Adolescent Brain and Alcohol Effects

by National Institute of Health

Many people begin to drink alcohol during adolescence and young adulthood. Alcohol consumption during this developmental period may have profound effects on brain structure and function. Heavy drinking has been shown to affect the neuropsychological performance (e.g., memory functions) of young people and may impair the growth and integrity of certain brain structures. Furthermore, alcohol consumption during adolescence may alter measures of brain functioning, such as blood flow in certain brain regions and electrical brain activities. Not all adolescents and young adults are equally sensitive to the effects of alcohol consumption, however. Moderating factors - such as family history of alcohol and other drug use disorders, gender, age at onset of drinking, drinking patterns, use of other drugs, and co-occurring psychiatric disorders - may influence the extent to which alcohol consumption interferes with an adolescent's normal brain development and functioning.

Several decades of research have shown that chronic heavy drinking is associated with adverse effects on the central nervous system and have revealed some of the processes that give rise to these effects. Yet it remains unclear when in the course of a person's "drinking career" these central nervous system changes may emerge. Recent research suggests that heavy drinking may already affect brain functioning in early adolescence, even in physically healthy youths. This issue is important and interesting for at least two reasons. First, the brain continues to develop throughout adolescence and into young adulthood, and insults to the brain during this period therefore could have an impact on long-term brain function. Consistent with this assumption, animal studies have demonstrated that alcohol exposure during adolescence and young adulthood can significantly interfere with an animal's normal brain development and function. Second, young adulthood is a period when most people make critical educational, occupational, and social decisions, and impaired cognitive functioning at this time could substantially affect their futures.

Questions regarding alcohol's influence on brain development and function during adolescence are especially pertinent because heavy drinking is quite common among young people. For example, in one survey, 36 percent of 19- to 28-year-olds reported having consumed five or more drinks in a row in the preceding 2 weeks. Another survey determined that 7 percent of 18- to 25-year-olds meet the diagnostic criteria for alcohol dependence. Thus, a substantial number of adolescents and young adults could be at risk for alcohol-related impairment of brain development and brain function.

This article reviews research on the impact of alcohol on the brains of young adults. It discusses several areas of brain function and development that appear to be affected, describes the extent of the harm observed as well as the factors that appear to moderate alcohol's effects, and identifies high-risk groups of youths who are most likely to incur alcohol-related brain impairment.

Effects on Neuropsychological Performance

One aspect of brain functioning that is commonly studied in youths as well as older adults is neuropsychological performance,1 which includes memory function, attention, visuospatial skills, and executive functioning (e.g., planning, abstract reasoning, and goal-directed behavior). Several studies have suggested that heavy alcohol use in young people appears to be associated with potentially long-term deleterious effects on neuropsychological functioning.

Brown and colleagues studied 33 alcohol-dependent adolescents, ages 15 and 16, who were in treatment for dependence on alcohol but not on other drugs. These teens had used alcohol an average of 753 times in their lives. A control group (N = 24) who had no history of alcohol and other drug (AOD) problems were matched with the alcohol-dependent adolescents on age, gender, socioeconomic status, education, and family history of AOD problems. Both groups of participants were given neuropsychological tests after 3 weeks of abstinence. The investigators found that the alcohol-dependent adolescents performed worse on tests of verbal and nonverbal memory than the control adolescents. They also found that alcohol-dependent adolescents who reported a greater number of alcohol withdrawal symptoms demonstrated poorer visuospatial functioning.

These findings were supported by a long-term study of 115 adolescents with AOD use disorders. The participants, ages 13 to 18 (average age, 16) at the beginning of the study, were recruited after completing inpatient treatment for AOD use disorders and were initially followed for 4 years. At the 4-year followup, the participants were divided into three groups based on their AOD use at followup:

Nonabusers (N = 32) who had experienced no further AOD-related problems after the initial treatment.

Abstinent abusers (N = 38) who had resumed harmful AOD use after treatment but had been abstinent for the 28 days prior to followup (or longer).

Active abusers (N = 45) who had resumed harmful AOD use after treatment and had used AODs in the 28 days prior to followup.

The three groups were similar with respect to demographic characteristics (e.g., age, ethnicity, and family history of AOD problems), except that the active abuser group included more males.

In addition to drinking and drug use behavior, the investigators assessed the number of different withdrawal symptoms reported by the participants at the 4-year followup. Abstinent abusers (i.e., those who had been abstinent for the 28 days prior to assessment) reported an average of 1.4 different withdrawal symptoms, compared with an average of 3.1 different withdrawal symptoms reported by active abusers.

Directly after recruitment into the study, the groups had shown no significant differences on any of the neuropsychological measures assessed. At the 4-year followup, however, the abstinent and active abusers performed worse than the nonabusers on attention tasks, with the active abusers exhibiting the worst performance. In addition, participants who reported more withdrawal symptoms during the previous 3 months showed poorer visuospatial abilities, even when gender, history of head injury, history of a learning disability, number of grades completed, and socioeconomic status were considered. This latter observation suggests that the number of different alcohol withdrawal symptoms may be an important indicator of the degree of later alcohol-related cognitive impairment, at least among AOD-dependent young adults. Alcohol withdrawal symptoms were equally predictive of neuropsychological problems in alcohol-dependent as well as other-drug-dependent youths (although almost all drug-dependent youths were also alcohol dependent).

A continuation of this study evaluated participants 8 years after initial recruitment into the study. These analyses confirmed that lifetime history of alcohol withdrawal symptoms predicted cognitive performance, especially on visuospatial tests - that is, young people who had experienced a greater number of withdrawal symptoms performed worse on visuospatial tasks than did young people who had had fewer withdrawal symptoms.

Although these studies clearly have demonstrated that heavy alcohol use during adolescence and young adulthood is associated with poorer neuropsychological functioning, these impairments in young adults with alcohol use disorders (AUDs) (i.e., alcohol abuse and dependence) appear to be generally mild. For example, Eckardt and colleagues assessed neuropsychological functioning in 101 males, ages 18 to 35, with AUDs. This study found that almost all participants performed within the average range across tests. Nevertheless, young people who had consumed more alcohol throughout their lives performed more poorly, and young people who had abstained from alcohol for a longer time performed better. The investigators also noted that the study participants had experienced alcohol-related problems only for relatively short periods of time, which may contribute to the relatively mild impairment seen. But even if neuropsychological impairments generally are not severe, they represent a serious public health concern, considering how prevalent heavy drinking and alcohol-related problems are in young adults.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.