Adolescence is often a time of fashion consciousness, learning how to drive a car, and exploring the limits of parental patience and endurance. Adolescence is also a time when most people begin drinking, often drink the most, and for some, experiment with binge drinking. A study in the August issue of Alcoholism: Clinical & Experimental Research (ACER) explores the long-term neurobehavioral consequences of binge drinking during adolescence.
Binge drinking can be loosely defined as an intense bout of drinking during a single session, such as a single evening. For males, that can mean five or more drinks in one sitting; for females, it can be four or more drinks. Several studies have found that a significant percentage of teenagers report regular bouts of drinking in which high blood alcohol levels are attained. Furthermore, when the above definitions are used, recent data from the Harvard School of Public Health College Alcohol Study indicates that roughly 45 percent of all college students binge drink. According to Aaron M. White, research associate in the department of psychiatry at Duke University Medical Center and first author of the ACER study, roughly 23 percent of all college students are frequent binge drinkers, meaning that they binge three or more times in a two-week period.
White and his co-authors used rodents to test for the effects of binge-pattern drinking. "We were particularly interested in knowing whether these treatments produced different effects in younger rats than in older rats," he said.
After a regimen essentially comparable to multiple instances of binge drinking in humans, both adolescents and adults were tested for anxiety and learning. Following the initial alcohol exposure phase, no effects were found. However, when a later, moderate dose of alcohol was given to all of the rats, those that had previously received the adolescent alcohol exposure showed the greatest disruption of working memory. These results suggest that binge-pattern exposure to alcohol during adolescence does something to the adolescent brain that leads it to respond differently - more sensitively - to alcohol in the future.
"We believe that the adolescent brain is more vulnerable to the neurotoxic effects of alcohol than the adult brain," White explained, "and this could account for the findings of our study. Alcohol impairs activity at a receptor called the NMDA receptor. These receptors are highly concentrated in the hippocampus, a brain region critically involved in learning and memory. During withdrawal from alcohol, NMDA receptors can become overly active, which can make the brain more vulnerable to cell death. We are currently investigating whether adolescent brains exhibit greater withdrawal-induced hyperactivity at NMDA receptors than adults, and if such hyperactivity leads to greater cell death in adolescent than adult subjects."
"The implications of this study," said David L. McKinzie, senior biologist at Lilly Research Laboratories and adjunct assistant professor at the Indiana University School of Medicine, "are that teenagers who drink heavily and often may be especially susceptible to the neurobehavioral effects of alcohol than would adults with similar drinking experiences. Of special concern is the possibility that the effects of early chronic alcohol drinking may have long-lasting consequences, both as a general insult to the brain as well as changing the individual’s later reactivity to alcohol."
Although White cautioned against generalizing from a small sample of rats to the entire human population, he noted that the findings are consistent with previous research on alcohol abuse during adolescence. McKinzie concurred.
"The few animal studies to date have consistently suggested that developing brains are especially sensitive to the toxic effects of alcohol," said McKinzie. "This type of study is particularly important because a large percentage of adolescents consume alcohol. Unfortunately, relatively little is know about the long-term consequences of chronic alcohol drinking in adolescent individuals. If this age group is indeed found to be especially vulnerable to alcohol and its long-term effects, as this study suggests, we may need to concentrate our efforts on preventive strategies."