More MS news articles for Jan 2002

Cannabis: For and against

BMJ 2002;324:105-108 ( 12 January )
Education and debate

Cannabis control: costs outweigh the benefits

Alex Wodak and colleagues argue that the costs - to health, and fiscal and social - of controlling cannabis are greater than any benefits. In opposition, Colin Drummond lists the potential dangers of decriminalisation.


Alex Wodak, director, (a) Craig Reinarman, professor, (b) Peter D A Cohen, director. (c)

(a) Alcohol and Drug Service, St Vincent's Hospital, Darlinghurst, NSW 2010, Australia,
(b) Department of Sociology, University of California, Santa Cruz, CA 95064, USA,
(c) Center for Drug Research, University of Amsterdam, 1091 GM Amsterdam, Netherlands

Current debates on cannabis policy are dominated by attempts to establish the potential health costs of use of cannabis.(1) While accurate assessment of the potential harms of cannabis is desirable, it is at least as important to estimate the costs - which are usually ignored - of current cannabis controls.

High costs of control noted decades ago

Perhaps doctors have often led the search for less harmful drug policies because the premier axiom of medicine is "first, do no harm." In 1893 Britain's Indian Hemp Drugs Commission concluded that excessive use of cannabis was uncommon and that moderate use produced practically no ill effects. In 1926, Sir Humphrey Rolleston, then president of the Royal College of Physicians, chaired a committee that recommended against criminalising opiates.(2) Similarly, Dr W C Woodward, counsel to the American Medical Association, testified in Congress in 1937 to the lack of evidence justifying criminalisation of cannabis(3) and several other commissions in Britain, Canada, and the United States have come to similar conclusions.(4) In 1972, an American presidential commission concluded that marijuana "does not warrant" the harmful consequences of "criminal stigma and threat of incarceration."(5) In 1978, President Carter told Congress that "penalties against the use of a drug should not be more damaging to an individual than the use of a drug itself; and where they are they should be changed. Nowhere is this more clear than in the laws against the possession of marijuana."(6) Unfortunately, little has changed since President Carter uttered these words. The UK Police Foundation's review of cannabis policy in 2000 was the most recent senior international committee to reach the same verdict: "Our conclusion is that the present law on cannabis produces more harm than it prevents."(7)

Social costs

Beyond the substantial fiscal costs of enforcing the prohibition of cannabis, the social costs of such policies are considerable. Around the world each year, the lives, education, and careers of hundreds of thousands of people are damaged by the stigmatising experience of arrest. Families face lost incomes and emotional stress. Many cannabis users are already socially disadvantaged, so for them criminal penalties for possession of cannabis often entail additional costs, including disruption of relationships and loss of housing and employment.(8) Current cannabis controls drive a wedge between parents and their children, health professionals and their patients, teachers and their students, and police and their communities. It is impossible for the many young people who use cannabis today to obtain reliable information about the concentration of psychoactive ingredients or the purity of samples they purchase, or even about less harmful ways of using the drug. Consequently, current cannabis policies are inimical to desirable public health outcomes.

Other serious costs are borne by communities. Despite its criminalisation, the use of cannabis has become so normalised that it is seen throughout most Western nations. Prohibition in the face of strong and consistent demand inevitably results in supplies being provided from illegal sources. The unregulated black market brings consumers of cannabis into direct contact with sellers of other illicit drugs. For example, in identical surveys of random samples of experienced marijuana users, 55% of respondents in San Francisco reported that they could buy other illicit drugs where they bought cannabis. In Amsterdam, where cannabis sales are regulated and rarely attract criminal sanctions, only 17% could get other illicit drugs from their source of cannabis.(9) Allocating police to enforce the laws against cannabis reduces resources available to enforce laws against more serious crimes. The riches available in black markets increase the risk of serious corruption. During the last decade, royal commissions in two Australian jurisdictions concluded that police corruption was rampant and linked to drug prohibition.(10)

Liberalising control does not increase use

The justification for cannabis prohibition is that it is supposed to reduce demand and supply, thereby reducing use and thus overall adverse health consequences. But demand, supply, and use have all varied widely over time, quite irrespective of controls. Evidence suggests that use is not increased by less intensive control. In the 11 American states that effectively decriminalised cannabis use in the 1970s, use has not risen beyond that experienced by comparable states in which it is prohibited.(11) Similarly, the Netherlands for all intents and purposes decriminalised cannabis 25 years ago, but the prevalence there has remained roughly parallel to that in Germany and France and well below that in the United States.(12)

The major barriers to reconsideration of the punitive prohibition of cannabis are political, not scientific or legal

There is an increasingly widespread view that international attempts to control cannabis by prohibiting its use have failed and cannot be remedied. Numerous professional associations in medicine, public health, law, and criminology have recognised this failure and the enormous collateral costs of prohibiting cannabis and have recommended consideration of less harmful regulatory alternatives.(13) The Single Convention (1961), the treaty providing the major legal framework for international prohibition of cannabis, states that "a party [government] shall, if in its opinion the prevailing conditions in its country render it the most appropriate means of protecting the public health and welfare, prohibit [the use of cannabis]."(14) Where is the compelling evidence that protection of public health and welfare is "most appropriately" served by the present laws on cannabis? Regulation of cannabis would not breach any nation's international treaty obligations. The major barriers to reconsideration of the punitive prohibition of cannabis are political, not scientific or legal.

The belief that more intensive law enforcement will achieve better public health outcomes represents a triumph of hope over experience

All drugs have risks. Cannabis is not harmless, but adverse health consequences for the vast majority of users are modest, especially when compared with those of alcohol or tobacco. Attempts to restrict availability of cannabis by more intensive law enforcement have been expensive, ineffective, and usually counter productive. The belief that more intensive law enforcement will achieve better public health outcomes represents a triumph of hope over experience. If we discovered that a drug we had been using failed to relieve patients' symptoms and produced unpleasant side effects, would any of us increase the dose?

It is time to acknowledge that the social, economic, and moral costs of cannabis control far exceed the health costs of cannabis use. The search should begin for more effective means to reduce the harms that can result both from cannabis and from our attempts to control it.

- Alex Wodak, Craig Reinarman, Peter Cohen


Competing interests: None declared.


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3.  US Congress, House Ways and Means Committee. Hearings on HR 6385: Taxation of Marijuana. 75th Congress, 1st session, 27 April 1937:91-4.
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14.  Single Convention on Narcotic Drugs. Article 2.5.b. Geneva: United Nations, 1961.


Colin Drummond, reader in addiction psychiatry.

Department of Addictive Behaviour and Psychological Medicine, St George's Hospital Medical School, London SW17 0RE

Proponents of legalisation would have you believe that it is a harmless form of recreational pleasure. It is used mainly by responsible adults and the government has no place in interfering. Penalties for possession and use are disproportionate to the threat posed to the individual user or to society. Very few are harmed by its use: only a reckless minority gives responsible users a bad name by association. Besides, criminalisation fuels rather than prevents an illegal trade and fails to stamp out availability.

The above refers not to cannabis, but to handguns. The United Kingdom's already strict pre-1996 firearms laws did not protect the innocent from the 1996 Dunblane tragedy, though on a wave of popular support from the media the UK government afterwards rapidly almost completely outlawed possession and use of handguns. Now the pro-cannabis legalisation lobby, supported by the same parts of the media that were outraged by Dunblane, seeks to legalise cannabis.

Health risks of cannabis

The pro-cannabis lobby conveniently overlooks the serious health effects of cannabis, pointing to its safety record in comparison with other illicit and legal drugs, such as tobacco and alcohol. The lobby would have us believe that cannabis never killed anyone. It is true that cannabis is relatively safe in overdose compared with heroin, but it is far from harmless in the longer term, particularly for heavy or regular users. The World Health Organization has concluded that cannabis, when smoked, is twice as carcinogenic as tobacco.(1) It causes carcinoma of the lungs, larynx, mouth, and oesophagus as well as other chronic pulmonary diseases,(2) with evidence of a dose-response relation.(3) These carcinomas appear earlier than cancers that are purely the result of tobacco smoking. Cannabis increases the risk of death in people with heart disease.(4) Furthermore, cannabis is now 10 times as pure as it was 20 years ago, which points to potentially greater health risks than earlier research has identified.(5)

In vulnerable individuals, cannabis precipitates schizophrenia and other psychotic disorders and worsens their course. (2, 6) It is worth remembering that about 15% of schizophrenic patients commit suicide. This is not to mention other clear adverse psychological effects of cannabis, including depression, anxiety, and violent behaviour.(6) Cannabis has up to 60 psychoactive ingredients, so it is hardly surprising that it is bad for the mental health of many vulnerable people.

Apart from death, cannabis also causes dependence in about 10% of users and in 50-90% of regular users.(2) The number of cannabis users seeking specialist help has doubled in the past 10 years, accounting for 10% of attendances at drug treatment clinics in the United Kingdom.(7) This is likely to be an under-representation, as most clinics tend to be geared more towards helping users of opiates. Also included among the risks are impairment of cognitive function, reduced academic achievement, teratogenic effects, immunosuppression, impaired fertility, and increased promiscuity and sexually transmitted diseases in regular users. (2, 5, 6, 8) As Henry has recently pointed out "it is perilous for the voice of science to be drowned out by campaigners for legalisation who are dismissive of the mounting evidence on dependence and harm."(9)

The effect of cannabis intoxication on cognitive and motor functions is another aspect of the harm it does. Research on the adverse effects of cannabis in vehicle accidents is complicated by confounding factors such as alcohol intoxication, although in one UK study of fatal road accidents, no alcohol was detected in the bodies of 80% of people found positive for cannabis at necropsy.(10) It is now recognised that the separate effects of alcohol and cannabis on psychomotor impairment and driving performance are approximately additive.(2) And yet because of the absence of a roadside test equivalent to the breathalyser for alcohol, cannabis is much more difficult for the police to detect accurately. All of this points to appreciable social, health, and economic hazards of cannabis.

So called benefits of legalisation

The pro-legalisation lobby claims potential benefits of legalisation in terms of curtailing the black market. But even in Holland, where cannabis has been quasi-decriminalised, some two thirds of the supply of cannabis takes place outside the regulated "coffee shop market."(8) Further, with 1/8 ounce of cannabis costing on average as little as £5 in the United Kingdom,8 it would be difficult if not impossible for a legal, regulated, and taxed market to undercut the illegal drugs pushers. Just the same problems attend the growing illicit trade in "bootleg" alcohol and tobacco imported from mainland Europe to Britain, bypassing any regulation of sale, particularly of sale to vulnerable children.

The pro-cannabis lobby conveniently overlooks the serious health effects of cannabis

Even the much vaunted advantages of cannabis for medical purposes have yet to be proved: so far the evidence suggests that cannabis has more adverse effects than do existing recognised treatments. (11, 12) If it does emerge that cannabinoids are efficacious in certain medical conditions, their licensing as medicines does not require any legal action and is a completely different matter from legalisation of recreational use of cannabis.

In any case, comparison with licit drugs such as tobacco and alcohol hardly provides a model for legalisation. Alcohol claims in excess of 40 000 lives a year in Britain(13) and tobacco some 120 000.(14) No similar estimate is available for cannabis, and no one knows what would be the final toll from its legalisation.

Is deregulation practicable?

The cannabis "industry" is big business, accounting for a reported £4000m turnover a year. The recent share flotation of GM Pharmaceuticals, which manufactures cannabinoids for medical purposes, raised £25m and was six times oversubscribed. With legalisation, it would not be long before the discredited tobacco industry would find new markets for cannabis products. This same tobacco industrywhich is roundly criticised for marketing a killer product and for its lack of ethics and its cynical exploitation of the vulnerability of the addicted public by concealment of the health risksis hounded by the same press that now advocates legalisation of cannabis.

The pro-cannabis lobby would have us believe that a legal cannabis market could be successfully regulated by the UK government, when successive governments have for years failed to act decisively against the tobacco industry and are still failing to deal effectively with the alcohol industry. Two years on, we still await the government's response to Alcohol Concern's proposals for a national alcohol strategy.

The evidence base of the harms caused by cannabis is undoubtedly incomplete and the evidence in some cases is conflicting and confounded, but legalisation of cannabis would, on the basis of what we currently know, lead to increased use and increased harm to public health. As was the case with our old gun laws, no amount of regulation of a legal market would protect vulnerable individuals such as children and mentally ill people.

What we need instead is better public education on the true risks of cannabis and greater availability of treatment for people who are addicted. If there is to be any change in the law in relation to cannabis it should be in terms of the way the law is enforced, including greater consistency throughout the country, and a review of the penalties for possession, rather than any change in the statutes or any departure from international drug conventions. There should be greater emphasis on helping people experiencing problems with cannabis to obtain appropriate treatment.

Perhaps only a minority would be killed or injured by the legalisation of cannabis. But this would be of no comfort to you if your son or daughter was killed by a drug driver or sectioned into psychiatric hospital with a drug induced psychosis. The UK home secretary, David Blunkett, would be well advised to consider more fully the health risks of cannabis before proceeding with his decriminalisation proposal. Reducing police and court time through decriminalisation is likely to be at the expense of public health.Colin Drummond


Competing interests: None declared.


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7.  Runciman R. Drugs and the law: report of the independent inquiry into the Misuse of Drugs Act 1971. London: Police Federation, 1999.
8.  House of Lords Select Committee on Science and Technology. Cannabis: the scientific and medical evidence. London: Stationery Office, 1998.
9.  Henry J. A voice for science in drug debate. Times 2000 Oct 28. (accessed 28 Dec 2001).
10.  Department of Environment Transport and Regions. Report on incidence of drugs in road accident victims: interim results of survey. London: Department of Transport Publications, 1998.
11.  Tramer MR, Carroll D, Campbell FA, Reynolds DJM, Moore RA, McQuay HJ. Cannabinoids for control of chemotherapy induced nausea and vomiting: quantitative systematic review. BMJ 2001; 323: 16-21[Abstract/Full Text].
12.  Campbell FA, Tramer MR, Carroll D, Reynolds DJM, Moore RA, McQuay HJ. Are cannabinoids an effective and safe treatment option in the management of pain? A qualitative systematic review. BMJ 2001; 323: 13-16[Abstract/Full Text].
13.  Royal College of General Practitioners. Alcohol: a balanced view. London: RCGP, 1986.
14.  Raw M, McNiell A, West R. Smoking cessation guidelines for health professionals: a guide to effective smoking cessation interventions for the health care system. Thorax 1998; 53 (suppl 5): S1-38.

© BMJ 2002