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A substance use disorder (SUD), also known as a drug use disorder, is a medical condition in which the use of one or more substances leads to a clinically significant impairment or distress.[1] Substance use disorders are characterized by an array of mental, physical, and behavioral symptoms that may cause problems related to loss of control, strain to one's interpersonal life, hazardous use, tolerance, and withdrawal.[2] Drug classes that are involved in SUD include alcohol, phencyclidine, inhalants, stimulants, cannabis, "other hallucinogens", opioids, tobacco, and sedatives, hypnotics, and anxiolytics.[2][3]

Substance use disorder
Other namesDrug use disorder
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Drug addiction and drug dependence are distinct components of substance use disorders. The severity of substance use disorders can vary widely; in the diagnosis of a SUD, the severity of an individual's SUD is qualified as mild, moderate, or severe on the basis of how many of the 11 diagnostic criteria are met. In the DSM-5, the term drug addiction is synonymous with severe substance use disorder.[4][5]

Worldwide 275 million people were estimated to have used an illicit drug in 2016.[6] Of these, 27 million have high-risk drug use otherwise known as recurrent drug use causing harm to their health, psychological problems, or social problems or puts them at risk of those dangers.[7][8] In 2015 substance use disorders resulted in 307,400 deaths, up from 165,000 deaths in 1990.[9][10] Of these, the highest numbers are from alcohol use disorders at 137,500, opioid use disorders at 122,100 deaths, amphetamine use disorders at 12,200 deaths, and cocaine use disorders at 11,100.[9] The number of deaths directly caused by drug use has increased over 60 percent from 2000 to 2015.[11]


Addiction and dependence glossary[12][13][14][4]
  • addiction – a brain disorder characterized by compulsive engagement in rewarding stimuli despite adverse consequences
  • addictive behavior – a behavior that is both rewarding and reinforcing
  • addictive drug – a drug that is both rewarding and reinforcing
  • dependence – an adaptive state associated with a withdrawal syndrome upon cessation of repeated exposure to a stimulus (e.g., drug intake)
  • drug sensitization or reverse tolerance – the escalating effect of a drug resulting from repeated administration at a given dose
  • drug withdrawal – symptoms that occur upon cessation of repeated drug use
  • physical dependence – dependence that involves persistent physical–somatic withdrawal symptoms (e.g., fatigue and delirium tremens)
  • psychological dependence – dependence that involves emotional–motivational withdrawal symptoms (e.g., dysphoria and anhedonia)
  • reinforcing stimuli – stimuli that increase the probability of repeating behaviors paired with them
  • rewarding stimuli – stimuli that the brain interprets as intrinsically positive and desirable or as something to approach
  • sensitization – an amplified response to a stimulus resulting from repeated exposure to it
  • substance use disorder – a condition in which the use of substances leads to clinically and functionally significant impairment or distress
  • tolerance – the diminishing effect of a drug resulting from repeated administration at a given dose

Substance abuse may lead to addiction, substance dependence, or both, depending upon the substance. Medically, physiologic dependence requires the development of tolerance leading to withdrawal symptoms. Both abuse and dependence are distinct from addiction which involves a compulsion to continue using the substance despite the negative consequences, and may or may not involve chemical dependency. Dependence often implies abuse, but abuse frequently occurs without dependence, particularly when an individual first begins to abuse a substance. Dependence involves physiological processes while substance abuse reflects a complex interaction between the individual, the abused substance and society.[15]

Substance abuse is sometimes used as a synonym for drug abuse, drug addiction, and chemical dependency, but actually refers to the use of substances in a manner outside sociocultural conventions. All use of controlled drugs and all use of other drugs in a manner not dictated by convention (e.g. according to physician's orders or societal norms) is abuse according to this definition; however there is no universally accepted definition of substance abuse.

Substance use may be better understood as occurring on a spectrum from beneficial to problematic use. This conceptualization moves away from the ill-defined binary antonyms of "use" vs. "abuse" towards a more nuanced, public health-based understanding of substance use.

Signs and symptomsEdit

The DSM definition of addiction can be boiled down to compulsive use of a substance (or engagement in an activity) despite ongoing negative consequences. The medical community makes a distinction between physical dependence (characterized by symptoms of physical withdrawal symptoms, like tremors and sweating) and psychological dependence (emotional-motivational withdrawal symptoms)[citation needed]. Physical dependence is simply needing a substance to function. Humans are all physically dependent upon oxygen, food and water. A drug can cause physical dependence and not psychological dependence (for example, some blood pressure medications, which can produce fatal withdrawal symptoms if not tapered) and some can cause psychological dependence without physical dependence (the withdrawal symptoms associated with cocaine are all psychological, there is no associated vomiting or diarrhea as there is with opiate withdrawal).


There are many known risk factors associated with an increased chance of developing a substance use disorder. Children born to parents with SUDs have roughly a two-fold increased risk in developing a SUD compared to children born to parents without any SUDs.[16] Taking highly addictive drugs, and those who develop SUDs in their teens are more likely to have continued symptoms into adulthood.[16] Other common risk factors are being male, being under 25, having other mental health problems, and lack of familial support and supervision.[16] Psychological risk factors include high impulsivity, sensation seeking, neuroticism and openness to experience in combination with low conscientiousness.[17][18]


Individuals whose drug or alcohol use cause significant impairment or distress may have a substance use disorder (SUD).[2] Diagnosis usually involves an in-depth examination, typically by psychiatrist, psychologist, or drug and alcohol counselor.[19] The most commonly used guidelines are published in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).[19] There are 11 diagnostic criteria which can be broadly categorized into issues arising from substance use related to loss of control, strain to one's interpersonal life, hazardous use, and pharmacologic effects.[2]

DSM-5 guidelines for the diagnosis of a substance use disorder requires that the individual have significant impairment or distress from their pattern of drug use, and at least two of the symptoms listed below in a given year.[2]

  1. Using more of a substance than planned, or using a substance for a longer interval than desired
  2. Inability to cut down despite desire to do so
  3. Spending substantial amount of the day obtaining, using, or recovering from substance use
  4. Cravings or intense urges to use
  5. Repeated usage causes or contributes to an inability to meet important social, or professional obligations
  6. Persistent usage despite user's knowledge that it is causing frequent problems at work, school, or home
  7. Giving up or cutting back on important social, professional, or leisure activities because of use
  8. Using in physically hazardous situations, or usage causing physical or mental harm
  9. Persistent use despite the user's awareness that the substance is causing or at least worsening a physical or mental problem
  10. Tolerance: needing to use increasing amounts of a substance to obtain its desired effects
  11. Withdrawal: characteristic group of physical effects or symptoms that emerge as amount of substance in the body decreases

There are additional qualifiers and exceptions outlined in the DSM. For instance, if an individual is taking opiates as prescribed, they may experience physiologic effects of tolerance and withdrawal, but this would not cause an individual to meet criteria for a SUD without additional symptoms also being present.[2] A medical professional trained to evaluate and treat substance use disorders will take these nuances into account during a diagnostic evaluation.


Substance use disorders range can range widely in severity, and there are numerous methods to monitor and qualify the severity of an individual's SUD. The DSM-5 includes specifiers for severity of a SUD.[2] Individuals who meet only 2 or 3 criteria are often deemed to have mild SUD.[2] Substance users who meet 4 or 5 criteria may have their SUD described as moderate, and persons meeting 6 or more criteria as severe.[2] In the DSM-5, the term drug addiction is synonymous with severe substance use disorder.[4][5] The quantity of criteria met offer a rough gauge on the severity of illness, but licensed professionals will also take into account a more holistic view when assessing severity which includes specific consequences and behavioral patterns related to an individual's substance use.[2] They will also typically follow frequency of use over time, and assess for substance-specific consequences, such as the occurrence of blackouts, or arrests for driving under the influence of alcohol, when evaluating someone for an alcohol use disorder.[2] There are additional qualifiers for stages of remission that are based on the amount of time an individual with a diagnosis of a SUD has not met any of the 11 criteria except craving.[2] Some medical systems refer to an Addiction Severity Index to assess the severity of problems related to substance use.[20] The index assesses potential problems in seven categories: medical, employment/support, alcohol, other drug use, legal, family/social, and psychiatric.[21]

Screening testsEdit

There are several different screening tools that have been validated for use with adolescents such as the CRAFFT and adults such as CAGE.




Depending on the severity of use, and the given substance, early treatment of acute withdrawal may include medical detoxification. Of note, acute withdrawal from heavy alcohol use should be done under medical supervision to prevent a potentially deadly withdrawal syndrome known as delirium tremens. See also Alcohol detoxification.


Therapists often classify people with chemical dependencies as either interested or not interested in changing. About 11% of Americans with substance use disorder seek treatment, and 40–60% of those people relapse within a year.[22] Treatments usually involve planning for specific ways to avoid the addictive stimulus, and therapeutic interventions intended to help a client learn healthier ways to find satisfaction. Clinical leaders in recent years have attempted to tailor intervention approaches to specific influences that affect addictive behavior, using therapeutic interviews in an effort to discover factors that led a person to embrace unhealthy, addictive sources of pleasure or relief from pain.

Behavioral pattern Intervention Goals
Low self-esteem, anxiety, verbal hostility Relationship therapy, client centered approach Increase self-esteem, reduce hostility and anxiety
Defective personal constructs, ignorance of interpersonal means Cognitive restructuring including directive and group therapies Insight
Focal anxiety such as fear of crowds Desensitization Change response to same cue
Undesirable behaviors, lacking appropriate behaviors Aversive conditioning, operant conditioning, counter conditioning Eliminate or replace behavior
Lack of information Provide information Have client act on information
Difficult social circumstances Organizational intervention, environmental manipulation, family counseling Remove cause of social difficulty
Poor social performance, rigid interpersonal behavior Sensitivity training, communication training, group therapy Increase interpersonal repertoire, desensitization to group functioning
Grossly bizarre behavior Medical referral Protect from society, prepare for further treatment
Adapted from: Essentials of Clinical Dependency Counseling, Aspen Publishers

From the applied behavior analysis literature and the behavioral psychology literature, several evidence-based intervention programs have emerged, such as behavioral marital therapy, community reinforcement approach, cue exposure therapy, and contingency management strategies.[23][24] In addition, the same author suggests that social skills training adjunctive to inpatient treatment of alcohol dependence is probably efficacious.


The disability-adjusted life year, a measure of overall disease burden (number of years lost due to ill-health, disability or early death), from drug use disorders per 100,000 inhabitants in 2004
  no data

Rates of substance use disorders vary by nation and by substance, but the overall prevalence is high.[25] On a global level, men are affected at a much higher rate than women.[25] Younger individuals are also more likely to be affected than older adults.[25]

United StatesEdit

In 2017, roughly 7% of Americans aged 12 or older had a SUD in the past year.[26] Rates of alcohol use disorder in the past year was just over 5%. Approximately 3% of people aged 12 or older had an illicit drug use disorder.[26] The highest rates of illicit drug use disorder was among those aged 18 to 25 years old, at roughly 7%.[26][25]

There were over 72,000 deaths from drug overdose in the United States in 2017.[27] This represents a 3-fold increase in mortality from overdose from 2002 to 2017.[27] Overdose fatalities from synthetic opioids, which typically involve fentanyl, have risen sharply in the past several years to contribute to nearly 30,000 deaths per year.[27] Death rates from synthetic opioids like fentanyl have increased 22-fold in the period from 2002 to 2017.[27] Heroin and other natural and semi-synthetic opioids combined to contribute to roughly 31,000 overdose fatalities.[27] Cocaine contributed to roughly 15,000 overdose deaths, while methamphetamine and benzodiazepines each contributed to roughly 11,000 deaths.[27] Of note, the mortality from each individual drug listed above cannot be summed because many of these deaths involved combinations of drugs, such as overdosing on a combination of cocaine and an opioid.[27]

Deaths from alcohol consumption account for the loss of over 88,000 lives per year.[28] Tobacco remains the leading cause of preventable death, responsible for greater than 480,000 deaths in the United States each year.[29]


  1. ^ "NAMI Comments on the APA's Dr aft Revision of the DSM-V Substance Use Disorders" (PDF). National Alliance on Mental Illness. Archived from the original (PDF) on 22 January 2015. Retrieved 2 November 2013.
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    Addiction: A term used to indicate the most severe, chronic stage of substance-use disorder, in which there is a substantial loss of self-control, as indicated by compulsive drug taking despite the desire to stop taking the drug. In the DSM-5, the term addiction is synonymous with the classification of severe substance-use disorder.
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