Victor Hesselbrock, professor of psychiatry at the University of Connecticut School of Medicine, "the components of a family history that actually convey this risk are not well known. Dr. Schuckit's study helps us begin to understand some of the critical aspects of a family history of alcoholism that increases a person's susceptibility for developing alcohol-related problems. While the amount of variance explained by LR is not large, neither is it trivial. Likely, a person's level of risk for developing alcohol problems is composed of a variety of behavioral, environmental, and genetic factors-with each contributing a small but important portion to the variance."

For this study, researchers used data gathered from 376 males during 20 years of follow-up personal interviews after entering the initial San Diego Prospective Study. During the first stage of the study, alcohol challenges were used to establish LR when the participants were approximately 20 years of age; about half had at least one alcoholic relative. Follow-up interviews were conducted at 10, 15 and 20 years after the initial evaluation. Researchers analyzed the relationships among the LR to alcohol, the family history (FH), and five alcohol-related outcomes: maximum quantity of alcohol consumed since original testing, maximum frequency, nondiagnostic alcohol-related problems, number of applicable Diagnostic and Statistical Manual of Mental Disorders abuse and dependence items, and the presence or absence of an alcohol-use disorder.

"We found that first, both FH and low LR to alcohol relate to a variety of alcoholic outcomes," said Schuckit. "Second, they relate to these alcoholic outcomes even when considered together in statistical analyses, each adding something unique. Third, low LR to alcohol is actually a better predictor than FH for high levels of drinking per occasion, whereas FH is a bit better than the narrow concept of low LR in predicting a wide pattern of problems."

"These findings indicate that LR contributes separately to the prediction of levels of drinking and to the likelihood of developing alcohol-related problems," said Hesselbrock. "FH, on the other hand, does not apparently influence usual consumption levels but does contribute to the susceptibility for developing alcohol problems in adulthood. Why is this important?," he asked. Because of its potential for intervention, and even prevention, he answered.

"While we have known for a long time that the best predictor of future problems is having a family history of alcoholism," Hesselbrock continued, "this does not provide information that is particularly relevant for prevention or intervention. However, Dr. Schuckit's findings help show that LR can be reliably measured, is heritable, and contributes to the prediction of a variety of adult outcomes that can lead to an alcohol use disorder. As a measurable trait, it could then be assessed in a clinical situation. Importantly, low LR could be modified using psychotherapeutic methods or possibly pharmacologically for individuals engaged in unhealthy heavy drinking. Further, Dr. Schuckit's previous work has suggested that LR can be adequately assessed via questionnaire among individuals who have just begun their drinking career. Assessment of LR in this way might be used to identify individuals at particularly high risk for developing alcohol-related problems; and these individuals could be targeted for prevention efforts."

"Every research project is one small step," added Schuckit. "What we're really trying to do is identify people at risk so that we can develop prevention techniques that are more effective. Maybe one day we will know enough to be able to take the kids who are at risk, even before they drink their first drink, and help them. The aim of all that I do is prevention."

Alcoholism: Clinical & Experimental Research