According to Andrea C. King, a psychologist and assistant professor in the department of psychiatry at the University of Chicago, an individual's subjective responses to alcohol - meaning whether they feel alcohol's stimulating or sedating effects - may determine that individual's vulnerability to future development of alcohol-use problems.
"A person who feels enhanced euphoria and stimulation when drinking alcohol may be more likely to continue to consume alcohol during the drinking bout," said King, who is also the study's lead author. "Since they may be more sensitive to the rewarding effects of alcohol, they may be more vulnerable to developing habitual, heavy drinking patterns which would increase their chances of having eventual alcohol problems and negative consequences related to drinking."
"Alcohol works on different brain chemicals that may be more or less sensitive to various amounts of alcohol in the blood," added Raymond Anton, professor of psychiatry and scientific director of the Alcohol Research Center at the Medical University of South Carolina. "It is likely that different people have different brain chemistries, making them more or less sensitive to one or the other of these effects, stimulation or sedation, from a given dose of alcohol."
Researchers examined two distinct groups of drinkers (n=34) between the ages of 24 and 38 years, based on their typical drinking patterns during young adulthood. Light drinkers (10 males, 4 females) consumed five or less drinks total per week, typically between one to three drinks per occasion. Heavy drinkers (16 males, 4 females) reported regular consumption of 10 drinks weekly, with at least five or more drinks per occasion (4 per occasion for females), one to four times per week. Study participants received either two different doses of alcohol (the equivalent of two or four drinks) or a placebo with an alcohol smell and taste during three early evening testing sessions. At various intervals, each participant completed questionnaires and was tested for their heart rate, and blood alcohol and cortisol (a stress hormone) levels.
"The heavy drinkers showed increased stimulation and euphoria to alcohol when blood alcohol concentrations were rising," said King. "They also indicated that they liked the effects they were experiencing and wanted more of the beverage they were drinking. They only reported sedation and fatigue when blood alcohol concentrations were declining. We call this a 'biphasic' alcohol response, meaning the mood effect depended on the phase in the blood alcohol curve. In contrast, the light drinkers showed increases in alcohol sedation during both phases and they did not report stimulation or positive mood changes. In addition, they had increases in cortisol after drinking, whereas the heavy drinkers did not."
"It has been suggested that those individuals who go on to develop alcohol dependence are more likely to be less sedated by alcohol during their early - as in teenage - drinking experiences. That is, those who can 'drink their friends under the table' might be at more risk for developing increasingly heavy drinking and, later on, alcoholism. This article takes the issue one step further by suggesting that not only do heavy drinkers have more tolerance to alcohol-induced sedation but they also have more stimulation. The combination of these effects, more stimulation and less sedation, is like driving a car with a powerful engine but with faulty brakes. It is fun to drive, but may eventually get you into trouble."
Anton believes these kinds of findings can help scientists and doctors predict the development of future alcohol problems by evaluating an individual's current response to alcohol. "This work also suggests," he said, "that the difference in the biology of folks who stimulate or sedate to alcohol may be different, and that this difference may be important in understanding how alcoholism develops."
King added that heavy drinking, especially "binge drinking" where an individual consumes five or more drinks per occasion at least once weekly, continues to be a problem among young adults. "We are planning studies to continue examining this at-risk group of drinkers," she said. "After college, a proportion of heavy drinkers will 'mature out' of their binge drinking, but some will continue with hazardous drinking and eventually start to have serious consequences as a result of their drinking habits. We still don't know a lot about the mechanisms behind why some people drink heavily and others do not. We hope to examine specific alcohol-response indicators to understand those mechanisms at a brain-behavior level."
Co-authors of the Alcoholism: Clinical & Experimental Research paper included: Tim Houle, Harriet de Wit, Louis Holdstock, and Alyson Schuster of the Pritzker School of Medicine in the Department of Psychiatry at The University of Chicago. The study was funded by the Alcoholic Beverage Medical Research Foundation, and the National Institute on Alcohol Abuse and Alcoholism.