Increasing prevalence of recreational cannabis use among the young population has stimulated debate on the possible effects of acute and long-term use.

To highlight recent knowledge of mechanisms of action, effects on psychomotor and cognitive performance, and health risks associated with cannabis consumption.

A brief review of recent literature on the prevalence of recreational cannabis use, the potency of modern cannabis preparations and the pharmacological actions of cannabis.

Cannabinoids derived from herbal cannabis interact with endogenous cannabinoid systems in the body. Actions on specific brain receptors cause dose-related impairments of psychomotor performance with implications for car and train driving, aeroplane piloting and academic performance. Other constituents of cannabis smoke carry respiratory and cardiovascular health risks similar to those of tobacco smoke.

Cannabis is not, as widely perceived, a harmless drug but poses risks to the individual and to society.

Review commissioned in 1996 by the Department of Health (DOH).

Assess therapeutic profile of cannabis and cannabinoids.

Medline search, references supplied by DOH and others, and personal communications.

Cannabis and some cannabinoids are effective antiemetics and analgesics and reduce intraocular pressure. There is evidence of symptom relief and improved well-being in selected neurological conditions, AIDS and certain cancers. Cannabinoids may reduce anxiety and improve sleep. Anticonvulsant activity requires clarification. Other properties identified by basic research await evaluation. Standard treatments for many relevant disorders are unsatisfactory. Cannabis is safe in overdose but often produces unwanted effects, typically sedation, intoxication, clumsiness, dizziness, dry mouth, lowered blood pressure or increased heart rate. The discovery of specific receptors and natural ligands may lead to drug developments. Research is needed to optimise dose and route of administration, quantify therapeutic and adverse effects, and examine interactions.

Cannabis is commonly regarded as an innocuous drug and the prevalence of lifetime and regular use has increased in most developed countries. However, accumulative evidence highlights the risks of dependence and other adverse effects, particularly among people with pre-existing psychiatric disorders.

To re-evaluate the adverse effects of cannabis in the general population and among vulnerable individuals, including those with serious psychiatric disorders.

A wide-ranging review of the topics related to these issues.

An appreciable proportion of cannabis users report short-lived adverse effects, including psychotic states following heavy consumption, and regular users are at risk of dependence. People with major mental illnesses such as schizophrenia are especially vulnerable in that cannabis generally provokes relapse and aggravates existing symptoms. Health workers need to recognise, and respond to, the adverse effects of cannabis on mental health.

Cannabis policy continues to be controversial in North America, Europe and Australia.

To inform this debate, we examine alternative legal regimes for controlling cannabis availability and use.

We review evidence on the effects of cannabis depenalisation in the USA, Australia and The Netherlands. We update and extend our previous (MacCoun & Reuter, 1997) empirical comparison of cannabis prevalence statistics in the USA, The Netherlands and other European nations.

The available evidence indicates that depenalisation of the possession of small quantities of cannabis does not increase cannabis prevalence. The Dutch experience suggests that commercial promotion and sales may significantly increase cannabis prevalence.

Alternatives to an aggressively enforced cannabis prohibition are feasible and merit serious consideration. A model of depenalised possession and personal cultivation has many of the advantages of outright legalisation with few of its risks.

Tricyclic antidepressants have similar efficacy and slightly lower tolerability than selective serotonin reuptake inhibitors (SSRIs). However, there are no systematic reviews assessing amitriptyline, the reference tricyclic drug, v. other tricyclics and SSRIs directly.

To review the tolerability and efficacy of amitriptyline in the management of depression.

A systematic review of randomised controlled trials (RCTs) comparing amitriptyline with other tricyclics/heterocyclics or with an SSRI.

We reviewed 186 RCTs. The overall estimate of the efficacy of amitriptyline revealed a standardised mean difference of 0.147 (95% CI 0.05–0.243), significantly favouring amitriptyline. The overall OR for dropping out was 0.99 (95% CI 0.91–1.08) and that for side-effects was 0.62 (95% CI 0.54–0.70), favouring the control drugs. With drop-outs included as treatment failures, the estimate of the effectiveness of amitriptyline v. tricyclics/heterocyclics and SSRIs showed a 2.5% difference in the proportion of responders in favour of amitriptyline (number needed to treat 40, CI 21–694; OR 1.12 (95%CI 1.01–1.24)).

Amitriptyline is less well tolerated than tricyclics/heterocyclics and SSRIs, but slightly more patients treated on it recover than on alternative antidepressants.

Health planning should be based on data about prevalence, disability and services used.

To determine the prevalence of ICD–10 disorders and associated comorbidity, disability and service utilisation.

We surveyed a national probability sample of Australian households using the Composite International Diagnostic Interview and other measures.

The sample size was 10 641 adults, response rate 78%. Close to 23% reported at least one disorder in the past 12 months and 14% a current disorder. Comorbidity was associated with disability and service use. Only 35% of people with a mental disorder in the 12 months prior to the survey had consulted for a mental problem during that year, and most had seen a general practitioner. Only half of those who were disabled or had multiple comorbidity had consulted and of those who had not, more than half said they did not need treatment.

The high rate of not consulting among those with disability and comorbidity is an important public health problem. As Australia has a universal health insurance scheme, the barriers to effective care must be patient knowledge and physician competence.

A number of studies have questioned whether the natural course of schizophrenia is more favourable in ‘developing’ than ‘developed’ societies and whether culture is a factor in producing a favourable course.

This prospective study tests the hypothesis that the natural outcome of schizophrenia would be favourable in a Chinese rural area.

We investigated all patients with schizophrenia, including patients who had not received any treatment, among 149 231 rural community population in Xinjin County, Sichuan in 1994. Those patients who had never received treatment were followed up for two years.

Three-quarters of patients with schizophrenia who had not been treated remained symptomatic. As the duration of illness increased, the illness became more serious. The clinical outcome of the drug-treatment group was significantly better than for patients who had not received any treatment.

The natural clinical outcome of schizophrenia in the Chinese rural community was poor, and occupational functioning of patients with schizophrenia was comparatively better. Schizophrenia itself has a specific natural course – antipsychotic drug treatment and psychosocial treatment will produce an improvement in prognosis.

The comparative outcome of psychosis in British Whites and UK African-Caribbeans is unclear. Some report that African-Caribbeans have worse outcome, whereas others claim better symptomatic outcome and a more benign course.

To compare the course, outcome and treatment of psychosis in African-Caribbeans and British Whites in a large multi-centre sample.

A secondary analysis of 708 patients with research diagnostic criteria-defined psychosis from a 2-year, randomised controlled trial of case management. Outcome measures (hospitalisation, illness course, self-harm, social disability and treatment received) were adjusted for socio-economic and clinical differences between groups at baseline using regression analysis.

African–Caribbeans were less likely to have a continuous illness and to receive treatment with antidepressants or psychotherapy.

The outcome of psychosis is complex but differs between UK African–Caribbeans and British Whites. This may reflect risk factors that increase the rate of psychosis in UK African–Caribbeans. Treatment differences require further investigation.

Little research has been carried out on the benefits of intensive case management (ICM) for people with borderline IQ and severe mental illness.

To compare outcome and costs of care of patients with severe psychotic illness with borderline IQ to patients of normal IQ and to assess whether ICM is more beneficial for the former than for the latter.

The study utilises data from the UK700 multi-centre randomised controlled trial of case management. The main outcome measure was the number of days spent in hospital for psychiatric reasons. Secondary outcomes were costs of care and clinical outcome.

ICM was significantly more beneficial for borderline-IQ patients than those of normal IQ in terms of reductions in days spent in hospital, hospital admissions, total costs and needs and increased satisfaction.

ICM appears to be a cost-effective strategy for a subgroup of patients with severe psychosis with cognitive deficits.

Twenty per cent of patients with bipolar affective disorder suffer an illness that responds inadequately to treatment and has a poor outcome. Many patients, but not all, with bipolar disorder show white matter abnormalities on T2-weighted magnetic resonance imaging (MRI).

To explore the hypothesis that white matter abnormalities on MRI are seen more frequently in subjects whose illness has a poor outcome compared with those with a good outcome or controls.

Two groups of age- and gender-matched patients with bipolar disorder (14 with a good outcome and 15 with a poor outcome) and 15 controls, aged 20–65 years, were studied. Axial T2-weighted MRI scans were examined for the presence and severity of white matter abnormalities.

Significantly more poor outcome group members had deep subcortical punctate, but not periventricular, white matter hyperintensities than the good outcome group (P=0.035) or controls (P=0.003) and these abnormalities were of greater severity (P=0.030 and P < 0.014, respectively).

Subcortical white matter lesions are associated with poor outcome bipolar disorder.