The DSM describes many substance-related disorders, which occur when a person is intoxicated by, withdrawing from, using, abusing, or dependent on one or more drugs. Two common types of substance-related disorders are substance abuse and substance dependence.
The DSM defines substance abuse as a maladaptive pattern of drug use that results in repeated negative consequences such as legal, social, work-related, or school-related problems. A drug abuser may even use drugs in situations in which it is physically dangerous to do so.
Substance dependence, or drug addiction, involves continuing to use a drug despite persistent physical or psychological costs. A person who is addicted to drugs may make several unsuccessful attempts to give up the drug and may even develop tolerance for the drug. Tolerance is the gradual need for more and more of the drug to get the same effect. The person may also experience withdrawal symptoms such as sweating, nausea, muscle pain, shakiness, and irritability when he or she stops taking the drug.
Many researchers believe biology and environment interact to produce substance dependence.
Several lines of research have examined genetic predispositions to drug dependence. Researchers think there may be a genetic predisposition to one particular type of alcoholism: the type that begins in adolescence and that is associated with impulsive, antisocial, and criminal behavior. With other types of alcoholism, many genes may interact to play a role.
Genes may influence traits such as impulsivity, which can make a person more likely to become alcoholic. Genes may also influence the level of dopamine in the brain. Researchers have suggested that high dopamine levels may in turn influence the susceptibility to alcoholism.
Just as biological factors may make a person susceptible to dependence, heavy use of drugs can affect a person’s biological makeup. For example, excessive drug use can reduce the number of dopamine receptors in the brain. Since dopamine is involved in feeling pleasure, the reduced number of receptors can then make a person dependent on the drug. The person will crave more of the drug in order to feel the same amount of pleasure.
Research findings suggest that certain environmental factors play a key role in substance dependence: