Alcoholism and the Brain

by National Institute of Health

Alcoholism can affect the brain and behavior in a variety of ways, and multiple factors can influence these effects. A person's susceptibility to alcoholism-related brain damage may be associated with his or her age, gender, drinking history, and nutrition, as well as with the vulnerability of specific brain regions. Investigators use a variety of methods to study alcoholism-related brain damage, including examining brains of deceased patients as well as neuroimaging, a technique that enables researchers to test and observe the living brain and to evaluate structural damage in the brain.

The brain, like most body organs, is vulnerable to injury from alcohol consumption. The risk of brain damage and related neurobehavioral deficits varies from person to person. This article reviews the many factors that influence this risk, the techniques used to study the effects of alcoholism1 on the brain and behavior, and the implications of this research for treatment. (1 Alcohol dependence, also known as alcoholism, is characterized by a craving for alcohol, possible physical dependence on alcohol, an inability to control one's drinking on any given occasion, and an increasing tolerance to alcohol's effects.

About half of the nearly 20 million alcoholics in the United States seem to be free of cognitive impairments. In the remaining half, however, neuropsychological difficulties can range from mild to severe. For example, up to 2 million alcoholics develop permanent and debilitating conditions that require lifetime custodial care. Examples of such conditions include alcohol-induced persisting amnesic disorder (also called Wernicke-Korsakoff syndrome) and dementia, which seriously affects many mental functions in addition to memory (language, reasoning, and problem-solving abilities). Most alcoholics with neuropsychological impairments show at least some improvement in brain structure and functioning within a year of abstinence, but some people take much longer. Unfortunately, little is known about the rate and extent to which people recover specific structural and functional processes after they stop drinking. However, research has helped define the various factors that influence a person's risk for experiencing alcoholism-related brain deficits, as the following sections describe.

Risk Factors and Comorbid Conditions
That Influence Alcohol-Related Brain Damage

Alcoholism's effects on the brain are diverse and are influenced by a wide range of variables. These include the amount of alcohol consumed, the age at which the person began drinking, and the duration of drinking; the patient's age, level of education, gender, genetic background, and family history of alcoholism; and neuropsychiatric risk factors such as alcohol exposure before birth and general health status. Overall physical and mental health is an important factor because comorbid medical, neurological, and psychiatric conditions can interact to aggravate alcoholism's effects on the brain and behavior. Examples of common comorbid conditions include: medical conditions such as malnutrition and diseases of the liver and the cardiovascular system. Neurological conditions such as head injury, inflammation of the brain (encephalopathy), and fetal alcohol syndrome (or fetal alcohol effects). Psychiatric conditions such as depression, anxiety, post-traumatic stress disorder, schizophrenia, and the use of other drugs.

These conditions also can contribute to further drinking.

Models for Explaining Alcohol-Related Brain Damage

Some of the previously mentioned factors that are thought to influence how alcoholism affects the brain and behavior have been developed into specific models or hypotheses to explain the variability in alcoholism-related brain deficits. The accompanying table lists the prevailing models. It should be noted that the models that focus on individual characteristics cannot be totally separated from models that emphasize affected brain systems because all of these factors are interrelated. Several of the models have been evaluated using specialized tests that enable researchers to make inferences about the type and extent of brain abnormalities.

Models Based on Characteristics of Individual Alcoholics

Premature Aging Hypothesis. According to this hypothesis, alcoholism accelerates natural chronological aging, beginning with the onset of problem drinking.

An alternate version suggests that older patients are especially susceptible to the cumulative effects of alcoholism, and aging is accelerated only later in life. The preponderance of scientific evidence suggests that although alcoholism-related brain changes may mimic some of the changes seen in older people, alcoholism does not cause premature aging. Rather, the effects of alcoholism are disproportionately expressed in older alcoholics.

Gender. Although it has been hypothesized that women's brain functioning is more vulnerable to alcoholism than men's, studies of gender differences have not consistently found this to be true, even though women and men metabolize alcohol differently (women achieve higher blood alcohol contents [BACs] than men after consuming the same amount of alcohol). However, it is not known whether this comparison between men and women holds among older populations.

Family History. Family history of alcoholism has been found to be important because it can influence such things as tolerance for alcohol and the amount of consumption needed to feel alcohol's effects. Also, studies examining brain functioning in people with and without a positive family history of alcoholism have shown that there are clear differences between the groups on measures of brain electrical activity.

Vitamin Deficiency. Research on malnutrition, a common consequence of poor dietary habits in some alcoholics, indicates that thiamine deficiency (vitamin B1) can contribute to damage deep within the brain, leading to severe cognitive deficits. The exact location of the affected parts of the brain and underlying neuropathological mechanisms are still being research.

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.