Alcohol's Effects on Brain : Part 2

by National Institute of Health

(Page 5 of 5)

Other studies, both in humans and in animal models, also have associated heavy episodic drinking patterns, as opposed to daily drinking patterns, with detrimental effects on cognitive functioning. These analyses also found that adolescents or young adults who are heavy episodic drinkers may be more sensitive to alcohol's harmful effects on neurocognition than those who drink less or in a more consistent pattern. Weissenborn and Duka studied 95 participants ages 18 to 34, categorizing them as nonepisodic drinkers or heavy episodic drinkers, which are defined as men who consume five drinks or more per occasion and women who consume four drinks or more. Half of the participants from each group were given alcohol (the equivalent of about four to five drinks), and the others received a placebo. When all participants were subsequently tested on memory acquisition, motor functioning, spatial working memory, pattern recognition, and spatial recognition tasks - in the presence and absence of alcohol - the heavy episodic drinkers performed significantly worse than the nonepisodic drinkers on the spatial-working-memory and pattern recognition tasks. These findings support the hypothesis that a pattern of heavy episodic drinking can be particularly harmful to cognitive functioning.

Duration of Abstinence

Studies in adult alcoholics have shown that some brain function previously damaged by alcohol can be recovered after sustained abstinence. Studies in young people suggest that at least some negative neuropsychological effects of heavy drinking persist even among drinkers who remain abstinent for extended periods of time. Brown and colleagues found that adolescents with AUDs still appeared to have reduced neuropsychological functioning after a 3-week period of abstinence, ruling out protracted withdrawal as the cause of reduced scores. However, it remains largely unknown whether full functioning returns after longer periods (e.g., 6 months to 1 year or more) of abstinence. More research is needed to determine if these consequences can reverse and whether the adolescent brain recovers from the effects of heavy alcohol use more easily than the adult brain.

Use of Other Drugs

In addition to the growing research on the neurocognitive effects5 of heavy alcohol use, researchers have evaluated how using more than one drug affects neurocognitive functioning in young people. (5 The term "neurocognitive" refers to thinking and memory abilities as determined by a variety of measures, including brain imaging, nonstandardized thinking and memory tests, and neuropsychological tests.) Grant and colleagues suggested that neuropsychological deficits were most strongly related to the heavy use of four or more drugs in addition to heavy alcohol use. These investigators concluded that heavy use of alcohol in conjunction with other drugs exacerbates the neuropsychological effects of alcohol alone among young adults. Other studies have produced different results, however, and there is tremendous variability among adolescents with respect to patterns of combining different drugs, which greatly complicates conducting studies and comparing the results. Nevertheless, it appears that using drugs such as cocaine or methamphetamine, or abusing prescription drugs in conjunction with heavy drinking, is related to poorer neurocognitive functioning.

Co-Occurring Psychiatric Disorders

Youths with AUDs are at increased risk of having other psychiatric disorders as well, such as conduct disorder, bipolar disorder, schizophrenia, and attention deficit hyperactivity disorder. At the same time, young people with psychiatric symptoms and disorders are more likely to have AUDs than are youths without psychiatric problems. In particular, conduct disorder (which is characterized by inappropriate, defiant, aggressive, or antisocial behavior in children and adolescents) is related to an increased risk of developing AOD use disorders in adolescence.

Giancola and colleagues have suggested that antisocial behavior is one of the best predictors of AOD use disorders. In their study, these investigators divided 282 female adolescents, ages 14 to 18, into two groups: an AOD use disorder group (N = 188) and a control group (N = 94) without AOD use or other psychiatric disorders. The two groups were matched on age, socioeconomic status, and intelligence. All participants were given tests measuring constructive thinking (i.e., ability to think in a manner that solves everyday problems efficiently) and executive functioning (e.g., planning, abstract reasoning, cognitive flexibility, working memory, and regulation of goal-directed behavior). The study found that the AOD use disorder group exhibited significantly poorer constructive thinking and executive functioning than did the control group. Moreover, the AOD abusers also reported a significantly higher level of antisocial behavior. Statistical analyses suggested that antisocial behavior was responsible for 77 percent of the relationship between AOD use disorder and executive functioning and for 51 percent of the relationship between AOD use disorder and constructive thinking. These results indicate that antisocial behavior is an important variable to consider when evaluating neurocognitive functioning in adolescents with AOD use disorders.

Conclusions

Recent evidence suggests that heavy drinking during adolescence and young adulthood is associated with poorer neurocognitive functioning during the young adult years, and particularly with impairment of attention and visuospatial skills. This is an important area of research because a substantial portion of the young adult population drink at potentially harmful levels. Moreover, young adulthood, especially the college years between the ages of 18 and 25, is an important period in life during which key decisions in educational, occupational, and social realms are made that can have lifelong ramifications. Therefore, solid information on the causes and consequences of alcohol use during this developmental period is needed in order to devise effective strategies to prevent alcohol-related neurocognitive impairments.

Brain imaging and studies of event-related potentials have demonstrated that heavy alcohol consumption during adolescence and young adulthood also can lead to subtle but significant abnormalities in brain structure and function. The alterations observed include reduced hippocampal volume, disturbed white-matter integrity, delayed neural response during information processing, and reduced brain response in key regions during tasks requiring working memory. These abnormalities may represent subtle early harm to brain cells and other constituents that may result from the neurotoxic effects of alcohol.

Several factors influence the likelihood that a young adult drinker would incur these adverse neurocognitive effects. For example, a drinking pattern characterized by heavy and episodic drinking to the extent that the drinker experiences unpleasant effects (i.e., hangover or withdrawal symptoms) after drinking has been associated with particularly poor cognitive functioning. Being female and having a family history of alcoholism appear to be moderately associated with additional vulnerability to the deleterious effects of heavy drinking on neurocognition, but more research is needed in order to understand these effects in young people. In addition, it is essential to consider concurrent use of other drugs and the presence of other psychiatric disorders (e.g., conduct disorder) when assessing the relationships between alcohol consumption and brain functioning. Additional longitudinal studies will lead to a better understanding of how neurocognition is affected by age at onset of an AUD, the extent to which alcohol use actually causes brain problems, and the recoverability of brain functioning with sustained abstinence. Importantly, although there is much evidence that it is indeed alcohol (rather than preexisting genetic, brain, or psychiatric factors; brain abnormalities; or psychiatric disorders) that causes the adverse neurocognitive effects observed in the studies discussed in this article, this assumption has yet to be confirmed unequivocally.

Even though the research on alcohol's effects in adolescence and young adulthood is still in its early stages, one important message is clear: Young people can help maximize their neurocognitive potential by refraining from heavy drinking.

About the Author

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