MSD Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Substance Use Disorders


Mashal Khan

, MD, Weill Cornell Medicine

Last full review/revision Dec 2020| Content last modified Dec 2020
Click here for the Professional Version

Substance use disorders generally involve behavior patterns in which people continue to use a substance despite having problems caused by its use.

The substances involved tend to be members of the 10 classes of drug that typically cause substance-related disorders:

These substances all directly activate the brain's reward system and produce feelings of pleasure. The activation may be so strong that people intensely crave the substance. They may neglect normal activities to obtain and use the drug.

Substance use disorders can develop whether or not a drug is legal, is socially acceptable, or has an accepted medical use (with or without a prescription). Details about specific drugs and their effects are discussed elsewhere in THE MANUAL.

The terms "addiction," "abuse," and "dependence" have traditionally been used in regard to people with substance use disorders. However, those terms are all too loosely and variably defined to be very useful and also are often used judgmentally. Thus, doctors now prefer to use the more comprehensive and less negative term "substance use disorder."

Recreational and illicit substance use

Use of illegal drugs, although problematic from a legal standpoint, does not always involve a substance use disorder. On the other hand, legal substances, such as alcohol and prescription drugs (and marijuana in an increasing number of states in the United States), may be involved in a substance use disorder. Problems caused by use of prescription and illegal drugs cut across all socioeconomic groups.

Recreational drug use has existed in one form or another for centuries. People have used drugs for a variety of reasons, including

  • To alter or enhance mood

  • As part of religious ceremonies

  • To gain spiritual enlightenment

  • To enhance performance

People who take drugs recreationally may take them occasionally in relatively small doses, often without doing themselves harm. That is, users do not develop drug withdrawal, 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 (see also Mushroom [Toadstool] Poisoning), and cocaine. Many recreational drugs are considered "natural" because they are close to their plant origin. They contain a mixture of low-concentration psychoactive ingredients rather than an isolated, more concentrated psychoactive compound.

Recreational drugs are usually taken by mouth or inhaled.

Causes of Substance Use Disorders

People usually progress from experimentation to occasional use and then to heavy use and sometimes to a substance use disorder. This progression is complex and only partially understood. The process depends on interactions between the drug, user, and setting.


Drugs in the 10 classes vary in how likely they are to cause a substance use disorder. The likelihood is termed addiction liability. Addiction liability depends upon a combination of factors including

  • How the drug is used

  • How strongly the drug stimulates the brain's reward pathway

  • How quickly the drug works

  • The drug's ability to induce tolerance and/or symptoms of withdrawal

In addition, substances that are legally and/or readily available, such as alcohol and tobacco, are more likely to be used first. As people continue to use a substance, they often see less risk in using it and may begin to increase their use and/or experiment with other substances. People's perception of risk also may be influenced by the social and legal consequences of use.

During treatment of medical illness or following surgical or dental procedures, people are routinely prescribed opioids. If people do not take the whole amount prescribed, the drugs sometimes end up in the hands of people who wish to use them recreationally. Because the use of these drugs for nonmedical purposes has become such a large problem, many health care providers have responded by

  • Prescribing lower amounts of opioid drugs

  • Encouraging people to safely store or dispose of any leftover drugs

  • Expanding prescription take-back programs


Factors in users that may predispose to a substance use disorder include

  • Physical characteristics

  • Personal characteristics

  • Circumstances and disorders

Physical characteristics likely include genetic factors, although researchers have yet to find more than a few biochemical and/or metabolic differences between people who develop a substance use disorder and those who do not.

People with low levels of self-control (impulsivity) or high levels of risk-taking and novelty-seeking behaviors may have an increased risk of developing a substance use disorder. However, there is little scientific evidence to support the concept of the "addictive personality" that has been described by some behavioral scientists.

A number of circumstances and coexisting disorders appear to increase the risk of a substance use disorder. For example,

  • People who are sad, emotionally distressed, or socially alienated may find temporary relief from drug use, which can lead to increased use and sometimes to a substance use disorder.

  • People with other, unrelated mental disorders such as anxiety or depression are at increased risk of developing a substance use disorder. (Doctors use the term "dual diagnosis" to refer to people who have both a mental disorder and a substance use disorder.)

  • People with chronic pain often require opioid drugs for relief. Some of these people later develop a substance use disorder.

However, in many of these people, nonopioid drugs and other treatments do not adequately relieve pain and suffering.


Cultural and social factors are very important in initiating and maintaining (or relapsing to) substance use. Watching family members (eg, parents, older siblings) and peers using substances increases the risk that people will begin using substances. Peers are a particularly powerful influence among adolescents (see Substance Use and Abuse in Adolescents). People who are trying to stop using a substance find it much more difficult if they are around others who also use that substance.

Doctors may inadvertently contribute to harmful use of psychoactive drugs by overzealously prescribing them to relieve stress. Many social factors, including mass media, contribute to the expectation that drugs should be used to relieve all distress.

Diagnosis of Substance Use Disorders

  • A doctor's evaluation

  • Sometimes a person's self-report

Sometimes a substance use disorder is diagnosed when people go to a health care practitioner because they want help stopping use of a drug. Other people try to hide their drug use, and doctors may suspect problems with drug use only when they notice changes in a person's mood or behavior. Sometimes doctors discover signs of substance use during a physical examination. For example, they may discover track marks caused by repeatedly injecting drugs intravenously. 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. People 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 a substance use disorder. Urine and sometimes blood tests may be done to check for the presence of drugs.

Criteria for diagnosis

The criteria for diagnosing a substance use disorder fall into four categories:

  • The person cannot control use of the substance.

  • The person's ability to meet social obligations is compromised by use of the substance.

  • The person uses the substance in physically dangerous situations.

  • The person shows physical signs of use and/or dependence.

Inability to control use

  • The person takes the substance in larger amounts or for a longer time than originally planned.

  • The person desires to stop or cut down use of the substance.

  • The person spends a lot of time obtaining, using, or recovering from the effects of the substance.

  • The person craves the substance.

Social impairment

  • The person fails to fulfill major role obligations at work, school, or home.

  • The person continues to use the substance even though it causes (or worsens) social or interpersonal problems.

  • The person gives up or reduces important social, occupational, or recreational activity because of substance use.

Risky use

  • The person uses the substance in physically hazardous situations (eg, when driving or in dangerous social circumstances).

  • The person continues to use the substance despite knowing it is worsening a medical or psychologic problem.

Physical symptoms*

  • Tolerance: The person needs to use increasingly more of the substance to feel the desired effect.

  • Withdrawal: Unpleasant physical effects occur when the substance is stopped or when it is counteracted by another substance.

* Note that some drugs, particularly opioids, sedative/hypnotics, and stimulants, can result in tolerance and/or withdrawal symptoms even when taken as prescribed for legitimate medical reasons and for relatively brief periods (less than 1 week for opioids). Withdrawal symptoms that develop following appropriate medical use do not warrant the diagnosis of a substance use disorder. For example, when people with severe pain due to advanced cancer become dependent (psychologically and physically) on an opioid such as morphine, their withdrawal symptoms are not considered evidence of a substance use disorder.

People who have 2 or more of these criteria within a 12-month period are considered to have a substance use disorder. The severity of the substance use disorder is determined by the number of criteria met:

  • Mild: 2 to 3 criteria

  • Moderate: 4 to 5 criteria

  • Severe: 6 criteria

Treatment of Substance Use Disorders

  • Varies depending on substance and circumstances

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.

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 others’ needles. This strategy helps reduce the spread (and the cost to society) of HIV infection and hepatitis.

More Information

The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

  • Al-Anon Family Groups: Support services for adults who abuse alcohol, adults who grew up with an alcoholic, and teens affected by someone else's problematic use of alcohol.

  • Alcoholics Anonymous: International fellowship of people with a drinking problem that pioneered the 12-step approach to help its members overcome their addiction to alcohol and help others to do the same. 

  • Dual Access to resources for people with mental illness and problems with substance abuse, including a list of treatment facilities that offer integrated care, information on research, and publications.

  • Hazelden Betty Ford Foundation: Nonprofit treatment provider for alcohol and drug addiction with information on treatment options, recovery advocacy programs, and educational opportunities in addiction counseling.

  • LifeRing: Support for people with drug and alcohol use problems by facilitating sharing of practical experiences and sobriety support as an alternative to traditional 12-step programs.

  • National Alliance on Mental Illness (NAMI): A national mental health organization that provides advocacy, education, support, and public awareness programs and services.

  • Narcotics Anonymous World Services: Helps people combat addiction, regardless of the substance that caused it, through a 12-step program similar to that used by Alcoholics Anonymous.

  • National Institute on Drug Abuse (NIDA): Federal agency that supports scientific research into drug use and its consequences and supplies information about commonly used drugs, research priorities and progress, clinical resources, and grant and funding opportunities. 

  • Substance Abuse and Mental Health Services Administration (SAMHSA): US Department of Health agency that leads public health efforts to improve behavioral health and provides resources, including treatment locators, toll-free helplines, practitioner training tools, statistics, and publications on a variety of substance-related topics.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Test your knowledge

Panic Attacks and Panic Disorder
A panic attack is a brief period of extreme distress, anxiety, or fear that begins suddenly and is accompanied by physical and/or emotional symptoms. Panic attacks are experienced by at least which percentage of American adults during any given year? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID