Cannabis is the most widely used illicit psychoactive substance globally, and rising potency of delta-9-tetrahydrocannabinol (THC) in modern products has reshaped the clinical picture clinicians now encounter on consult services, in emergency departments, and in outpatient practice. DSM-5-TR groups the cannabis-related diagnoses into Cannabis use disorder, cannabis intoxication, cannabis withdrawal, and several cannabis-induced mental disorders (psychotic, anxiety, sleep, and delirium), all within the substance-related and addictive disorders chapter. The clinical takeaway is twofold: cannabis use disorder is common, frequently underdiagnosed, and amenable to behavioural treatment, while heavy or high-potency use carries a dose-dependent risk of acute psychotic episodes and persistent psychotic illness, particularly in adolescents and individuals with a family history of schizophrenia. There is no FDA-approved pharmacotherapy for cannabis use disorder; psychosocial interventions remain the foundation of care. Recognise Cannabinoid hyperemesis syndrome and acute psychosis as the two cannabis-related presentations most likely to send a patient to the emergency department.

Cannabis is the most widely used psychoactive substance other than alcohol and nicotine in most high-income countries, with use concentrated in adolescents and young adults. Legal and regulatory changes in North America and Europe over the past decade have shifted patterns of use, product potency, and clinical presentations.^[1-2]

Prevalence and use patterns

• Lifetime prevalence of cannabis use in U.S. adults is approximately 49%, with past-year use around 18% in recent National Survey on Drug Use and Health (NSDUH) data.^[1]
• Past-year prevalence of CUD in U.S. adults is approximately 1.5–3%, with lifetime prevalence near 6–9%; rates are roughly twofold higher in adolescents and young adults than in middle-aged adults.^[1,3]
• Approximately 9% of people who ever use cannabis develop CUD; this rises to about 17% among those who begin use in adolescence and approaches 25–50% in daily users.^[3-4]

Age of onset and sex distribution

• Peak age of initiation is 15–24 years, with most CUD diagnoses emerging within 5–10 years of first regular use.^[3]
• Males are diagnosed with CUD at roughly twice the rate of females, although the sex gap has narrowed over the past two decades.^[1,3]

Comorbidity

• CUD shows high comorbidity with other substance use disorders, particularly tobacco and alcohol; co-occurrence with Alcohol use disorder approaches 50% in clinical samples.^[3]
• Mood and anxiety disorders are present in roughly one-third of individuals with CUD; PTSD is overrepresented.^[3,5]
• Heavy adolescent use is associated with a two- to four-fold increased risk of later Schizophrenia spectrum disorders, with the strongest associations for daily high-potency (>10% THC) use.^[6-7]

Key risk factors

• Early age of initiation (before age 16) is the strongest demographic predictor of CUD and of cannabis-related psychosis.^[6-7]
• Daily or near-daily use, use of high-potency products (concentrates, vape oils, edibles with high THC content), and family history of psychotic illness or substance use disorder all increase risk.^[2,6-7]
• Adverse childhood experiences, trauma, and lower socioeconomic status are associated with both initiation and progression to CUD.^[3,5]

Cannabis exerts its psychoactive effects primarily through delta-9-tetrahydrocannabinol (THC), a partial agonist at the cannabinoid CB1 receptor, with secondary contributions from CBD and several minor cannabinoids. The Endocannabinoid system modulates dopaminergic, glutamatergic, and GABAergic transmission across reward, executive, and emotional circuits.^[2,8]

Neurobiology

• CB1 receptors are densely expressed in basal ganglia, hippocampus, cerebellum, prefrontal cortex, and amygdala; activation by THC produces euphoria, altered time perception, memory impairment, motor effects, and anxiety.^[8]
• THC indirectly increases dopamine release in the Nigrostriatal pathway and ventral striatum via disinhibition of GABAergic interneurons, providing the proposed mechanism for both reinforcement and acute psychotomimetic effects.^[2,8]
• Cannabidiol is a negative allosteric modulator at CB1 and has partial 5-HT1A agonism; it does not produce intoxication and may partially attenuate THC-induced psychotomimetic effects, though clinical evidence is mixed.^[8-9]
• Chronic heavy use produces CB1 receptor downregulation in cortical and limbic regions on PET imaging, with partial recovery after approximately 4 weeks of abstinence.^[10]

Structural and functional imaging

• Heavy adolescent use is associated with reduced hippocampal volume and altered prefrontal cortical thickness; causality versus pre-existing vulnerability remains debated.^[6,10]
• Functional MRI studies show altered reward-related activation in ventral striatum and reduced prefrontal control during inhibition tasks in individuals with CUD.^[10]

Genetics

• Heritability of CUD is estimated at 50–60% from twin studies.^[3,11]
• Genome-wide association studies have identified loci near CADM2, FOXP2, and the cannabinoid receptor gene CNR1; polygenic risk for schizophrenia overlaps substantially with risk for CUD and cannabis-induced psychosis.^[11]
• The AKT1 C/C genotype and variants in COMT (Val158Met) have been associated with increased risk of cannabis-induced psychosis in some studies, though replication is inconsistent.^[6,11]

Environmental factors

• Increasing THC potency (mean THC content in U.S. cannabis flower rose from approximately 4% in the 1990s to over 15% in 2020s; concentrates routinely exceed 60–80%) is a central environmental driver of escalating clinical harm.^[2]
• Vaporized and edible high-THC products are associated with increased emergency department visits for acute psychosis, hyperemesis, and paediatric ingestions.^[2,12]

Integrative model

• Current models conceptualize cannabis-related disorders as the result of repeated CB1 activation in a vulnerable nervous system, producing receptor adaptation, reward circuit sensitisation, and (in genetically predisposed individuals) unmasking or precipitation of psychotic illness.^[2,6,8]

DSM-5-TR places cannabis-related disorders within the substance-related and addictive disorders chapter and recognizes cannabis use disorder, cannabis intoxication, cannabis withdrawal, and cannabis-induced mental disorders. The same 11-criterion framework used across substance use disorders applies.^[13]

Cannabis use disorder — diagnostic criteria

• A problematic pattern of cannabis use leading to clinically significant impairment or distress, with at least 2 of 11 criteria within a 12-month period.^[13]
• Criteria span four domains:
  • Impaired control (using more than intended, persistent desire or unsuccessful efforts to cut down, time spent obtaining or recovering, craving).^[13]
  • Social impairment (failure to fulfil major role obligations, continued use despite interpersonal problems, activities given up).^[13]
  • Risky use (use in physically hazardous situations, continued use despite knowledge of physical or psychological harm).^[13]
  • Pharmacologic criteria (tolerance, withdrawal).^[13]
• Severity is based on symptom count: mild (2–3), moderate (4–5), severe (6 or more).^[13]

Cannabis intoxication

• Recent cannabis use plus clinically significant behavioural or psychological changes (impaired motor coordination, euphoria, anxiety, sensation of slowed time, impaired judgment, social withdrawal) developing during or shortly after use.^[13]
• At least two physical signs within 2 hours of use: conjunctival injection, increased appetite, dry mouth, or tachycardia.^[13]
• Symptoms are not attributable to another medical condition or substance.^[13]
• Specify if "with perceptual disturbances" (intact reality testing during intoxication-related hallucinations or illusions).^[13]

Cannabis withdrawal

• Cessation of cannabis use that has been heavy and prolonged (usually daily or near-daily over months).^[13]
• At least 3 of the following developing within approximately 1 week: irritability or aggression, nervousness or anxiety, sleep disturbance (often with vivid dreams), decreased appetite or weight loss, restlessness, depressed mood, and at least one physical symptom such as abdominal pain, tremor, sweating, fever, chills, or headache.^[13]
• Symptoms cause clinically significant distress or impairment and are not explained by another condition.^[13]
• Onset typically 24–72 hours after cessation, peak at 1 week, resolution by 2–3 weeks; sleep disturbance can persist longer.^[13-14]

Cannabis-induced mental disorders

• Cannabis-induced psychotic disorder: hallucinations or delusions emerging during or shortly after intoxication or withdrawal, with evidence the symptoms are substance-related and not better explained by an independent psychotic disorder.^[13]
• Cannabis-induced anxiety disorder, cannabis-induced sleep disorder, and cannabis intoxication delirium are separately codable.^[13]
• A diagnosis of cannabis-induced psychotic disorder requires symptoms beyond what is typical for cannabis intoxication and resolution generally within 1 month of abstinence; persistence beyond that points toward a primary psychotic disorder.^[13]

ICD-11 differences:

• ICD-11 separates "harmful pattern of cannabis use" from "cannabis dependence," preserving a dichotomy DSM-5-TR collapsed into a single spectrum diagnosis with severity specifiers.^[15]
• ICD-11 introduces a single-episode "harmful use" category, useful for capturing acute harm without committing to a chronic disorder label.^[15]

Acute intoxication

• Psychological: euphoria, relaxation, altered time perception (time often slows subjectively), heightened sensory perception, increased sociability, mild perceptual distortions; at higher doses anxiety, panic, paranoia, depersonalisation, derealisation, transient psychotic symptoms.
• Cognitive: impaired short-term memory, attention, psychomotor coordination, reaction time, and executive function; effects persist for several hours and may extend beyond subjective "high."
• Physical: conjunctival injection ("red eyes"), dry mouth, increased appetite ("the munchies"), tachycardia, orthostatic hypotension, mild ataxia, slowed reflexes; pupils usually normal or slightly dilated.
• High-potency or synthetic cannabinoid intoxication: severe agitation, hyperthermia, seizures, hypertensive crisis, acute kidney injury, and arrhythmias have been reported, particularly with synthetic cannabinoid receptor agonists ("Spice," "K2") which act as full CB1 agonists ^[16].

Cannabinoid hyperemesis syndrome (CHS)

• Triad of long-term heavy cannabis use, recurrent cyclical vomiting, and symptom relief with hot bathing or showering; nausea and abdominal pain are prominent and often refractory to standard antiemetics ^[17].
• Frequently misdiagnosed for years as cyclic vomiting syndrome or functional gastrointestinal disorder; cessation of cannabis is curative but symptoms may take weeks to resolve.
• Pathophysiology is incompletely understood; hypotheses involve CB1 receptor dysregulation in the enteric nervous system and hypothalamic-pituitary effects ^[17].

Chronic use features

• Tolerance to euphoric, cognitive, and cardiovascular effects develops within days to weeks of regular use; cross-tolerance with synthetic cannabinoids occurs.
• Withdrawal (described above) drives a substantial portion of relapse and is often underestimated by clinicians; sleep disturbance and irritability are the most persistent features ^[14].
• Amotivational syndrome — a controversial construct describing apathy, blunted goal-directed behaviour, and reduced productivity — overlaps substantially with depression, withdrawal, and confounding by social factors; current evidence does not support it as a discrete clinical entity, though residual cognitive effects in heavy adolescent users are well documented ^[10].
• Respiratory effects: chronic bronchitis, cough, sputum production; lung cancer risk remains uncertain after adjustment for tobacco co-use.
• Cardiovascular: increased risk of myocardial infarction in the hour following use, particularly in those with pre-existing coronary disease.

Other substance-related disorders

• Alcohol use disorder, stimulant use disorder, opioid use disorder, and sedative-hypnotic use disorder commonly co-occur with CUD; up to 50% of people with CUD have a concurrent other substance use disorder ^[3]. Toxicology and detailed history are essential, since cannabis intoxication can mask or mimic features of other intoxications and withdrawals.
• Synthetic cannabinoid intoxication: produces a clinical picture far more severe than natural cannabis (severe agitation, psychosis, seizures, organ injury) and is undetectable on standard urine drug screens for THC; clinicians should suspect it in users presenting with disproportionate toxicity ^[16].

Primary psychiatric disorders

• Primary psychotic disorders (schizophrenia spectrum disorders): cannabis-induced psychotic disorder is distinguished by close temporal relationship to use, prominent visual phenomena, and typically rapid resolution (days to weeks) with abstinence. Persistence of psychotic symptoms beyond approximately one month of abstinence should prompt re-diagnosis as a primary psychotic disorder ^[6].
• Anxiety and panic disorders: cannabis-induced anxiety often resolves within hours of intoxication or within weeks of cessation; persistent anxiety despite confirmed abstinence suggests a primary anxiety disorder.
• Major depressive disorder and bipolar disorder: withdrawal-related depressed mood and anhedonia overlap clinically; a 2–4 week observation period of abstinence is generally needed before diagnosing a primary mood disorder.
• ADHD: cognitive impairment from chronic cannabis use can mimic ADHD; conversely, untreated ADHD is a strong risk factor for CUD. Re-assessment after sustained abstinence is essential.

Medical mimics

• Cannabinoid hyperemesis syndrome must be distinguished from cyclic vomiting syndrome, gastroparesis, bowel obstruction, pancreatitis, and adrenal insufficiency; the relief-with-hot-water sign is suggestive but not pathognomonic ^[17].
• Acute intoxication-related tachycardia and chest pain may mimic acute coronary syndrome, pulmonary embolism, or thyrotoxicosis; cardiac workup remains indicated when clinically warranted.
• Cannabis-induced anxiety with depersonalisation may be mistaken for temporal lobe epilepsy, hyperventilation syndrome, or vestibular disorders.

Caution in adolescents

• Distinguishing primary versus substance-induced psychiatric illness is particularly difficult in adolescents; prodromal psychotic states, mood disorders, and emerging personality disorders frequently coexist with early cannabis use and require longitudinal assessment rather than single-visit diagnosis.

History

• Quantify use across dimensions: age of first use, age of regular use, current frequency (days per week, episodes per day), route (smoked joints, blunts, pipes, bongs, vaporised, edibles, dabs/concentrates), product type (herbal flower, hash, oil, edibles, synthetic cannabinoids), and estimated potency (THC%, CBD content where known).
• Screen all 11 DSM-5-TR criteria explicitly; patients rarely volunteer loss of control or craving without prompting. Time since last use, prior periods of abstinence, treatment history, and withdrawal experiences should be documented.
• Comprehensive substance history: tobacco (co-use is the rule), alcohol, stimulants, opioids, sedative-hypnotics, hallucinogens, and synthetic cannabinoids. Note that vaping cannabis is increasingly common among adolescents and may be underreported.
• Psychiatric history with attention to psychosis, mood, anxiety, trauma exposure (post-traumatic stress disorder), ADHD, and personality disorders; family history of psychosis is particularly relevant given gene-environment interaction risk ^[6].
• Medical history including cardiovascular disease, respiratory illness, recurrent vomiting, pregnancy and lactation status, and current medications (especially CYP3A4 substrates and warfarin).
• Social context: education, employment, housing, legal status, relationships, finances; ask about driving under the influence of cannabis given its substantial road-traffic risk.

Screening and structured tools

• CUDIT-R (Cannabis Use Disorders Identification Test–Revised): an 8-item screening instrument with a cut-off of ≥8 suggesting probable CUD; well-validated in primary care and community settings ^[18].
• ASSIST (Alcohol, Smoking and Substance Involvement Screening Test): WHO-endorsed multi-substance screen useful for adolescents and primary care.
• Severity of Dependence Scale (SDS): brief 5-item measure with sound psychometrics for cannabis.

Examination and investigations

• Mental state examination: appearance, behaviour, mood, affect, thought form and content (assess for paranoid ideation, delusions, hallucinations), cognition (orientation, attention, memory, executive function), insight, and judgement.
• Physical examination: conjunctival injection, tachycardia, blood pressure (assess for orthostatic change), respiratory examination, abdominal examination if CHS suspected.
• Urine drug screen: immunoassay for THC-COOH (the inactive metabolite) detects use up to several days after a single exposure and several weeks after chronic heavy use; it does not measure impairment and cannot distinguish acute from past use ^[19].
• Synthetic cannabinoids are not detected by standard THC immunoassays — specialised gas chromatography–mass spectrometry panels are required and are not routinely available.
• Pregnancy test in all reproductive-age women presenting with cannabis use, given prenatal cannabis exposure risks.
• ECG if cardiovascular symptoms or stimulant co-use; baseline liver function tests if pharmacotherapy is being considered.

Risk and motivation

• Assess risk of harm to self and others, including driving, occupational hazards (operating machinery), parenting capacity, and risks during pregnancy.
• Motivation and readiness to change should guide intervention intensity; stages-of-change framing (precontemplation through maintenance) remains a useful clinical heuristic despite limited evidence as a treatment-matching algorithm.

Treatment of cannabis use disorder is grounded in psychosocial interventions; no pharmacotherapy is currently approved by major regulators for CUD, and pharmacological options remain off-label and adjunctive ^[20].

General principles

• Treatment is voluntary in most contexts but should be offered routinely whenever CUD is identified, including in primary care and general psychiatric settings. Brief intervention may be sufficient for mild CUD; moderate-to-severe CUD warrants structured psychotherapy.
• Goals should be negotiated with the patient: abstinence is associated with the best long-term outcomes, but harm reduction (reduced frequency, switching from smoked to vaporised forms, avoiding high-potency products, eliminating driving under influence) is a legitimate intermediate goal, particularly for those unable or unwilling to abstain.
• Co-occurring psychiatric disorders should be treated concurrently rather than sequentially; the older insistence on "sobriety first" is not evidence-based and often results in worse outcomes for both conditions.

Psychosocial interventions (first-line)

• CBT: the most extensively studied modality for CUD, with effect sizes in the small-to-moderate range for reduced use and increased abstinence. Typical protocols deliver 8–14 sessions covering functional analysis of use, coping skills, drug refusal, problem-solving, and relapse prevention ^[21].
• MET: 2–4 sessions of motivational interviewing combined with personalised feedback; effective particularly for those ambivalent about change. MET combined with CBT outperforms either alone in several randomised controlled trials.
• CM: provides escalating reinforcers (typically vouchers) contingent on cannabis-negative urine specimens; produces the largest within-treatment effect sizes of any CUD intervention but with poor maintenance of gains after reinforcement is withdrawn ^[22].
• Combined CBT + MET + CM yields the strongest evidence for adult CUD; effect sizes are modest and relapse rates remain high (50–70% within 6 months of treatment completion).
• Family-based therapies (multidimensional family therapy, family-focused CBT) are first-line for adolescents and outperform individual therapy in this population.
• Mindfulness-based relapse prevention and acceptance and commitment therapy show promise in smaller trials but evidence base is less mature.

Pharmacotherapy (off-label, adjunctive)

• No medication is approved for CUD; trials have explored numerous agents with generally disappointing results. Pharmacotherapy should be considered adjunctive to psychosocial treatment, not a substitute.
• NAC 1200 mg twice daily: positive trials in adolescents have not consistently replicated in adults; generally well tolerated and reasonable to offer where psychosocial treatment alone has failed ^[23].
• Gabapentin 1200 mg/day: small trials suggest modest reductions in use and withdrawal symptoms; limited evidence base.
• Topiramate, naltrexone, buspirone, varenicline, and bupropion have all been studied with negative or inconsistent results; none can be recommended routinely.
• Dronabinol (oral THC) and nabilone have shown modest benefit for withdrawal symptoms in inpatient settings but agonist substitution as a CUD treatment strategy remains investigational and contentious.
• Cannabidiol (CBD) at high doses (400–800 mg/day) has emerging evidence from one phase 2 trial for reducing cannabis use; further trials are ongoing ^[9].
• Treat comorbid disorders with standard agents: SSRIs for depression and anxiety, second-generation antipsychotics for psychosis, stimulants for ADHD (with appropriate caution and monitoring).

Management of intoxication and acute presentations

• Uncomplicated cannabis intoxication is self-limiting and managed supportively in a calm, low-stimulus environment with reassurance; symptoms resolve within hours.
• Severe intoxication with agitation or panic: benzodiazepines (lorazepam 1–2 mg orally or intramuscularly) are first-line; antipsychotics are reserved for prominent psychotic features or failure of benzodiazepines.
• Synthetic cannabinoid toxicity requires aggressive supportive care, including airway protection, treatment of hyperthermia, seizure management, and monitoring for acute kidney injury and rhabdomyolysis ^[16].
• Cannabinoid hyperemesis syndrome: standard antiemetics (ondansetron, metoclopramide) are usually ineffective; topical capsaicin cream applied to the abdomen, haloperidol, and benzodiazepines have shown benefit in case series. Definitive treatment is cessation ^[17].

Management of withdrawal

• Cannabis withdrawal is rarely medically dangerous and is usually managed in the outpatient setting with reassurance, sleep hygiene advice, and short-term symptomatic treatment.
• Insomnia: short courses of low-dose mirtazapine or zopiclone may help; chronic benzodiazepine use should be avoided.
• Anxiety and irritability: brief use of low-dose benzodiazepines may be considered for severe symptoms but is rarely necessary.
• Inpatient detoxification is seldom required except where comorbid use of alcohol, opioids, or benzodiazepines requires medically supervised withdrawal.

Cannabis is sometimes characterised in lay discourse as a uniformly "safe" substance, but the evidence base documents a range of substantive harms, particularly with regular, heavy, early-onset, or high-potency use ^[2,8].

Mental health harms

• Psychosis: a robust dose-response relationship exists between cannabis use and risk of psychotic disorders; daily use of high-potency cannabis (THC ≥10%) is associated with a roughly 3–5-fold increased risk of first-episode psychosis in case-control studies, with population-attributable fractions of 30–50% in some European urban centres ^[7]. Causality remains contested but evidence is consistent with a causal contribution in vulnerable individuals.
• Depression and suicidality: regular cannabis use in adolescence is associated with modestly increased risk of depression and suicidal ideation in young adulthood; effect sizes are smaller than for psychosis and confounding is harder to exclude.
• Anxiety: bidirectional relationship; cannabis is often used to self-medicate anxiety but heavy use independently predicts incident anxiety disorders.
• Cognitive effects: heavy adolescent cannabis use is associated with measurable deficits in verbal learning, memory, attention, and executive function that may persist after abstinence; effects in adult-onset users are smaller and largely reverse with sustained abstinence ^[10].

Physical health harms

• Respiratory: chronic bronchitis, cough, sputum, wheeze; risk of chronic obstructive pulmonary disease is intermediate between tobacco and non-smokers in most studies but methodologically difficult to isolate from tobacco co-use.
• Cardiovascular: increased risk of acute myocardial infarction in the hour following use; increased risk of stroke and arrhythmia, particularly in young users.
• Cannabinoid hyperemesis syndrome (described above): a substantial and under-recognised cause of recurrent emergency department presentations ^[17].
• Cancer: lung cancer risk is uncertain after adjustment for tobacco; testicular germ-cell tumours show a modest association in some studies.
• Accidents: cannabis approximately doubles the risk of motor vehicle collision per use occasion; concurrent alcohol use multiplies risk.

Other harms

• Educational and occupational: heavy adolescent use is associated with lower educational attainment, reduced employment, and lower income in adulthood; reverse causation and confounding are partial but not complete explanations.
• Social: relationship strain, parenting concerns, legal consequences in jurisdictions where use remains criminalised.
• Edibles pose particular acute toxicity risk due to delayed onset, leading to repeated dosing and severe intoxication; paediatric accidental ingestions have risen substantially in jurisdictions with legalised commercial cannabis ^[12].

Limitations of the evidence

• Much of the cannabis literature relies on observational cohorts vulnerable to residual confounding, recall bias, and selection effects; randomised trial data are limited largely to treatment outcomes.
• THC potency has risen substantially over recent decades (from ~3% in the 1980s to >15% in many contemporary products, with concentrates exceeding 70%), so older studies may underestimate contemporary risk.
• Rapid commercial expansion (legal cannabis markets, novel products such as edibles, dabs, and vape concentrates) outpaces epidemiological surveillance; harms data lag behind product innovation.
• Synthetic cannabinoid products fall outside conventional THC measurement and surveillance entirely.
• Most CUD treatment trials have short follow-up (12–24 weeks) and high relapse rates; long-term outcome data are sparse.

Adolescents

• Adolescence is the highest-risk period for both initiation and progression to CUD; brain maturation continues into the mid-twenties and is plausibly more vulnerable to cannabinoid disruption.
• Early onset (before age 16) approximately doubles the risk of subsequent CUD, psychosis, and cognitive impairment compared with adult-onset use.
• Treatment of choice is family-based therapy (multidimensional family therapy, family-focused CBT) supplemented by school and community engagement; pharmacotherapy has very limited evidence in this group.
• Confidentiality and assent considerations differ by jurisdiction; clinicians should be familiar with local mental health and child protection statutes.

Pregnancy and lactation

• Cannabis is the most commonly used illicit substance in pregnancy; prevalence has risen with declining perceived risk and legalisation ^[24].
• Prenatal cannabis exposure is associated with low birth weight, preterm birth, and small-for-gestational-age, with effect sizes comparable to those for tobacco; associations with longer-term neurodevelopmental outcomes are less certain.
• THC and metabolites cross the placenta and enter breast milk, where they persist for several days; concentrations in breast milk approximate maternal plasma levels.
• All major obstetric and paediatric professional bodies advise complete abstinence during pregnancy and breastfeeding; cessation should be supported with non-pharmacological interventions as first-line.

Patients with psychotic disorders

• Cannabis use accelerates onset of first-episode psychosis by approximately 2–3 years and is associated with more frequent relapses, more hospital admissions, and poorer functional outcomes in established schizophrenia ^[6].
• Cessation in early psychosis improves trajectory; cannabis use disorder should be addressed alongside antipsychotic treatment, not deferred until "stability" is achieved.
• High-potency products carry the greatest psychotogenic risk ^[7].

Older adults

• Cannabis use among adults aged 65+ has risen substantially in jurisdictions with medical or recreational legalisation, often for chronic pain, insomnia, or anxiety.
• Older adults are more vulnerable to orthostatic hypotension, falls, drug interactions (particularly with warfarin via CYP3A4/CYP2C9 effects), and cognitive impairment.

Medical cannabis users

• Patients prescribed cannabinoids for chronic pain, multiple sclerosis spasticity, chemotherapy-induced nausea, or treatment-resistant epilepsy (childhood Dravet and Lennox-Gastaut syndromes, where pharmaceutical CBD has regulatory approval) ^[9] are not exempt from CUD risk.
• Indication for medical use does not protect against the development of CUD criteria, and dual recreational/medical use patterns are common.

Course

• Most lifetime cannabis users do not progress beyond experimental or occasional use and remit spontaneously by their mid-twenties ^[4].
• Approximately 10% of lifetime users will at some point meet criteria for CUD; this rises to 17% among those who begin use before age 18 and 25–50% among daily users ^[4,8].
• Among treatment-seekers, abstinence rates at 12 months are typically 15–30%; reduction in use without abstinence is more common.
• Multiple treatment episodes are typical; cumulative effect of repeated treatment exposures is favourable.

Prognostic factors

• Better prognosis: later age of onset, less frequent use, lower potency products, fewer comorbid disorders, stronger psychosocial supports, stable employment and housing, longer abstinence at treatment entry.
• Worse prognosis: early-onset use, daily high-potency use, comorbid psychosis or severe mood disorder, polysubstance use (particularly tobacco), social adversity, and ongoing legal involvement.

Mortality

• Cannabis-attributable mortality is substantially lower than for alcohol, opioids, or tobacco; deaths are usually indirect (motor vehicle collisions, suicide associated with psychosis or depression, complications of CHS) rather than from acute toxicity.
• Synthetic cannabinoid products are an exception, with documented direct fatalities from cardiac, renal, and central nervous system toxicity ^[16].

When to escalate or refer urgently

• Acute psychosis with agitation, command hallucinations, or risk of harm to self or others — refer to acute psychiatric services.
• Suspected synthetic cannabinoid toxicity (severe agitation, hyperthermia, seizures, hypertension, chest pain) — emergency medical assessment.
• Acute cardiac symptoms in any cannabis user — emergency department evaluation, particularly within an hour of use.
• Suspected cannabinoid hyperemesis syndrome with dehydration, electrolyte disturbance, or inability to tolerate oral intake — emergency department for rehydration and symptomatic management ^[17].
• Suicidal ideation with plan or intent — emergency psychiatric assessment.
• Pregnancy with ongoing heavy use — urgent referral for obstetric and addiction-medicine care.
• Children with suspected accidental cannabis edible ingestion — emergency paediatric assessment given risk of severe respiratory depression.

Safety considerations in management

• Driving: counsel all users that cannabis impairs driving for at least 3–4 hours after smoking and longer after edibles; legal blood/oral fluid THC limits apply in most jurisdictions.
• Occupational: safety-sensitive occupations (transport, machinery, healthcare) require explicit discussion; abstinence is generally required.
• Storage: edible products should be kept inaccessible to children and pets; clear labelling reduces accidental ingestion.
• Concurrent prescribing: caution with warfarin, certain antiepileptics, and any medication with narrow therapeutic index metabolised by CYP3A4 or CYP2C9.

Cannabis and psychosis — causality

• Whether cannabis causes psychosis or is merely associated with it remains debated. Mendelian randomisation studies, dose-response consistency, biological plausibility (CB1-mediated effects on dopamine and glutamate signalling), and replication across cohorts support a contributory causal role, particularly for high-potency products ^[6-7]. Critics emphasise residual confounding by socioeconomic status, polysubstance use, and reverse causation in genetically vulnerable individuals. Current consensus among major clinical bodies is that cannabis is a contributory but not sole cause of psychosis in a subset of users.

Medical cannabis

• The evidence base for medical cannabis is mature for only a narrow set of indications: childhood epilepsies (Dravet, Lennox-Gastaut, where pharmaceutical CBD has regulatory approval), chemotherapy-induced nausea (where synthetic cannabinoids are approved), and multiple sclerosis spasticity (nabiximols approved in several jurisdictions) ^[9]. Evidence for chronic pain is mixed; evidence for anxiety, sleep, post-traumatic stress disorder, and many other commonly cited indications is weak or absent.
• Wide divergence exists between regulatory medical-cannabis programmes (heterogeneous in product standardisation, prescriber training, and indications permitted) and the evidence base from controlled trials.

Legalisation and public health

• Public health outcomes following cannabis legalisation in jurisdictions such as several US states, Canada, Uruguay, and parts of Europe remain a subject of active study. Documented effects include increased adult use, increased cannabis-related emergency department presentations (particularly for paediatric edibles, CHS, and synthetic cannabinoid toxicity), and rising potency ^[12]. Effects on adolescent use have been variable; the predicted dramatic increases in youth use have not consistently materialised, though daily use among young adults has risen.
• Effects on illicit market displacement, criminal justice burden, tax revenue, and impaired driving prevalence are jurisdiction-specific and evolving.

Synthetic cannabinoids

• The proliferation of synthetic cannabinoid receptor agonists ("Spice," "K2," and successor compounds) presents a distinct and more dangerous problem than natural cannabis. Their full-agonist activity at CB1 produces a clinical syndrome resembling severe stimulant intoxication rather than classical cannabis intoxication; deaths have been documented ^[16]. Regulatory frameworks have struggled to keep pace with rapidly modified analogues.

Cannabis use during pregnancy

• Some patients and clinicians regard cannabis as a "natural" alternative to pharmacotherapy for pregnancy-related nausea, anxiety, or insomnia. Current evidence does not support safety, and all major obstetric bodies advise abstinence; counselling should be non-judgemental but unambiguous ^[24].

Amotivational syndrome

• The construct of a discrete amotivational syndrome attributable specifically to cannabis remains contested. Observed apathy, blunted goal-directed behaviour, and reduced engagement substantially overlap with depression, withdrawal, social adversity, and pre-existing personality traits. Most current researchers regard it as a non-specific behavioural pattern rather than a distinct cannabis-induced syndrome.

1. Approximately 10% of lifetime cannabis users develop CUD; this rises to 17% in those starting before age 18 and 25–50% in daily users ^[4,8].
2. Cannabis withdrawal is recognised in DSM-5-TR and ICD-11: irritability, sleep disturbance, anxiety, reduced appetite, restlessness, depressed mood, and physical symptoms; onset 24–72 hours after cessation, peak at 1 week, resolution by 2–3 weeks ^[14].
3. The DSM-5-TR criteria for CUD comprise 11 items grouped into impaired control, social impairment, risky use, and pharmacological criteria; ≥2 within 12 months meets diagnosis, with severity by count (2–3 mild, 4–5 moderate, ≥6 severe) ^[13].
4. High-potency cannabis (THC ≥10%) shows a dose-response relationship with first-episode psychosis; daily high-potency use is associated with a 3–5-fold increased risk ^[7].
5. Cannabinoid hyperemesis syndrome — recurrent vomiting in chronic heavy users, characteristically relieved by hot bathing; standard antiemetics are ineffective and cessation is curative ^[17].
6. No pharmacotherapy is approved for CUD; first-line treatment is psychosocial — CBT + MET, with contingency management adjunctive for adults and family-based therapy first-line for adolescents ^[20-21].
7. Synthetic cannabinoids ("Spice," "K2") cause severe agitation, seizures, hyperthermia, and organ injury; they are not detected by standard THC immunoassays ^[16].
8. Urine drug screens detect THC-COOH for days after single use and weeks after chronic heavy use; positive results do not indicate current impairment ^[19].
9. Pharmaceutical CBD has regulatory approval for treatment-resistant childhood epilepsy syndromes (Dravet, Lennox-Gastaut, tuberous sclerosis); evidence for other commonly claimed indications is weak ^[9].
10. Prenatal cannabis exposure is associated with low birth weight and preterm birth; major obstetric bodies recommend complete abstinence during pregnancy and lactation ^[24].

This article was prepared as an educational reference for trainee psychiatrists and allied mental health professionals; it does not constitute personalised clinical advice. The author reports no relevant financial relationships with the pharmaceutical or cannabis industries. Evidence is current to the date of preparation; readers should consult contemporary guidelines and primary literature before applying any recommendation to an individual patient. Local regulatory, legal, and prescribing frameworks vary substantially and take precedence over generic clinical guidance.