Substance use disorders: approach and treatment

• A substance use disorder (SUD) is a problematic pattern of use of an intoxicating substance, leading to clinically significant impairment or distress, with at least two of eleven features present over twelve months.
• The same diagnostic framework applies to alcohol, opioids, stimulants, cannabis, sedatives, and other substances; severity is rated mild, moderate, or severe by symptom count.
• Screening is part of routine care: ask about substance use, then use validated tools such as CAGE, AUDIT, or DAST as appropriate.
• Treatment combines psychosocial care with medication where evidence supports it: opioid agonist therapy, nicotine replacement and other cessation aids, and alcohol pharmacotherapy; cannabis and stimulant disorders are managed predominantly behaviourally.
• The approach is stepped and longitudinal: brief intervention, motivational interviewing, risk stratification, medically supervised withdrawal where needed, then maintenance and relapse prevention.

By the end of this page you should be able to:

1. Define a substance use disorder and classify its severity using the current diagnostic framework.
2. Compare intoxication and withdrawal syndromes for the main substances.
3. Interpret common screening scores and state the investigation and referral thresholds they imply.
4. Carry out brief intervention and motivational interviewing in a person who is ambivalent about change.
5. Choose first-line pharmacological treatment for alcohol, opioid, nicotine, and cannabis use disorders, with doses, and know when to refer.
6. Outline the special considerations for pregnancy, young people, and older adults.

The modern framework merges the older categories of "abuse" and "dependence" into a single continuum, because severity matters more than labels. The eleven criteria fall into four groups: impaired control, social impairment, risky use, and pharmacological effects (tolerance and withdrawal).^[1] Severity is: mild when two or three criteria are met, moderate when four or five are met, and severe when six or more are met.^[1]

Tolerance and withdrawal that occur solely as a consequence of medical treatment, as with a patient taking prescribed opioids for pain, do not count as criteria for an SUD.^[1]

Withdrawal is not established for every substance; hallucinogens, phencyclidine, and inhalants have no withdrawal criterion, leaving ten criteria for those disorders.^[1]

SUDs are common worldwide and carry a large burden of illness, disability, and premature death.^[1] They are more common in men than in women for most substances, although the gap narrows with alcohol and is reversed in some medication-related disorders. Age of onset is usually in adolescence or young adulthood.

Risk is shaped by many influences rather than a single cause:

• Biological factors, including genetic vulnerability and developmental stage.
• Adverse childhood experiences, social disadvantage, and trauma.
• Co-occurring mental health conditions such as depression, anxiety, and attention deficit hyperactivity disorder.
• Availability of the substance, social norms, and legal context.
• For injected drugs, infectious risks including blood-borne viruses.

Dependence develops through repeated use interacting with brain systems for reward, executive control, and stress reactivity, so a SUD behaves like a chronic, relapsing medical condition rather than a moral failing.^[1]

Intoxicating substances increase dopamine in the nucleus accumbens, the core of the brain's reward circuitry. With repeated use, neuro-adaptation occurs: tolerance means more drug is needed for the same effect, and withdrawal symptoms appear when levels fall. Over time, reward sensitivity decreases, stress-system activity increases, and executive control weakens, producing the compulsive, cue-driven behaviour that characterises addiction.^[1]

These changes explain why a person may continue using despite serious harm: the brain has learned to value the substance over natural rewards, not because of weak willpower. They also explain why medically supervised withdrawal alone is rarely enough: the neural pathways persist long after the drug has cleared.

Stigma, criminalisation, and lack of access to treatment amplify harm and reduce help-seeking, so patient-centred, non-judgemental care is part of effective treatment.^[1]

Ask directly and routinely about substance use in every clinical encounter; most patients will not volunteer it. Record for each substance: type, route, quantity, frequency, last use, and consequences. Complaints come in many forms:

• Direct requests for help with stopping or cutting down.
• Intoxication or withdrawal symptoms as the presenting illness.
• Complications: overdose, infections, liver disease, chest pain, weight loss.
• Mental health symptoms: low mood, anxiety, psychosis, sleep disturbance.
• Social and legal problems: relationship breakdown, job loss, financial strain.

Many patients meet criteria for more than one SUD, and many have both an SUD and another mental health disorder; both should be identified and treated.^[1]

There is often no specific sign. Look for:

• Evidence of intoxication or withdrawal at the time of the visit (see the table of syndromes below).
• Injection marks, nasal damage, or smoking-related changes.
• Liver disease, peripheral neuropathy, or cognitive impairment.
• Signs of infection, including endocarditis in people who inject drugs.
• Nutritional deficiency and weight loss.

A brief, structured mental state and risk assessment (including suicidal intent) should accompany the physical examination.

SUD is often missed because its presentation is nonspecific. Consider instead, or in addition:

• Alcohol-related cognitive disorders in later life.
• Prescription or over-the-counter drug overuse in an older adult.
• A primary mood, anxiety, or psychotic disorder that drives self-medication.
• Recreational use without impairment (does not meet criteria).
• Substance-induced disorders (intoxication, withdrawal, or substance-induced mental disorder), where symptoms are attributable to recent use and expected to resolve.

The following table helps separate a SUD from related problems; features overlap, so clinical judgement and time are needed.

Diagnosis is clinical, based on the history and the criteria. Investigations support assessment, risk, and treatment rather than proving the diagnosis. Routine care should include:

• Biological testing: urine or oral fluid drug screens, breath or blood alcohol, and laboratory markers of harm such as liver tests; a screen is not the sole method of diagnosis.^[4]
• Severity scores for alcohol withdrawal (for example, CIWA-Ar) where used locally.
• Screening for complications: infection panels, electrocardiogram, chest imaging as indicated.
• Mental health and cognitive assessment, including suicide risk.

The first tests a student should know are screening tools. The following table summarises the tools most used in practice and the actions their scores imply.

Liver enzymes, elevated gamma-glutamyl transferase, and raised mean corpuscular volume support heavy alcohol use but are neither sensitive nor specific. In everyone who uses drugs, offer testing for hepatitis B and C and HIV, and vaccinate where appropriate.^[4]

Use the DSM-5-TR criteria and severity in the definition above. In addition:

• Co-occurring disorders: if symptoms consistent with both an SUD and a mental health disorder are present, assess for both and refer for specialist behavioural healthcare when indicated.^[1]
• Consider the ten substance classes, noting that use of prescribed medication exactly as directed does not count as tolerance or withdrawal.
• Staging of alcohol use: categorise as hazardous (increasing-risk), harmful (higher-risk), or possible dependence using the AUDIT bands, and use the same bands to guide brief advice or referral.^[14]

Management is agreed with the patient, moves step by step, and is reconsidered regularly because people move between stages of readiness to change.

People change through a series of stages: pre-contemplation, contemplation, preparation, action, and maintenance.^[2] They usually move through them in a spiral rather than a straight line, and most need several cycles before change becomes stable.

Motivational interviewing is a counselling style developed for this situation. It focuses on enhancing the patient's own motivation to change, explores ambivalence respectfully, and avoids confrontation. Useful techniques are: reflective listening, exploring the pros and cons of change, supporting self-efficacy, and giving personalised, non-judgemental feedback.^[2] Brief motivational interventions of about ten to forty-five minutes, delivered in two short sessions, can be used opportunistically by non-specialists.^[4]

The Transtheoretical Model and motivational interviewing are a framework for tailoring interventions to the person's current stage rather than a single script.^[2]

• Psychoeducation about the disorder, health risks, and treatment options.
• Cognitive behavioural therapy, motivational enhancement therapy, and their combination with contingency management, especially for cannabis and stimulant disorders.
• Behavioural couples or family therapy where a partner can participate.^[4]
• Self-help and peer support (for example, twelve-step and SMART Recovery groups).
• Structured relapse prevention: identifying triggers, planning coping responses, and reducing cue exposure.
• Contingency management: reinforcing desired behaviours such as abstinence and attendance with timely incentives.^[4]

Psychosocial care is the foundation. Evidence-based options include cognitive behavioural, behavioural, and social network or environment-based therapies; behavioural couples therapy; and contingency management.^[4][5]

Pharmacological help is considered for harmful drinking or mild dependence unresponsive to psychological treatment, and for moderate to severe dependence:

• Acamprosate or oral naltrexone together with a psychological intervention; evidence is stronger for naltrexone than acamprosate in milder presentations.^[5]
• For alcohol dependence, extended-release naltrexone may be given as 380 mg by deep intramuscular gluteal injection every four weeks, after the patient has stopped drinking, as part of a full management programme with counselling.^[11]

Assisted withdrawal ("detoxification") is needed for many dependent drinkers:

• Assess severity with CIWA-Ar (or local protocol), with admission for those at risk of seizures or delirium tremens.^[6]
• The preferred medication is a benzodiazepine, such as chlordiazepoxide or diazepam, on a fixed-dose or symptom-triggered regimen.^[5]
• Delirium tremens: oral lorazepam is first-line, with parenteral lorazepam or haloperidol if needed (often off-label, so check local guidance).^[6]
• Alcohol-withdrawal seizures: a quick-acting benzodiazepine such as lorazepam; do not use phenytoin.^[6]
• Wernicke's encephalopathy: thiamine, parenterally when suspected, followed by oral, then maintenance.^[6]

Severe dependence with limited social support, complex comorbidity, or failed community treatment may require residential or intensive community programmes.^[5]

Opioid agonist (medication for opioid use disorder) greatly reduces illicit opioid use, retains people in treatment, and reduces overdose death when compared with placebo or no medication.^[12] Medication should be considered for every patient with an opioid use disorder, reserved for those with moderate to severe disorder with physical dependence, and offered as part of a plan including counselling and psychosocial support.^[12]

Options:

1. Buprenorphine/naloxone sublingual film: place it when objective signs of moderate opioid withdrawal are present, not less than six hours after the last short-acting opioid. On day 1 give up to 8 mg/2 mg (starting at 2 mg/0.5 mg or 4 mg/1 mg, titrating upwards in 2 mg or 4 mg increments at roughly two-hour intervals); on day 2 up to 16 mg/4 mg; maintenance doses usually fall between 4 mg/1 mg and 24 mg/6 mg daily. For patients dependent on methadone or other long-acting opioids, induction with buprenorphine monotherapy is recommended, then conversion to buprenorphine/naloxone. There is no maximum recommended duration; many patients need treatment indefinitely.^{[10] [9]}
2. Methadone: it may be dispensed only by licensed, federally certified opioid treatment programmes; doses are individualised.^[12]
3. Extended-release naltrexone: 380 mg by deep intramuscular gluteal injection every four weeks, after an opioid-free period of at least seven to ten days, to avoid precipitating withdrawal.^[11]

Buprenorphine/naloxone products are not suitable for patients with severe hepatic impairment and may not be appropriate for moderate impairment.^[10] Avoid abrupt discontinuation; taper when stopping.^[10]

Counselling, contingency management, and behavioural couples therapy are all recommended components.^[4] Harm-reduction measures include safer-injecting advice, naloxone overdose-rescue supply, blood-borne virus testing and vaccination, and access to needle and syringe services.

WHO guidance and comparative reviews consistently support three first-line pharmacological options, plus behavioural support: varenicline, nicotine replacement therapy, and bupropion. Cytisine is also recommended. Combining pharmacotherapy with behavioural intervention increases quitting success.^[8]

• Varenicline: start one to two weeks before the quit date; 500 micrograms daily for three days, then 500 micrograms twice daily for four days, then 1 mg twice daily for eleven weeks; reduce to 500 micrograms twice daily if not tolerated; total duration twelve weeks. Avoid in end-stage renal disease (maximum 1 mg daily in severe impairment). Caution in cardiovascular disease, seizure predisposition, and pregnancy.^[9]
• Nicotine replacement: combination NRT (a long-acting patch plus a short-acting gum, lozenge, or spray) is preferred to single therapy. Patch strength is chosen by daily cigarette count (21, 14, or 7 mg daily), with short-acting forms as needed; total duration eight to twelve weeks, then taper.^{[9] [8]}
• Bupropion sustained-release: start one to two weeks before quitting; 150 mg daily for six days, then 150 mg twice daily (minimum eight hours between doses; daily maximum 300 mg); duration seven to nine weeks. Contraindicated in seizure disorders, CNS tumour, acute alcohol or benzodiazepine withdrawal, eating disorders, severe hepatic cirrhosis, bipolar disorder, and with monoamine oxidase inhibitors.^[9]
• Cytisine: licensed course of twenty-five days (one hundred tablets) in some countries.^[9]

Psychosocial interventions remain first-line: motivational enhancement therapy, cognitive behavioural therapy, and their combination with contingency management have the most consistent support. Family-based therapies are useful in adolescents and young adults.^[13]

No medication has robust evidence for routine use. Trials of dronabinol, nabilone, nabiximols, cannabidiol, gabapentin, topiramate, N-acetylcysteine, and others have shown inconsistent benefit; psychosocial therapies should remain the first-line approach.^[13] Symptoms of intoxication and withdrawal are managed supportively; for severe anxiety or agitation during cannabis withdrawal, short-course benzodiazepines may be used cautiously, with attention to misuse.^[13]

No medication has established first-line benefit for stimulant use disorder. Management relies on contingency management, cognitive behavioural therapy, and motivational enhancement.^[4][13] Screening and biological testing, family support, and treatment of comorbid psychiatric disorders are important. For sedative or benzodiazepine dependence, manage withdrawal with a gradual, planned benzodiazepine taper in a supervised setting; abrupt stopping risks seizures.

Pregnancy: abstinence and safety are the primary goals. Pregnant women with opioid use disorder should be offered opioid agonist treatment (methadone or buprenorphine) with obstetric, addiction, and paediatric liaison; neonatal opioid withdrawal syndrome is an expected, treatable outcome that must be balanced against the risks of untreated addiction.^[10] All women who misuse alcohol should be advised that there is no known safe level in pregnancy. Alcohol-withdrawal medication choices in pregnancy require specialist advice.^[6]

Young people: the same criteria apply, but thresholds for intervention should be lower and family involvement is often helpful. Use developmentally appropriate instruments and family-based therapies where available.

Older adults: prevalence is rising; presentation is often complicated by medication-related misuse, cognitive impairment, and falls. Standard tools may under-perform, so a lower threshold for suspicion and a medication review are prudent.

The WHO mhGAP guideline is designed for non-specialist health workers in low- and middle-income countries and offers a stepped, evidence-based framework for alcohol and drug use disorders within primary care.^[7] Its emphasis on brief interventions, psychosocial care, and harm reduction is realistic where specialists and laboratory testing are scarce. Recommendations should be adapted to local formularies and resources; check your national guideline before applying doses.

Complications depend on substance and route of use, but common ones include:

• Acute overdose and death, especially with opioids, alcohol, or mixed intoxication.
• Withdrawal syndromes, some of which (severe alcohol, benzodiazepine) can cause seizures or delirium.
• Infections: blood-borne viruses, endocarditis, and skin and soft-tissue infection in people who inject.
• Organ damage: liver disease and cirrhosis, cardiomyopathy, pancreatitis, neuropathy.
• Mental health complications: depression, anxiety, psychosis, and suicide.
• Social consequences: unemployment, criminalisation, isolation, homelessness.
• Neonatal complications in infants exposed in utero.

SUDs tend to be chronic and relapsing, but they are treatable. Severity predicts outcome: severe disorder (six or more criteria), physical dependence, psychiatric comorbidity, and poor social support all predict relapse. Conversely, sustained engagement in treatment, medication where indicated, and recovery-support services improve retention and reduce mortality. The aim is remission and functional recovery, and patients who relapse should be supported to re-enter treatment quickly rather than treated as failures.

Prevention operates at universal, selective, and indicated levels, and is most effective when begun in childhood and adolescence.^[1] Effective elements include reducing exposure, treating comorbid disorders, and strengthening family and school environments.

Screening should be routine rather than reactive. The principles are:

• Ask everyone about substance use; use brief, validated tools.
• A positive screen is not a diagnosis; it triggers assessment.
• Integrate screening into general medical, emergency, mental health, and HIV services.
• Lower the threshold in higher-risk settings and groups.

Where alcohol is concerned, score bands determine the response: brief advice for increasing-risk drinking, and specialist referral for scores suggesting possible dependence.^[14] For other substances, the DAST and single-question screens perform well as initial triage tools.^[3]

Pregnancy, young people, and older adults are addressed in more detail above. Briefly, women and older adults can present with prescription-related misuse, adolescents often show early onset and family involvement helps, and older adults require medication reviews and lower suspicion thresholds. Tailor all management to local guidance.

• A SUD is a clinically significant pattern of use with at least two of eleven DSM-5-TR criteria in twelve months, rated mild, moderate, or severe by symptom count.
• Craving was added and legal consequences removed compared with the older framework, and tolerance and withdrawal are not counted when they occur as part of appropriate medical treatment.
• Systematic screening is more effective than waiting for the patient to raise the subject.
• CAGE, AUDIT, and DAST give graded scores; an AUDIT of eight or more suggests hazardous or harmful use and twenty or more possible dependence.
• Brief motivational interventions of ten to forty-five minutes can be delivered by non-specialists.
• Motivational interviewing works with ambivalence; do not confront.
• Alcohol: benzodiazepines for withdrawal, lorazepam for delirium tremens, thiamine for Wernicke's; acamprosate or naltrexone with counselling for relapse prevention.
• Opioids: offer buprenorphine/naloxone using verified induction and maintenance doses, or methadone through licensed programmes, or extended-release naltrexone; no fixed end date.
• Nicotine: varenicline, combination NRT, or bupropion plus behavioural support; avoid bupropion in seizure risk.
• Cannabis and stimulants: psychosocial first-line; no proven medication.
• Pregnancy: opioid agonist treatment saves lives; balance neonatal withdrawal against untreated addiction.
• Treatment follows the Chronic Care Model: assess, agree goals, treat, monitor, and re-engage after relapse.
• Low-resource practice: rely on screening, brief intervention, and the mhGAP stepped framework.

Emergency medicine drug intoxication and withdrawal; opioid drug overdose; hospital alcohol withdrawal management; blood-borne infections in people who inject drugs; depression; anxiety disorders; post-traumatic stress disorder; health and social care of older adults. Plain-text links only; verified-topic links may be added when the topic registry allows.