• Clinical science

Substance-related and addictive disorders


Substance-related disorders are a class of psychiatric disorders characterized by a craving for, the development of a tolerance to, and difficulties in controlling the use of a particular substance or a set of substances, as well as withdrawal syndromes upon abrupt cessation of substance use. While these substances may have different mechanisms of action, their addictive potential typically lies in the way they act on the brain's reward system and affect emotion, mood, and perception – producing what is colloquially referred to as a “high.” Individuals with a substance use disorder will frequently harm themselves and/or others as a result of substance use. Patients with substance use disorders often present with other psychiatric conditions that also require treatment, such as bipolar disorder, major depressive disorder, or anxiety disorder. Generally, treatment for substance use disorders includes long-term psychotherapy or group therapy in addition to medical supervision of withdrawal symptoms.

In gambling disorder, individuals feel a compulsion to gamble despite negative consequences and/or multiple attempts to stop. Gambling disorder is thought to involve many of the same neurobiological mechanisms as substance-related addictions and shares some of the same psychosocial risk factors.


Substance use disorder

  • Definition: pathologic collection of cognitive, behavioral, and physiological symptoms related to the use of a substance
  • Epidemiology
    • Sex: >
    • Alcohol and nicotine use is most common
  • Criteria
    1. Impaired control
      • Using substance inlarger amounts and/or for a longer time than originally intended
      • Repeated failed attempts to cut down on use
      • Spending a great deal of time on substance-related activities (e.g., buying, using, recovering from use, etc.)
      • Intense desire to obtain and use substance (craving)
    2. Social impairment
      • Problems fulfilling work, school, family, or social obligations (e.g., not attending work or school, neglecting children or partner, etc.)
      • Problems with interpersonal relationships directly related to substance use
      • Reduced social and recreational activities (e.g., less time socializing with friends, spending less time with family)
    3. Risky use
      • Use in physically hazardous situations (e.g., operating heavy machinery, driving a car)
      • Use despite awareness of physical problems (e.g., continued alcohol use despite having cirrhosis)
    4. Pharmacologic indicators
      • Drug tolerance
        • Definition: the need for individuals to continuously increase the dose of a substance to achieve the same desired effect
        • Corollary: individuals experience less of an effect despite taking the same amount of a substance
        • The degree of tolerance can vary greatly depending on factors such as route of administration, duration of use, and genetic factors!
      • Drug withdrawal

Withdrawal from some substances such as alcohol, benzodiazepines, and barbiturates can be fatal!

Differential diagnosis

Differential diagnosis of drug intoxication
Pupils Blood pressure Pulse Other symptoms
Opioids Miosis Hypotension Bradycardia
  • Respiratory depression
  • Absent proprioceptive reflexes
Cannabinoids Mydriasis Hypertension/hypotension Tachycardia
Cocaine Mydriasis Hypertension Tachycardia
Amphetamines Mydriasis Hypertension Tachycardia
Hallucinogens Mydriasis Hypertension Tachycardia
Gamma-hydroxybutyric acid

Variable pupillary reaction (miotic or mydriatic)

Hypotension Bradycardia


Alcohol use disorder

See alcohol use disorder.

Caffeine use disorder

  • Substance: caffeine (usually ingested with coffee or tea)
  • Action: adenosine antagonist → increased cAMPneurological excitation
  • Epidemiology: most prevalent psychoactive substance in the US
    • Overdose
    • Withdrawal: headache, irritability, drowsiness, muscle pain, depression
  • Treatment
    • Overdose: supportive
    • Withdrawal: resolves spontaneously within ∼ 10 days


Cannabis-related disorders

Medical marijuana can be used to increase appetite and treat nausea/vomiting in terminally ill patients, relieve pain in cancer patients, and reduce intraocular pressure in patients with glaucoma.

DroNABINOl is a pharmaceutical canNABINOid.


Phencyclidine use disorder


Hallucinogen use disorder


Inhalant use disorder


Opioid use disorder

Overdose with opioid analgesics is the most common cause of death among adults < 50 years.


Sedative, hypnotic, and anxiolytic use disorder

See sections on benzodiazepine dependence and barbiturate overdose in the sedative-hypnotic drugs article.

Cocaine use disorder

β-blockers are contraindicated because they can cause unopposed α-agonism, which worsens vasospasm!

Suspect cocaine use in individuals presenting with weight loss, behavioral changes, and erythema of the turbinates and nasal septum!


Amphetamine use disorder


Synthetic cathinones

Nicotine use disorder


Gambling disorder

  • Definition: : addictive disorder in which individuals feel a compulsion to gamble despite negative consequences and/or multiple attempts to stop.
  • Epidemiology
    • Sex: >
    • No specific age group
  • Etiology: combination of factors (genetic, environmental, neurochemical abnormalities)
  • Diagnosis: ≥ 4 of the following in a 12 month period
    • Relying on others for financial support to support habit
    • Restlessness when attempting to stop gambling
    • Constant preoccupation with gambling
    • Continuous gambling in an attempt to undo losses (“chasing one's losses”)
    • Jeopardizing relationships or careers as a result of gambling
    • Numerous failed attempts to quit gambling
    • Lying to others to conceal the extent of gambling
    • Belief that gambling helps relieve dysphoria
  • Treatment
  • Complications
    • Often occurs in conjunction with other psychiatric disorders (especially anxiety and substance use)
    • Associated with poor general health, including tachycardia and angina


Gamma-hydroxybutyric acid use disorder

Gamma-hydroxybutyric acid is sometimes used as a “date rape” drug because of its quick onset, amnestic effects, and complicated detection!