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Overview of Drug Abuse

By Patrick G. O’Connor, MD, MPH

Drugs are an integral part of everyday life for many people—legitimately and illegitmately—and drug use among adolescents remains high (see Substance Use and Abuse in Adolescents).

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, many abused drugs have legitimate medical uses:

  • Amphetamines: To treat attention-deficit/hyperactivity disorder

  • Barbiturates and benzodiazepines: To treat anxiety and insomnia

  • Cocaine: To numb surfaces of the body (as a topical anesthetic)

  • Ketamine: To provide anesthesia

  • Marijuana: To treat nausea due to advanced cancer

  • Opioids: To relieve pain and provide anesthesia

However, use of these drugs for pleasure is illegal and dangerous. 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 happened with alcohol in the United States.

Many drugs, some legal and some not, alter the mind. Some mind-altering (psychoactive) drugs affect brain function each time they are used, regardless of how much is used. Others affect brain function only if a large amount is used or if the drug is used continually. Some drugs affect the brain in such a way that people want or feel a need to use the drug again and again (craving). Some cause symptoms, such as euphoria (a high).

Narcotics are often thought of when drug abuse is discussed. This term refers to drugs that cause loss of feeling, a sense of numbness, and drowsiness. The term often refers specifically to opioids (drugs that bind to opiate receptors on cells). However, the term narcotics is also used in a broader (and inaccurate) sense to include any drug that is illegal or used illegitimately.

Did You Know...

  • Some people who abuse drugs are not dependent on them.


Different terms are used to indicate the problems caused by using mind-altering drugs. However, doctors and other experts sometimes disagree about the exact meaning of these terms.


This term means that people need more and more of a drug to feel the effects originally produced by a smaller amount. People can develop tremendous tolerance to drugs such as opioids and alcohol.


This term refers to the immediate and temporary effects of a specific drug. When people are intoxicated, mental function and judgment are impaired, and mood may be altered. Depending on the drug, people may feel a sense of excitement, an exaggerated feeling of well-being, or euphoria, or they may feel more calm, relaxed, and sleepy. Many drugs impair physical functioning, with decreased coordination, leading to falls and vehicle crashes. Some drugs trigger aggressive behavior, leading to fighting. As larger amounts of the drug are used, adverse effects become more obvious (called an overdose), with serious complications and risk of death.

Drug Dependence

Drug dependence refers to factors that make it difficult for a person to stop taking a drug. These factors include craving and withdrawal. Drug dependence may be psychologic or physical.

Psychologic dependence refers to a compelling desire to repeat the experience of taking a mind-altering drug (craving) or to avoid the discontent of not using the drug (withdrawal). Desiring the drug experience may be the only obvious reason for compulsive use. Drugs that cause psychologic dependence often produce one or more of the following:

  • Reduced anxiety and tension

  • Elation, euphoria, or other pleasurable mood changes

  • Feelings of increased mental and physical ability

  • Feeling a temporary escape from reality

  • Altered perceptions of the environment (for example, auditory or visual hallucinations)

The intense desire and compulsion to use a drug lead to using it in larger amounts, more frequently, or over a longer period than at first intended. People who are psychologically dependent on a drug give up social and other activities because of drug use. They also continue to use the drug even though they know that the drug is physically harmful or interferes with other aspects of their life, including family and work.

Physical dependence means that stopping the drug results in unpleasant, sometimes painful physical symptoms (withdrawal). Symptoms occur because the body adapts to the continuous presence of a drug.

People going through withdrawal feel sick and may have various unpleasant symptoms depending on the drug involved. Withdrawal from some drugs (such as alcohol or barbiturates) can be serious and even life threatening.

How drug dependence develops is complex and unclear. It depends on interaction of the following:

  • Drug: Drugs vary in how likely they are to make people dependent on them.

  • User: The user’s personality, health, physical characteristics (including genetic makeup), and emotional circumstances affect whether the user is likely to become dependent. For example, the presence of constant pain may drive a person to use drugs inappropriately, as may emotional distress. However, research has not identified any clear-cut biochemical or physical differences in people to explain why some become dependent and others do not.

  • Cultural and social factors: Peer or group pressure and stress (for example, due to work or family obligations) may contribute to dependency, as may the mass media’s portrayal of prescription drugs as safely relieving all distress.

Drug Abuse

Drug abuse can be defined in terms of society’s disapproval and the effect the drug has on the person’s social and emotional well-being. Drug abuse may involve the following:

  • Using drugs, usually illegal drugs, recreationally (not for medical reasons)

  • Using mind-altering drugs to relieve medical problems or symptoms without a health care practitioner’s recommendation

  • Using drugs because of a strong psychologic or physical compulsion (dependence) to use them

Use of illegal drugs is often considered abuse largely because the drugs are illegal. But drugs that are abused are not necessarily illegal, and they may or may not alter the mind. They include prescription drugs, alcohol, and substances in products not considered drugs (such as glue or paint), as well as illegal drugs. People of all socioeconomic groups abuse drugs.

Some people who abuse drugs use an amount large enough or over a period long enough to threaten their quality of life, health, or safety or those of other people. But many people control their abuse of drugs so that it does not adversely affect their health or functioning, making the effects less obvious. Drug abuse does not necessarily include dependence.

Recreational Drug Use

The recreational use of drugs involves using drugs occasionally in relatively small doses and thus often without harm to users. That is, users do not develop tolerance or become physically dependent, and the drug does not physically harm them (at least in the short term). Drugs usually considered recreational include opium, alcohol, nicotine , marijuana, caffeine, hallucinogenic mushrooms, and cocaine.

Recreational drugs are usually taken by mouth or inhaled.

Drug Addiction

Drug addiction has no universally accepted definition. It is characterized by an intense craving for the drug and compulsive, uncontrolled use of the drug despite harm done to the user or other people. People who are addicted spend more and more time obtaining the drug, using the drug, or recovering from its effects. Thus, addiction usually interferes with the ability to work, study, or interact normally with family and friends. Because there is a risk of harm, addiction implies the need to stop drug use, regardless of whether the addict understands and agrees.

Addiction can involve illegal or legal drugs. However, obtaining and using an illegal drug is very different from obtaining and using a legal drug, which may involve simply going to the doctor, getting a prescription, and going to the pharmacy. Obtaining an illegal drug (or a legal drug used without medical need) may involve lying and stealing. For example, people may falsify symptoms to a doctor and visit several doctors with the same symptoms to obtain several prescriptions. When people with severe pain due to advanced cancer become dependent (psychologically and physically) on an opioid such as morphine, their ongoing need for that drug is not usually considered an addiction. However, when people become dependent on heroin, steal to get money to buy heroin, and lie to family members and friends, their 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. They are considered codependents when their own needs are intertwined with perpetuating the addict’s use of the addictive substance. Enablers may call in sick for an addict or make excuses for the addict’s behavior. Enablers may plead with the addict to stop using drugs or alcohol but rarely do anything else to help the addict stop.

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 Birth Defects). Soon after delivery, the newborn can experience severe or even fatal withdrawal, particularly when the doctor is unaware of the mother’s addiction.

Methods of Use

Drugs may be swallowed, smoked, inhaled through the nose as a powder (snorted), or injected. When drugs are injected, their effects may occur more quickly, be stronger, or both.

Drugs may be injected into a vein (intravenously), a muscle (intramuscularly), or under the skin (subcutaneously). Veins in the arms are typically used for intravenous injections, but if these areas become too scarred, drugs may be injected into veins anywhere in the body, including those of the thigh, neck, or armpit.

Complications From Drug Injection

Injecting drugs has more risks than other methods. People are exposed not only to the side effects of the drug but also to problems related to injection itself, such as the following:

  • Adulterants: Adulterants are substances that are added to a drug to alter its physical qualities. They are usually added, without the user’s knowledge, to reduce costs or to make the drug easier to use. Thus, users do not know what they are injecting. In street drugs such as heroin and cocaine, adulterants may also be added to enhance mind-altering properties or to substitute for the drug. Quinine, a common heroin adulterant, can cause double vision, paralysis, and other symptoms of nerve injury, including Guillain-Barré syndrome ( Guillain-Barré Syndrome).

  • Fillers: Some people crush tablets of prescription drugs, dissolve them, and inject the solution intravenously. These people are injecting the fillers that tablets commonly contain (such as cellulose, talc, and cornstarch). Fillers can become trapped in the lungs, causing inflammation. Fillers can also damage heart valves, increasing the risk of infection there (endocarditis).

  • Bacteria and viruses: Injecting drugs with unsterilized needles, particularly needles used by someone else, can introduce bacteria and viruses into the body. As a result, abscesses may develop near the injection site, or bacteria or viruses may travel through the bloodstream to other parts of the body, such as the lungs, heart, brain, or bones, and cause infection. Infection of the heart valves (endocarditis—see see Infective Endocarditis) is a common serious consequence of injecting drugs contaminated with bacteria or using dirty needles. Sharing needles can spread serious infections, such as hepatitis B and C and human immunodeficiency virus (HIV) infection.

  • Injuries due to needle use: Drug abuser’s elbow (myositis ossificans) is caused by repeated, inept needle punctures. The muscle around the elbow is replaced with scar tissue. Subcutaneous injections (those given under the skin, also called skin popping) can cause skin sores. Intravenous injections lead to scarring of veins (tracks), which makes the veins more and more difficult to inject and impairs blood flow.


Screening involves checking for drug abuse in people who do not necessarily have any symptoms of drug abuse. It may be done systematically or randomly in people such as the following:

  • Certain groups of people, such as students, athletes, and prisoners

  • People who are applying for or who already hold certain types of jobs (such as pilots or commercial truck drivers)

  • People who have been involved in motor vehicle or boating accidents or accidents at work

  • People who have attempted suicide by unclear means

  • People in a court-ordered treatment program for drug abuse or with terms of probation or parole requiring abstinence—to monitor compliance

  • People in a substance abuse treatment program—to detect continuing substance abuse and thus better plan treatment

Typically, people have to give consent for screening except in certain circumstances, such as car accidents. Screening cannot determine how often a substance is used and thus cannot distinguish casual users from those with more serious problems. Also, drug screening targets only some substances and thus misses many others. Substances most commonly targeted include alcohol, marijuana, cocaine, opioids, amphetamines, phencyclidine, benzodiazepines, and barbiturates.

A sample of urine, blood, breath, saliva, sweat, or hair may be tested. Urine testing is most common because it is noninvasive, quick, inexpensive, and able to detect many drugs. It can detect drugs that were used within 1 to 4 days, sometimes longer, depending on the drug used. Hair testing is not as widely available but can detect some drugs if they were used in the previous 100 days. Health care practitioners may directly observe the collection of the sample and seal it so that they can be sure the sample has not been tampered with.


Sometimes drug abuse is diagnosed when people go to a health care practitioner because they want help stopping use of the drug. Other people try to hide their drug use.

Practitioners may suspect problems with drug use when they notice changes in mood or behavior in a person. They may then do a thorough physical examination. Signs of drug abuse may be apparent. For example, repeatedly injecting drugs intravenously produces track marks. Track marks are lines of tiny, dark dots (needle punctures) surrounded by an area of darkened or discolored skin. Injecting drugs under the skin causes circular scars or ulcers. Addicts may claim other reasons for the marks, such as frequent blood donations, bug bites, or other injuries.

Health care practitioners also use other methods (such as questionnaires) to identify abuse of some drugs and other substances and to determine the extent of abuse and its effects. Urine and sometimes blood tests may be done to check for the presence of drugs.

If a drug use problem is identified, especially if the drugs are injected, people are thoroughly evaluated for hepatitis, HIV infection, and other infections common in people who use these drugs.


Specific treatment depends on the drug being used, but it typically involves counseling and sometimes involves use of other drugs. Family support and support groups help people remain committed to stopping use of the drug.

Treatment of complications is the same as that for similar complications with other causes. For example, abscesses may be drained, and antibiotics may be used to treat infections.

Because sharing needles is a common cause of HIV infection, a harm-reduction movement was started. Its purpose is to reduce the harm of drug use in users who cannot stop. Thus, users are provided clean needles and syringes so they do not reuse other abusers’ needles. This strategy helps reduce the spread (and the cost to society) of HIV infection and hepatitis.

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