A variant of the alcohol dehydrogenase enzyme ADH1B*3 is associated with reduced rates of alcohol dependence (AD), according to a study in Alcoholism: Clinical&Experimental Research.

The enzyme variant appears to cause sedation and reduce the amount alcohol a person will drink.  ADH1B*3 is found almost exclusively in populations with African ancestry, the study's authors say.

"In one study looking at genetic samples from a number of African groups, the ADH1B*3 variant was found in almost every group," explained Denis M. McCarthy, associate professor of psychology at the University of Missouri. "Furthermore, prior studies had shown that those with ADH1B*3 had reduced drinking and risk for AD, and this was thought to be due to the different form of ADH enzyme that people with this allele have.

"The goal of our study was to see if those with ADH1B*3 had different subjective and physiological response to alcohol compared to those who do not. This would be one explanation for why they drank less than others – they have a different experience from drinking."

Researchers provided a moderate alcohol dose – 0.72 g/kg for males, 0.65 g/kg for females – to 91 African American adults (52 females, 39 males) aged 21 to 26 years. All participants were genotyped for ADH1B*3 as well as additional polymorphisms that might contribute to alcohol response. Measures such as breath alcohol concentrations (BrACs), self-reports on sedation and stimulation, and pulse rates were collected both prior to alcohol consumption as well as for 2.5 hours following consumption.

Results showed that ADH1B*3 was associated with higher levels of sedation, as well as a sharper increase in pulse rate immediately following alcohol consumption.

"The unique part of this study is showing that people with this allele have a different experience when they drink –they get more sedated, particularly when their BrAC is high," said McCarthy. "This would be one explanation for their reduced drinking behavior – people are less likely to drink heavily when doing so makes them tired rather than stimulated or disinhibited. It is important for genetic research to go beyond demonstrating that a gene is related to a drinking disorder and instead demonstrating the steps by which the gene can exert its influence on that disorder."


Citation: McCarthy et al., 'ADH1B*3 and Response to Alcohol in African-Americans', Alcoholism: Clinical and Experimental Research, May 2010; doi:10.1111/j.1530-0277.2010.01205.x