Addiction

Addiction, habitual repetition of excessive behavior that a person is unable or unwilling to stop, despite its harmful consequences. People can be physically addicted to a drug, meaning they may suffer ill physical effects if they stop taking the drug. They also can be psychologically addicted to drugs, gambling, or other behaviors, meaning they feel overwhelmingly deprived if they attempt to stop.

Drug Dependence

Drug Dependence, psychological and sometimes physical state characterized by a compulsion to use a drug to experience psychological or physical effects. Drug dependence takes several forms: tolerance, habituation, and addiction.

Tolerance, a form of physical dependence, occurs when the body becomes accustomed to a drug and requires ever-increasing amounts of it to achieve the same pharmacological effects. This condition is worsened when certain drugs are used at high doses for long periods (weeks or months), and may lead to more frequent use of the drug. However, when use of the drug is stopped, drug withdrawal may result, which is characterized by nausea, headaches, restlessness, sweating, and difficulty sleeping. The severity of drug withdrawal symptoms varies depending on the drug involved.

Habituation, a form of psychological dependence, is characterized by the continued desire for a drug, even after physical dependence is gone. A drug often produces an elated emotional state, and a person abusing drugs soon believes the drug is needed to function at work or home.

Addiction is a severe craving for the substance and interferes with a person’s ability to function normally. It may also involve physical dependence.

Scientists often measure a drug’s potential for abuse by conducting studies with laboratory animals. Drugs that an animal administers to itself repeatedly are said to have powerful reinforcing properties and a high potential for abuse. These drugs include some commonly abused substances like opium, alcohol, cocaine, and see barbiturates. Other drugs, such as marijuana and the hallucinogens (see Psychoactive Drugs), appear to produce habituation in humans even though they are not powerful reinforcers for laboratory animals.

The drugs that are commonly abused, except alcohol and tobacco, can be grouped into six classes: the opioids, sedative-hypnotics, see stimulants, hallucinogens, cannabis, and inhalants.