Genes appear to play a major role in whether a person experiences a blackout after heavy drinking, according to a new study from alcoholism researchers at Washington University School of Medicine in St. Louis and the Queensland Institute of Medical Research in Brisbane, Australia. Blackouts are periods of time that cannot be remembered later.
Based on those assumptions, structural equations are developed that allow the estimation of genetic and shared environmental contributions to the variance in blackouts seen among the more than 4,500 men and women surveyed.
Using those equations, Nelson’s team found that much of the risk for blackouts was genetic. The researchers also found that blackouts were more common in those who were alcohol-dependent.
“Alcoholics certainly have a higher rate of blackouts,” he says, “but blackouts also are common among non-alcoholics.”
How do genes contribute to risk for blackouts? The study did not address that issue directly, but Nelson says other research has suggested some targets.
“People who drink on an empty stomach or gulp their alcohol have higher rates of blacking out,” he says. “Therefore, less efficient variants of genes involved in metabolizing alcohol could predispose people to blackouts. We also know that alcohol has effects on systems in the brain that are involved in memory formation, so it is likely that genes whose products are components of those systems may be contributing to the risk for blackouts.”
As is the case for alcohol-dependence, Nelson says that many genes probably contribute to the risk for alcohol-related blackouts. He also expects there will be overlap between genes that contribute to risk for becoming alcoholic and genes that predispose a person to blackouts.
What’s certain is that the more a person drinks, the more likely they are to suffer blackouts or to become alcohol-dependent. Those who reported drinking to intoxication and binge drinking also were more likely to report blackouts.
“If you drink enough, you are likely to either black out or pass out,” Nelson says. “It has been reported that individuals who can drink large amounts of alcohol without passing out are predisposed to becoming alcohol-dependent and to having blackouts.”
Nelson EC, Heath AC, Bucholz KK, Madden PAF, Fu Q, Knopik V, Lynskey MT, Whitfield JB, Statham DJ, Martin NG. Genetic Epidemiology of Alcohol-Induced Blackouts. Archives of General Psychiatry, vol. 61, pp. 257-263, March, 2004.
This research was funded by the National Institute on Alcohol Abuse and Alcoholism and National Institute on Drug Abuse of the National Institutes of Health and the Australian National Health and Medical Research Council.