Alcohol and Other Drugs

… as reported by the US Department of Health and Human Services, National Institutes of Health, and National Institute on Alcohol Abuse and Alcoholism – ALCOHOL ALERT, Number 76, July 2008:

Drug and alcohol dependence often go hand in hand. Research shows that:

  • people who are dependent on alcohol are much more likely than the general population to use drugs, and
  • people with drug dependence are much more likely to drink alcohol.

For example, one study found that, of 248 alcoholics seeking treatment, 64 percent met the criteria for a drug use disorder at some point in their lifetime. Patients with co-occurring alcohol and other drug use disorders also are likely to have more severe dependence-related problems than those without combined disorders—that is, they meet a higher number of diagnostic criteria for each disorder (three out of seven criteria are required to meet the diagnosis of dependence).

People with co-occurring alcohol and other drug use disorders are more likely to have psychiatric disorders such as personality, mood, and anxiety disorders; they are more likely to attempt suicide and to suffer health problems. People who use both alcohol and drugs also are at risk for dangerous interactions between these substances. For example, a person who uses alcohol with benzodiazepines, whether these drugs are prescribed or taken illegally, is at increased risk of fatal poisoning.

This writing represents some of the latest research on alcohol and other drug use disorders, examining the frequency with which these disorders occur and overlap, evidence for common genetic risk factors, and how co-occurring disorders can be most effectively diagnosed and treated.

How common is alcohol and other drug use, and how often do alcohol and drug use disorders co-occur? To answer these questions, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) conducted the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), one of the largest surveys of its kind ever performed. It examined the prevalence of alcohol and other drug use and abuse in the United States. According to NESARC, 8.5 percent of adults in the United States met the criteria for an alcohol use disorder, whereas 2 percent met the criteria for a drug use disorder and 1.1 percent met the criteria for both. People who are dependent on drugs are more likely to have an alcohol use disorder than people with alcoholism are to have a drug use disorder. Young people ages 18–24 had the highest rates of co-occurring alcohol and other drug use disorders (see figure). Men were more likely than women to have problems with alcohol, drugs, or the two substances combined.

THE GENETICS OF ALCOHOL AND OTHER DRUG USE DISORDERS—SHARED RISK FACTORS?

Research has established that some of the risk for addiction to both drugs and alcohol is inherited. Children of alcoholics are 50 to 60 percent more likely to develop alcohol use disorders than people in the general population. Similarly, children of parents who abuse illicit drugs may be 45 to 79 percent more likely to do so themselves than the general public. This suggests that some of the risk factors for alcohol and other drug use are rooted in genetics, though studies of specific families have not proven a genetic contribution.
Researchers believe that some of the same genes that increase a person’s risk for problems with alcohol also might put him or her at greater risk for drug dependence. Moreover, those same genes might increase the risk for other psychiatric problems, such as conduct disorder and adult antisocial behavior (i.e., externalizing behaviors).

Much of the most compelling evidence for this apparent genetic link is based on twin and adoption studies.1 For example, in 2003, Kendler and colleagues analyzed data from the Virginia Twin Registry. They compared rates of alcohol, drug, and other externalizing disorders in identical and fraternal twins. They found that, in identical twins, when one twin was dependent on alcohol or on drugs, the second twin was much more likely (than a second fraternal twin) to have a problem with drugs or alcohol or to have an externalizing disorder. The study suggested that certain genes put people at risk for both alcohol and other drug use disorders, as well as externalizing disorders, whereas other genes put people at risk for specific types of disorders. These disorder-specific genes often are linked to how the body breaks down (or metabolizes) specific drugs and alcohol.
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1Adoption studies compare the risk of alcoholism in biological relatives with the risk in adoptive relatives of alcoholics (e.g., an adopted-away child of an alcoholic parent). Twin studies compare the risk of alcoholism in pairs of twins reared in the same environment, examining both identical twins (i.e., twins who share 100 percent of their genes) and fraternal twins (i.e., twins who share, on average, only 50 percent of their genes).