Tobacco, cannabis, stimulant and behavioural addictions

• Tobacco remains the most important legally available addictive substance in most countries, and stopping smoking is one of the highest-value interventions in medicine. Behavioural support plus a combination of long-acting and short-acting nicotine replacement therapy (NRT) is a first-line option, as are varenicline, cytisinicline and nicotine-containing e-cigarettes.
• First-line management for cannabis and stimulant use disorders is psychosocial, with medical treatment of acute complications such as psychosis or stimulant toxicity.
• Gambling disorder is the only behavioural addiction recognised in DSM-5-TR. It carries the highest suicide risk of any addictive disorder. Group cognitive behavioural therapy (CBT), with individual CBT as an alternative, is the first-line psychological treatment, and naltrexone can help when therapy alone has not worked.
• Internet gaming disorder is still a proposed diagnosis in DSM-5-TR (conditions for further study), though gaming disorder is recognised in ICD-11. Treatment is similar: CBT, family work, and attention to comorbid depression or anxiety. ^[8]

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

1. Classify tobacco, cannabis, stimulant, gambling and internet gaming problems as substance use or behavioural addictions, and name the diagnostic frameworks that recognise them.
2. Explain how nicotine, tetrahydrocannabinol (THC) and stimulants act in the brain, and how gambling and gaming engage the reward system.
3. Identify the warning signs of nicotine, cannabis and stimulant intoxication and withdrawal, and of disordered gambling and gaming.
4. Choose first-line treatments for a smoker who wants to quit, including correct varenicline dosing, and advise a person who is not yet ready to stop.
5. Outline evidence-based management of cannabis use disorder, stimulant use disorder, gambling disorder and problematic gaming, including when to refer.
6. Assess suicide risk and comorbidity in behavioural addictions and describe harm-reduction and low-resource strategies.

Addictions are grouped here by the substance or behaviour, but the underlying process is similar: the mesolimbic dopamine reward circuit is repeatedly activated, learning is hijacked, and control over the behaviour is lost. Tobacco dependence is a substance use disorder driven by nicotine. Cannabis use disorder (CUD) is a substance use disorder driven by THC and related cannabinoids. Stimulant use disorder is driven by cocaine, methamphetamine or amphetamine. Gambling disorder is a behavioural (non-substance) addiction. Internet gaming disorder is a proposed behavioural addiction.

The editions of the diagnostic systems used here are DSM-5-TR and ICD-11. DSM-5-TR places gambling disorder in a new category of behavioural addictions, noting that gambling resembles substance-related disorders in clinical expression, brain origin, comorbidity, physiology and treatment. Internet gaming disorder appears in DSM-5-TR in the section recommending conditions for further study, together with caffeine use disorder. Gaming disorder is a recognised diagnosis in ICD-11. ^{[7] [8]}

Population figures are quoted here only when they can be traced to an source. The pattern, however, is well described across the sources used. Tobacco smoking is common, causes a large burden of preventable disease, and is over-represented in people with mental illness, in pregnancy, and in lower-income groups. Cannabis is the most commonly used illicit drug in most regions, and use of high-potency products has increased. Stimulant use is a substantial contributor to emergency presentations, including chest pain, psychosis and overdose. Gambling and gaming are now widely accessible online, which means they reach younger people and can be concealed for long periods. Gaming is played by a majority of young adults in many high-income countries, although only a small minority develop problems. ^[8]

Risk is rarely single-factor. The common threads across these addictions are:

• Early onset of use, especially before the brain has finished maturing.
• Family history of addiction or other psychiatric conditions.
• Co-existing mental health problems, particularly depression, anxiety, attention-deficit/hyperactivity disorder (ADHD) and trauma-related disorders.
• Social adversity, poverty, unemployment and isolation.
• Easy access to the substance or to gambling or gaming platforms.
• For cannabis, use of high-potency products and daily or near-daily use.
• For stimulants, an occupational or social culture of use, and the use of stimulants to self-manage fatigue, depression or ADHD.
• For gambling, access to credit, alcohol use, and impulsivity.
• For gaming, social isolation, low mood, and games designed around reward loops.

Nicotine dependence develops quickly in adolescents, which is why tobacco use begun in childhood often becomes lifelong addiction. There is no safe level of smoking and no known protective genotype that makes heavy smoking harmless.

Nicotine. Nicotine binds to nicotinic acetylcholine receptors, especially the alpha-4 beta-2 subtype, increasing dopamine release in the nucleus accumbens. Regular use produces tolerance, and stopping produces a withdrawal syndrome of craving, irritability, low mood, insomnia, poor concentration and increased appetite. Most of the harm, however, comes from the smoke, not the nicotine. ^[1]

Cannabis. THC is a partial agonist at cannabinoid-1 (CB1) receptors. It impairs memory, attention and coordination, and can cause anxiety or transient psychotic symptoms. Heavy or daily use, adolescent onset and high-potency products are the features most strongly associated with dependence and with psychotic outcomes. The mesolimbic dopamine system is modulated by CB1 receptor signalling, which is one reason cannabis can precipitate psychosis in vulnerable people. ^[5]

Stimulants. Cocaine, methamphetamine and amphetamine increase synaptic dopamine and noradrenaline by blocking reuptake and, for amphetamines, increasing release. The result is euphoria, energy, hypervigilance, tachycardia and hypertension. Repeated use leads to tolerance, craving and a dysphoric "crash" on withdrawal. Chronic high-dose use can produce a paranoid psychosis that looks like schizophrenia.

Gambling and gaming. These do not introduce a drug, but they activate the same reward pathways. Intermittent, unpredictable rewards (variable-ratio schedules), near misses, losses disguised as wins, and progression systems produce persistent engagement. The behaviour becomes compulsive, and stopping produces irritability and preoccupation. Sleep loss, neglect of work and relationships, and financial harm follow.

Tobacco dependence shows up in the history: the number of cigarettes smoked, how soon after waking the first cigarette is smoked, previous quit attempts, and withdrawal in past attempts. Briefly asking about smoking at every contact is the most effective population-level strategy. People often smoke more when stressed, depressed or when drinking alcohol, and smoke less in smoke-free settings. ^[1]

Withdrawal from nicotine begins within hours and peaks over two to three days: craving, irritability, frustration, anxiety, depressed mood, difficulty concentrating, increased appetite and insomnia. Withdrawal is the main barrier to quitting, and it is treatable.

Cannabis use disorder shows up as loss of control over use, continued use despite harm, craving, tolerance, cannabis withdrawal (irritability, restlessness, low mood, sleep disturbance, decreased appetite, and sometimes abdominal discomfort), and neglect of other activities. Use may be concealed. Higher-risk patterns include daily use, high-potency products, adolescent onset, and use to manage anxiety or low mood.

Emergency presentations are common: acute anxiety or panic, vomiting (including cannabinoid hyperemesis syndrome in very frequent heavy users), tachycardia and, in younger or susceptible users, an acute psychotic illness with paranoid delusions and hallucinations. Differentiating cannabis-induced psychosis from a primary psychotic illness can be difficult at first contact. ^[5]

Stimulant intoxication presents with dilated pupils, tachycardia, hypertension, hyperthermia, agitation, insomnia, hypervigilance, tremor and possible chest pain. Serious complications include myocardial infarction, arrhythmia, stroke, seizures, rhabdomyolysis and hypertensive emergency. Psychiatrically there may be paranoia, auditory hallucinations, delusions and aggressive behaviour.

Stimulant withdrawal is less medically dangerous than alcohol or benzodiazepine withdrawal but very uncomfortable: a crash of exhaustion, hypersomnia, increased appetite, dysphoria, anhedonia, strong craving and, sometimes, suicidal feelings. It usually peaks over several days.

Chronic use can damage the nose (if snorted), the cardiovascular system and the brain, and can produce a persistent psychotic illness.

Gambling disorder is described clinically by preoccupation with gambling, needing to bet larger amounts for the same excitement, repeated failed attempts to cut back or stop, restlessness or irritability when cutting down, gambling to escape problems or low mood, chasing losses by returning to get even, lying about the extent of gambling, loss of relationships or opportunities, and relying on others for rescue from debts. At least four of these features within 12 months are required by the APA definition. ^[7]

Presentation may be hidden for years. Clues include unexplained debt, borrowing from friends or family, selling possessions, secretiveness about finances, depression, anxiety, and in severe cases suicidal thoughts. ^{[6] [7]}

Internet gaming disorder presents as preoccupation with gaming, withdrawal symptoms (sadness, anxiety, irritability) when unable to play, tolerance (longer sessions needed for satisfaction), unsuccessful attempts to cut down or stop, loss of interest in previously enjoyed activities, continuing despite problems, deception about the amount of play, use of gaming to relieve negative mood, and risking or losing a job or relationship because of gaming. Five or more of these nine features within a year are proposed for the diagnosis. ^[8]

Gaming for several hours a day is not by itself pathology. Distress, impairment and loss of other roles are the distinguishing features.

A particular differential is cannabis-induced psychosis versus schizophrenia. Cannabis-induced psychosis often resolves with abstinence, but a significant minority will go on to receive a schizophrenia spectrum diagnosis. ^[5]

Tobacco. Ask about smoking at every opportunity. Count cigarettes per day and time to first cigarette. Expired carbon monoxide monitoring confirms smoking and can motivate; it is cheap, safe and widely available. Look for smoking-related disease (chronic obstructive pulmonary disease, cardiovascular disease, peripheral vascular disease, cancers) according to symptoms. ^[1]

Cannabis. A supportive interview is the main tool. Urine screening can detect THC metabolites, but it does not measure severity or daily dose. In a first episode of psychosis, or in an unusual clinical picture, test for other substances and for organic causes as clinically indicated. Electrocardiogram and physical examination are prudent in older or medically complex users.

Stimulants. Urine drug screening can help. In an acute presentation check vital signs, electrocardiogram, cardiac enzymes if there is chest pain, creatine kinase if there is agitation or muscle pain, renal function, and core temperature. Mental state examination and risk assessment are essential.

Gambling. Assessment tools include the Problem Gambling Severity Index and the South Oaks Gambling Screen. Assess gambling history, types of gambling, current frequency, medical and psychiatric comorbidity, suicide risk, financial impact, and how gambling affects work, relationships and the law. ^[6]

Gaming. A careful history from the person and, where possible, from family. Ask about duration, neglect of sleep and school or work, mood, and distress. There is no laboratory test.

Tobacco. NICE emphasises identifying and quantifying smoking by how many cigarettes a person smokes and how soon after waking. Combined with the number of previous quit attempts and withdrawal, this is enough to plan treatment. ^[1]

Cannabis use disorder is diagnosed when cannabis use leads to clinically significant impairment or distress, with features such as taking larger amounts or for longer than planned, and a lasting wish or failed attempts to reduce use, spending a lot of time obtaining or recovering from cannabis, craving, failure to fulfil roles, continued use despite social or interpersonal problems, giving up other activities, hazardous use, tolerance and withdrawal. These are the standard criteria, paraphrased here.

Stimulant use disorder has the same structure: impaired control, continued use despite harm, craving, tolerance and withdrawal.

Gambling disorder (APA). At least four of the following in the past year: frequent thoughts about gambling; needing to gamble with increasing amounts to achieve excitement; repeated unsuccessful efforts to control, cut back or stop; restlessness or irritability when trying to cut down or stop; gambling to escape problems or negative mood; chasing losses; lying to conceal gambling; loss of important relationships, educational or occupational opportunities; reliance on others to provide money lost to gambling. ^[7]

Internet gaming disorder (APA proposed). Five or more of nine symptoms over a year: preoccupation; withdrawal; tolerance; unsuccessful control attempts; loss of interest in other activities; continued use despite problems; deception; use to relieve negative mood; risking or losing a relationship or job. ^[8]

Gaming disorder (WHO ICD-11). A pattern of gaming behaviour characterised by impaired control over gaming, increasing priority given to gaming over other activities, and continuation or escalation despite negative consequences. ^[8]

First-line options when combined with behavioural support. NICE advises that the following are more likely to help people succeed: cytisinicline (newly recommended, 2025), a combination of short-acting and long-acting NRT, varenicline, and nicotine-containing e-cigarettes. Bupropion, or a single NRT formulation used alone, is less effective. ^[1]

Dosing and practical points.

• NRT is considered for people aged 12 years or over who smoke and are dependent on tobacco, with behavioural support. ^[1]
• Cytisinicline, varenicline and bupropion should not be offered to people under 18. Cytisinicline should not be offered to people aged 66 or over. ^[1]
• Varenicline dosing from the product label: 0.5 mg once daily for days 1 to 3, 0.5 mg twice daily for days 4 to 7, then 1 mg twice daily from day 8 to the end of treatment. Start 1 to 2 weeks before the quit date, continue for 12 weeks, and consider 12 more weeks at 1 mg twice daily to maintain abstinence. For patients who cannot tolerate it, lower the dose temporarily or permanently to 0.5 mg twice daily. For severe renal impairment (creatinine clearance under 30 ml/min) use 1 mg once daily after 0.5 mg once daily for the first 3 days. Varenicline is a partial agonist at alpha-4 beta-2 nicotinic receptors: it eases withdrawal (agonist effect) while blocking nicotine binding (antagonist effect). ^{[3] [1]}
• Adults should agree a quit date; for varenicline start treatment 1 to 2 weeks before it and reassess shortly before the prescription ends. For NRT, have it ready to start the day before the quit date. For cytisinicline, the quit date is set within the first 5 days of treatment. ^[1]
• In pregnancy, do not simply advise "carry on smoking"; use the NICE pregnancy section, with behavioural support first, and NRT if needed under specialist advice. Varenicline should be avoided in pregnancy as a precaution. ^{[1] [3]}
• Surgery: stopping at any time before surgery has no ill effects, and people who stop in the 8 weeks before surgery benefit significantly. Advise removal of nicotine patches 24 hours before microvascular reconstructive surgery and surgery using vasopressin injections. ^[1]
• Medicines whose levels change when smoking stops: clozapine, olanzapine, theophylline and warfarin; monitor and adjust doses. ^[1]
• E-cigarettes are not licensed as medicines in the UK but are regulated, are likely to be substantially less harmful than smoking, and should not be used alongside continued tobacco smoking. ^[1]

The World Health Organization's 2024 clinical treatment guideline for tobacco cessation in adults provides technical guidance on behavioural and pharmacological treatments for adults, consistent with offering evidence-based behavioural support plus pharmacotherapy. ^[2]

Harm reduction. If a person does not want, or is not ready, to stop in one go, offer choices: cutting down before quitting with licensed nicotine products, smoking reduction using licensed nicotine products, or temporary abstinence using licensed nicotine products. These products can be used as a complete or partial substitute for tobacco in the short or long term. Reassure people that it is better to use them and reduce smoking than to continue at the current level. A quit date within about six weeks is a reasonable target for people cutting down before stopping. ^[1]

Smokeless tobacco. Ask, advise on the health risks (cardiovascular disease, oropharyngeal cancer, periodontal disease), and refer to specialist cessation services, especially for South Asian communities where smokeless tobacco is common. ^[1]

First-line management is psychosocial, in line with NICE's guideline for drug misuse (CG51), which covers psychosocial interventions for cannabis and stimulant misuse. ^{[4] [1]}

Approach:

• Establish rapport without judgement; ask about amount, frequency, potency, route, age at first use, withdrawal, and impact on work, study and relationships.
• Set a shared goal, usually reduction or abstinence, and identify triggers.
• Use motivational interviewing and personalised feedback.
• Offer psychological interventions with evidence in substance misuse: motivational enhancement, cognitive behaviour and coping-skills work, and contingency management with tangible incentives for negative tests. ^[4]
• NICE specifically advises that CBT and psychodynamic therapy focused on drug misuse should not be offered routinely for cannabis misuse, so simpler, structured interventions are usually preferred. ^[4]
• Involve family or partners when the person agrees, especially in adolescents.
• Treat co-existing depression, anxiety, trauma-related disorders, ADHD and psychosis concurrently. ^[4]
• Review regularly; many people improve with brief, repeated interventions.

Cannabis and psychosis. This is the most serious complication to watch for. Cannabis-induced psychosis can be the first expression of an illness that later becomes schizophrenia or bipolar disorder. In a recent systematic review and meta-analysis of patients initially diagnosed with cannabis-induced psychosis, about one in five (20%, 95% confidence interval 15.8 to 29.5%) were later diagnosed with a schizophrenia spectrum disorder, and about one in twenty (5%, 95% confidence interval 2.7 to 6.9%) with bipolar disorder. Cannabis-induced psychosis showed a stronger association with subsequent schizophrenia spectrum disorder than other substance-induced psychoses. ^[5]

Practical implications:

• In a first episode of psychosis in a cannabis user, treat the symptoms (antipsychotic according to local protocol) alongside complete cannabis cessation.
• Do not reassure a young user that cannabis "cannot cause mental illness"; the risk is real, particularly with early onset and high potency.
• Arrange psychiatric follow-up after the acute episode, because that is when the later diagnosis emerges. ^[5]
• Warn against mixing cannabis with other substances, and about the risks of chronic heavy use.

First-line management is psychosocial, in line with NICE's guideline for drug misuse (CG51), which covers psychosocial interventions for stimulant misuse, with medical management of acute complications. ^[4]

As with cannabis, the foundation is a non-judgemental assessment, motivational work, and regular review. The strongest specific recommendations are:

• Contingency management programmes for people who primarily misuse stimulants, with incentives contingent on drug-negative tests. ^[4]
• Behavioural couples therapy for people in close contact with a non-using partner, with at least 12 weekly sessions. ^[4]
• Peer support groups based on 12-step principles, such as Cocaine Anonymous. ^[4]
• Cognitive behavioural therapy focused on drug misuse should not be offered routinely, but evidence-based psychological treatments (in particular CBT) should be considered for comorbid depression or anxiety. ^[4]
• Leave the door open for harm reduction (reducing use, avoiding solitary bingeing, safer routes) for those not ready for abstinence. ^[4]

Medical management of acute intoxication.

• Protect airway, breathing and circulation; monitor temperature, oxygen, electrolytes, renal function and cardiac rhythm.
• Cooling and intravenous fluids for hyperthermia and rhabdomyolysis; benzodiazepines for agitation and seizures; antipsychotics if psychotic agitation is severe.
• Chest pain requires full acute cardiac assessment; stimulant use is a cause of myocardial infarction in young people.
• Do not underestimate suicide risk during the crash phase.

Complications to address. Cardiovascular disease, stroke, chronic nasal or lung injury, weight loss, dental damage, infectious complications from injecting, and persistent psychosis. Treat comorbid ADHD carefully; if stimulant medication is prescribed for ADHD it should be given in a structured, supervised setting.

Gambling disorder is treated as a mental health condition, not a moral failing or a financial problem alone.

NICE recommends a clinician and patient agree the aim of treatment (typically abstinence from gambling), a case formulation and care plan, and a safety plan where there is suicide risk. ^[6]

Psychological treatment (first line).

• Group CBT to reduce gambling severity and frequency, started as soon as possible after diagnosis; with 8 to 10 sessions. Individual CBT (6 to 8 sessions) if the person does not want to join a group or group therapy is not available. ^[6]
• Relapse prevention as part of CBT: recognising triggers, managing high-risk situations, and using blocking tools and stimulus control. ^[6]
• Motivational interviewing to strengthen confidence and commitment to change. ^[6]
• Peer support (for example Gamblers Anonymous and Gam-Anon for families) as an integral part of care. ^{[6] [7]}
• Concurrent treatment of depression, anxiety and substance use, because they both cause and worsen gambling. ^[6]

Pharmacological treatment. There is no drug approved for gambling disorder. NICE suggests considering naltrexone to reduce gambling severity if an appropriate course of psychological therapy has not achieved the desired aims, or if there are repeated relapses despite therapy. It should be started by, or under the supervision of, an appropriately qualified specialist. Baseline and follow-up checks of kidney and liver function are needed, opioids must be excluded before starting and avoided during treatment, and the suggested titration is 25 mg once daily for 3 days then 50 mg once daily for 4 to 6 months, with regular follow-up for side effects such as chest pain or palpitations. ^{[6] [7]}

Practical steps. Discuss abstinence from money as a start: block gambling payments through the bank, use blocking software, self-exclusion from betting shops and online platforms, and transfer control of finances to a trusted person where agreed. Provide debt management, housing and legal advice, and support for families. ^[6]

Suicide. Gambling disorder has the highest suicide risk of all substance use and addictive disorders. About one in two people with gambling problems think about suicide and about one in five attempts suicide. Ask directly about suicidal thoughts at every contact, make a safety plan, and refer urgently when there is immediate risk. ^{[6] [7]}

Gaming problems are treated, but the framework is younger and more debated than for gambling.

• Be aware that excessive gaming can reflect an underlying problem such as depression, anxiety or loneliness; treat that problem first when it is primary.
• Use CBT-based interventions: monitoring of play time, goal setting, stimulus control (remove gaming from the bedroom, use timers), and developing alternative activities and social contact.
• Family or couple sessions help when the person lives with others; parents are partners in change for younger people.
• Address sleep, exercise, and school or work re-engagement.
• Medication has no established role for gaming itself; treat comorbid conditions.
• The evidence base is still developing. The APA notes that a substantial majority of people who play online games do not have the disorder, and the proportion of the general population who might meet proposed criteria is estimated at 0.3 to 1.0%. ^[8]

People with one addiction often have others and often have mental illness. Tobacco smoking is much more common in people with severe mental illness and is a leading cause of their premature death. Treat tobacco in parallel with the other problem rather than waiting for it to "stabilise": NICE recommends specialist mental-health tailored support, of extended duration and intensity, for people with severe mental health conditions, and adjustment of medicines such as clozapine when smoking changes. ^[1]

Cannabis and stimulant use are strongly linked with psychosis. Someone presenting for the first time with either substance and new psychotic symptoms needs psychiatric assessment, not just a drug-service referral.

• Tobacco: cardiovascular disease, stroke, chronic obstructive pulmonary disease, many cancers, peripheral vascular disease, osteoporosis, eye and oral disease, adverse pregnancy outcomes.
• Cannabis: dependence, psychosis, anxiety, cannabinoid hyperemesis syndrome in heavy users, impaired driving and accident risk.
• Stimulants: myocardial infarction, arrhythmia, stroke, seizures, rhabdomyolysis, hyperthermia, malnutrition, dental and nasal damage, persistent psychosis, blood-borne infection if injecting.
• Gambling: debt, bankruptcy, criminal behaviour, relationship breakdown, depression, and suicide.
• Gaming: impaired sleep, academic or occupational failure, social withdrawal, and family conflict.

Prognosis depends on early identification and on treating the whole person. Stopping smoking at any age substantially reduces cardiovascular and cancer risk and improves survival. About one in five patients with cannabis-induced psychosis will later be diagnosed with a schizophrenia spectrum disorder and about one in twenty with bipolar disorder, which is why follow-up after a substance-induced psychosis matters. ^[5] Stimulant recovery often requires several treatment episodes; contingency management improves retention and testing negative. Gambling recovery is possible, but relapse is common and the risk of suicide remains high throughout recovery. For gaming, the long-term outlook is less certain, because the diagnosis and treatments are still being defined.

• Tobacco: ask about smoking at every contact, mass-media and school-based prevention, smoke-free public spaces and workplaces, plain packaging and tax policy, and treatment of tobacco dependence as a routine clinical service. Secondary prevention starts with opportunistic brief advice plus referral. ^[1]
• Cannabis: screen in mental health and primary care, brief advice about potency and frequency, and harm-reduction advice (least harmful routes, avoid driving, do not use in adolescence).
• Stimulants: screen in emergency, psychiatric and sexual health settings; harm-reduction education including safer use and overdose signs; peer-led prevention in high-risk groups.
• Gambling: ask about gambling whenever asking about alcohol, smoking or substances, and in the situations listed in the NICE guideline (mental illness, impulse-control medicines, criminal justice contact, alcohol or substance dependence, homelessness, financial concern, safeguarding concerns or family history). Use direct questions and validated questionnaires, and provide brief motivational interviewing. ^[6]
• Gaming: discuss gaming in routine adolescent and young-adult health checks; focus on sleep, school or work performance, mood, and family functioning, and keep the distinction between engaged play and pathology.

Pregnancy. Tobacco: advise stopping smoking before and during pregnancy; behavioural support first; NRT can be used if needed to maintain abstinence, in line with NICE guidance. Varenicline should be avoided in pregnancy as a precaution. ^{[1] [3]} Cannabis and stimulant use in pregnancy warrants obstetric and mental-health review; avoid moralising but be clear about risks. Do not stop prescribed medicines abruptly without clinical review.

Children and adolescents. Tobacco dependence can begin quickly; NRT may be considered from age 12 with behavioural support; cytisinicline, varenicline and bupropion are not offered under 18. ^[1] Early cannabis and gaming use are associated with worse outcomes, so family involvement and school support matter. Stimulant misuse in young people requires safeguarding review.

Older adults. Varenicline needs dose reduction in severe renal impairment. ^[3] Gambling and gaming problems in older adults are increasingly recognised and can be related to bereavement and social isolation. Screen for depression and suicide.

Severe mental illness. As above, tobacco treatment should be integrated and of appropriate intensity. ^[1] Psychotic illness with concurrent substance use requires coordinated psychiatric and addiction care.

• A basic smoking cessation service can run on expired carbon monoxide monitors, behavioural support and licensed NRT; aim for combination NRT where available. ^[1]
• When varenicline or NRT are unavailable, behavioural support, motivational interviewing and quitlines remain valuable. Self-help materials and telephone support cost little and reach many people.
• Cannabis, stimulant and behavioural addictions are treated mainly by talking therapies; contingency management can be run with modest, immediate, non-cash incentives.
• In settings without psychiatrists, train primary-care clinicians and nurses to ask, advise and assess risk; provide straightforward protocols and referral pathways.
• Prioritise suicide prevention: routine direct questioning, safety planning and prompt referral.
• Record numbers treated so services can be expanded on evidence.

• Tobacco causes a heavy burden of preventable disease; stopping at any age helps. First-line pharmacotherapy with behavioural support is combined NRT, varenicline, cytisinicline or a nicotine-containing e-cigarette.
• Varenicline is taken for 12 weeks, with a one-week titration (0.5 mg once daily, then 0.5 mg twice daily, then 1 mg twice daily), started 1 to 2 weeks before the quit date; a further 12 weeks maintains abstinence.
• Nicotine itself is far less harmful than tobacco smoke; harm reduction is appropriate for people not ready to stop.
• Cannabis use disorder is managed with psychosocial interventions, with careful attention to psychosis risk in young and heavy users.
• About one in five people with cannabis-induced psychosis later receives a schizophrenia spectrum diagnosis and about one in twenty a bipolar diagnosis, so follow-up is essential.
• Stimulant use disorder uses psychosocial interventions: contingency management and behavioural couples therapy are the best supported.
• Gambling disorder is a behavioural addiction with the highest suicide risk of any addictive disorder; group CBT is first line and naltrexone may help after repeated therapy failure.
• Internet gaming disorder is a proposed, not confirmed, diagnosis with criteria requiring five or more of nine features over a year; management centres on CBT, families and comorbidities.
• Always screen for comorbidity and suicide; treat substance and mental health problems together.

Depression; anxiety disorders; adult ADHD; schizophrenia and other psychotic disorders; alcohol use disorder; opioid use disorder; suicide risk assessment and self-harm; cardiovascular and respiratory disease; pregnancy and medicines in pregnancy.