Introduction
Drugs are an integral part of everyday life for many people, and drug use among adolescents remains high (see Section 23, Chapter 271). The legality and social acceptance of a particular drug often depend on what it is used for, what its effects are, and who is using it. For example, use of marijuana for pleasure is illegal and considered socially unacceptable by many people, but use of marijuana to relieve nausea in a person with advanced cancer has been legalized by some governments and is viewed as acceptable by some people. The legality and social acceptance of a drug often vary among different societies or countries. Legality and acceptance may also change within a society or country over time, as has happened with alcohol in the United States.
Many drugs, some legal and some not, alter the mind. Some mind-altering drugs affect brain function each time they are used, regardless of how much is used. Other mind-altering drugs affect brain function only if a large amount is used or if it is used continually. Some drugs affect the brain in such a way that a person wants or feels a need to use the drug again and again (craving).
Doctors may suspect problems created by the use of mind-altering drugs when they notice changes in mood or behavior. Specific questions may then be asked about potential consequences of prolonged use of specific drugs. Blood and urine tests are sometimes used to confirm suspicions that a person has been taking certain mind-altering drugs.
The problems created by use of mind-altering drugs are given many different terms, for example, drug abuse, drug dependence, and drug addiction. Doctors and other experts, in treating these problems, often disagree about the exact meaning of these terms.
Drug Abuse: Drug abuse is the use of a mind-altering drug without medical need, in an amount large enough or over a period long enough to threaten the quality of life or health and safety of the user or others. Many people use drugs without medical need but keep that use under control so that it does not threaten their health or adversely affect their functioning.
Taking a drug that does not usually alter the mind is still considered abusive if the drug is taken without medical need and if the drug endangers the quality of life or health and safety of the user or others. Drug abuse occurs in all socioeconomic groups and involves highly educated and professional people as well as those who are uneducated and unemployed.
Overdose of a drug may occur as part of abuse. With some drugs, an overdose may be profoundly frightening or even fatal.
 See the sidebar Other Drugs of Abuse.
Drug Dependence: Drug dependence is a compelling need to continue taking a mind-altering drug to induce pleasure or to relieve anxiety and tension and avoid discomfort. Drug dependence is caused by a combination of biologic and psychologic factors. Drugs that cause dependence may produce euphoria, feelings of increased mental and physical ability, and altered sense perceptions.
Dependence can be very powerful and difficult to overcome. The body adapts to the continuous use of a drug that produces dependence, leading to tolerance and to withdrawal symptoms when use stops. Tolerance is the need to use progressively larger amounts of a drug to reproduce the effects originally achieved with the starting amount.
Withdrawal symptoms occur when drug use is stopped or when the drug's effects are blocked by another drug. A person undergoing withdrawal feels sick and may develop headaches, diarrhea, or shaking (tremors). Withdrawal can evoke a serious and even life-threatening illness.
Drug Addiction: Drug addiction is the disruptive behavior or activity associated with obtaining and using a drug that a person is dependent on. Addiction generally interferes with the ability to work, study, or interact normally with family and friends. A person can become dependent on illegal drugs or legal ones and can become dependent when a drug is used for a medical need or for less acceptable reasons. However, the behavior or activity associated with obtaining and using a drug is likely to vary tremendously based on the legality and acceptance of that drug. Obtaining a legal drug to meet a medical need is often as unremarkable as going to the doctor, getting a prescription, and then going to the pharmacy. However, for an illegal drug or a legal drug used without medical need and for unacceptable reasons, the behavior or activity may include lying and stealing.
When a person with advanced cancer becomes dependent on an opioid drug such as morphine, his behavior is not usually considered an addiction. However, when a person dependent on, for example, heroin steals to have money to buy heroin and lies to family and friends about his whereabouts or what he is doing, his behavior is considered an addiction.
At times, family members or friends may behave in ways that allow an addict to continue to use drugs or alcohol; these people are called enablers (also referred to as codependents when their own needs are intertwined with perpetuating the addict's use of his addictive substance). Enablers may call in sick for an addict or make excuses for the addict's behavior. The enabler may plead with the addict to stop using drugs or alcohol but rarely does anything else to help the addict change his behavior.
A pregnant addict exposes her fetus to the drugs she is using. Often, a pregnant addict does not admit to her doctor that she is using drugs or alcohol. The fetus may become dependent and may develop serious defects as a result of the mother's drug use (see Section 23, Chapter 265). Soon after delivery, the newborn can experience severe or even fatal withdrawal, particularly when the doctor has not been informed of the mother's addiction.
| 
