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Substance Use Disorders


Mashal Khan

, MD, Weill Cornell Medicine

Last full review/revision Nov 2020| Content last modified Nov 2020
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Substance use disorders are a type of substance-related disorder that involve a pathologic pattern of behaviors in which patients continue to use a substance despite experiencing significant problems related to its use. There may also be physiologic manifestations, including changes in brain circuitry.

The substances involved are typically members of the 10 classes of drug that typically cause substance-related disorders. These substances all directly activate the brain reward system and produce feelings of pleasure. The activation may be so intense that patients intensely crave the substance and neglect normal activities to obtain and use it.

The common terms "addiction," "abuse," and "dependence" have often been used with regard to substance use, but these terms are too loosely and variably defined to be very useful in systematic diagnosis. "Substance use disorder" is more comprehensive and has fewer negative connotations.

Recreational and illicit substance use

Use of illegal drugs, although problematic because it is illegal, does not always involve a substance use disorder. Conversely, legal substances, such as alcohol and prescription drugs (and cannabis in an increasing number of US 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, although typically not sanctioned by society, is not a new phenomenon, and has existed in some form or another for centuries. People have used drugs for a variety of reasons:

  • To alter or enhance mood

  • As part of religious ceremonies

  • To obtain spiritual enlightenment

  • To enhance performance

Some users apparently are unharmed; they tend to use drugs episodically in relatively small doses, precluding clinical toxicity and development of tolerance and physical dependence. Many recreational drugs (eg, crude opium, alcohol, marijuana, caffeine, hallucinogenic mushrooms, coca leaf) are “natural” (ie, close to plant origin); they contain a mixture of relatively low concentrations of psychoactive compounds and are not isolated psychoactive compounds.

Etiology of Substance Use Disorders

People with a substance use disorder usually progress from experimentation to occasional use and then to heavy use and sometimes a substance use disorder. This progression is complex and only partially understood. The process depends on interaction 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

  • Route of administration

  • Rate at which the drug crosses the blood-brain barrier and stimulates the reward pathway

  • Time to onset of effect

  • Ability to induce tolerance and/or withdrawal symptoms

In addition, substances that are legally and/or readily available (eg, alcohol, tobacco) are more likely to be used initially and thus increase the risk of progression to problematic use. Further, as perception of the risk in using a particular substance diminishes, there may be subsequent experimentation and/or recreational use of the drug, increasing exposures to substances of abuse. Fluctuations in perception of risk are influenced by multiple factors, including findings regarding medical and psychiatric sequelae of use and social outcomes.

During treatment of medical illness or following surgical or dental procedures, patients are routinely prescribed opioids. A substantial portion of these drugs go unused, representing a significant source for children, adolescents, and adults who wish to use them for nonmedical purposes. In response, there has been increased emphasis on the need to

  • Prescribe opioid drugs in lower amounts more appropriate to the likely duration and severity of pain

  • Promote safe storage of leftover drugs

  • Expand prescription take-back programs


Predisposing factors in users include the following:

  • Physical characteristics

  • Personal characteristics

  • Circumstances and disorders

Physical characteristics likely include genetic factors. However, although researchers have long tried to identify specific factors, they have found few biochemical or metabolic differences between people who do and do not develop substance use disorder.

Personal characteristics are not clearly a strong factor, although people with low levels of self-control (impulsivity) or high levels of risk-taking and novelty-seeking may have an increased risk of developing substance use disorder. However, the concept of the addictive personality that has variously been described by some behavioral scientists has little scientific evidence to back it.

A number of circumstances and coexisting disorders appear to increase risk. For example, people who are sad, emotionally distressed, or socially alienated may find these feelings are temporarily relieved by a drug; this can lead to increased use and sometimes a substance use disorder. Patients with other, unrelated psychiatric disorders are at increased risk of developing a substance use disorder. Patients with chronic pain (eg, back pain, pain due to sickle cell disease, neuropathic pain, fibromyalgia) often take opioid drugs for relief; many subsequently develop a substance use disorder. However, in many of these patients, nonopioid drugs and other treatments can adequately relieve pain and suffering.

Pearls & Pitfalls

  • The concept of the addictive personality that has variously been described by some behavioral scientists has little scientific evidence to back it.


Cultural and social factors are very important in initiating and maintaining (or relapsing to) substance use. Observing family members (eg, parents, older siblings) and peers using substances increases risk that people will begin using substances. Peers are a particularly powerful influence among adolescents (see Drug and Substance 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.

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

Diagnosis of Substance Use Disorders

  • Specific criteria

Diagnosis of substance use disorder is based on identifying a pathologic pattern of behaviors in which patients continue to use a substance despite experiencing significant problems related to its use. The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM 5) gives 11 criteria divided into 4 categories.

Impaired control over 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 substantial time obtaining, using, or recovering from the effects of the substance

  • The person has an intense desire (craving) to use 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

Pharmacologic symptoms*

  • Tolerance: The person needs to progressively increase the drug dose to produce intoxication or the desired effect, or the effect of a given dose decreases over time

  • Withdrawal: Untoward physical effects occur when the drug is stopped or when it is counteracted by a specific antagonist

* 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 (< 1 week for opioids). Withdrawal symptoms that develop following such appropriate medical use do not count as criteria for diagnosis of a substance use disorder.

People who have 2 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 symptoms:

  • Mild: 2 to 3 criteria

  • Moderate: 4 to 5 criteria

  • Severe: 6 criteria

Treatment of Substance Use Disorders

  • Varies depending on substance and circumstances

Treating substance use disorder is challenging and includes one or more of the following:

  • Acute detoxification

  • Prevention and management of withdrawal

  • Cessation (or rarely, reduction) of use

  • Maintenance of abstinence

Different treatment phases may be managed with drugs and/or counseling and support. Specific measures and issues are discussed under the specific substance elsewhere in THE MANUAL, including Alcohol Use Disorders and Opioid Use Disorder.

With increasing evidence and greater understanding of the biologic processes underlying compulsive drug-taking, substance use disorders have become much more firmly established as medical illnesses. As such, these illnesses are amenable to various forms of treatment, including support groups (Alcoholics Anonymous and other Twelve Step programs); psychotherapy (eg, motivational enhancement therapy, cognitive-behavioral therapy, relapse prevention); and medications, ranging from agonist therapy (eg, nicotine replacement therapy for tobacco use disorder, methadone and buprenorphine for opioid use disorder) to novel approaches currently under investigation. Focus on accurate identification of patients with substance use disorders and referral for specialty treatment will help greatly in reducing individual consequences as well as societal impact.

Key Points

  • Substance use disorder involves a pathologic pattern of behaviors in which patients continue to use a substance despite experiencing significant problems related to its use.

  • Manifestations are categorized into impaired control over use, social impairment, risky use, and pharmacologic symptoms.

  • The terms "addiction," "abuse," and "dependence" are vague and value-laden; it is preferable to speak of "substance use disorders" and focus on the specific manifestations and their severity.

  • The consequences and treatment of substance use disorder vary greatly depending on the substance.

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