Alcoholism and the brain: an overview

Alcohol Research & Health, Spring, 2003 by Marlene Oscar-Berman, Ksenija Marinkovic

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. KEY WORDS: neurobehavioral theory of AODU (alcohol and other drug use); alcoholic brain syndrome; brain atrophy; neuropsychological assessment; neurotransmission; risk factors; comorbidity; disease susceptibility; neuroimaging; treatment factors; survey of research

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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 alcoholism (1) on the brain and behavior, and the implications of this research for treatment.

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 (Rourke and Loberg 1996). 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 (e.g., language, reasoning, and problem-solving abilities) (Rourke and Loberg 1996). 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 (Bates et al. 2002; Gansler et al. 2000; Sullivan et al. 2000). 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 (Parsons 1996). 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 (i.e., 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 (Petrakis et al. 2002).

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 (Oscar-Berman 2000). 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 (age 50 and older) 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 (Oscar-Berman 2000).