Leslie Iversen reviews the case for legalising cannabis for pleasure, while Lord Perry argues that it should be available for medical use
Cannabis has been used medicinally for more than 2,000 years. Queen Victoria used it for menstrual pain. The case for reintroducing cannabis into medicine (it became illegal in 1973) is compelling. Polls suggest that a great majority in this country would support such a move. Last week, people in several United States states joined those in California in voting in favour of allowing cannabis for medical use.
The question of whether smoking cannabis for pleasure should still be illegal is more difficult. Cannabis is the most commonly used illegal drug - 7.5 million people in the United Kingdom have tried the drug, and more than a million are "regular" users.
Each year 70,000 people are arrested for cannabis offences - more than three-quarters of all drug-related crime. Though fewer than half those arrested are prosecuted, more than 30,000 people end up with a criminal record. Is cannabis dangerous enough to justify this?
Looking at the scientific evidence, on the plus side it is clear that taking cannabis is rarely fatal. Lots of people die every year from alcohol and tobacco, but no deaths can be attributed to cannabis.
On the down side, some people do get hooked on cannabis. The drug will dominate their lives. Just how many is hard to determine. If cannabis were a commercial product, more people would use it and the number of those addicted would soar. Not all cannabis "highs" are pleasant, some users experience frightening panic attacks or become temporarily psychotic. Cannabis also impairs driving or flying skills.
Perhaps the most serious health risk is that the drug is smoked - usually mixed with tobacco. Cannabis smoke has all the poisonous tars and carcinogens found in tobacco smoke. Although there is no evidence yet of an increased risk of lung cancer in cannabis users, cancer is a real risk. This is enough to suggest that cannabis use should not be encouraged.
Where does this leave us? The present situation - in which patients using cannabis break the law and in which thousands of young people disregard the law - is unsatisfactory. One could argue that cannabis is no more dangerous than alcohol or tobacco. But alcohol is responsible for more than 100,000 deaths a year in Britain and tobacco smoking for more than quarter of a million.
A "grudging accommodation" with cannabis, without full legalisation, may well be the compromise that is eventually reached.
Leslie Iversen is visiting professor of pharmacology, University of Oxford and specialist adviser to the House of Lords science and technology committee.
For pain relief
This week the House of Lords committee I chair published its report into whether there is a case for relaxing the ban on cannabis for medical or recreational use.
The evidence was varied. No one has died directly from using cannabis, but long-term users became perpetually stoned. Most users started young and gave up by the time they were 30. But there was evidence that many restarted as they got older. Some became psychologically dependent; a few showed withdrawal symptoms.
The committee unanimously agreed that we could see no case for any relaxation of the ban on the recreational use of cannabis.
We also considered evidence that the toxic effects of cannabis are less dangerous than those of many of the drugs currently in use in medicine. The evidence as to whether cannabis benefits patients was more difficult to obtain. The Multiple Sclerosis Society estimates that at least 1 per cent of the 85,000 MS sufferers in the UK use cannabis. They presumably benefit or would not risk prosecution. There have been six clinical trials, in just 41 patients, showing benefit.
The government, the British Medical Association and the MS Society all say that this evidence is inconclusive. For the Medicines Control Agency to license a preparation of cannabis for medical use would require the evidence of clinical trials. We agree, and recommended that such trials be carried out urgently. But we do not contemplate a licence for smoked cannabis, and so we also call for more research to find ways of administering cannabis.
To gain licenses after clinical trials will take five years. We do not believe it humane to deny patients the benefit of cannabis for so long and therefore recommended that the government allow doctors to prescribe unlicensed cannabis by moving it from Schedule 1 to Schedule 2 of the Misuse of Drugs regulations 1985, where it will sit alongside drugs such as heroin and cocaine, both already in doctors' arsenal of drugs.
Lord Perry is chair of the Lords select committee on science and technology.
* Should cannabis be legalised for pleasure or for medical use?
Email us on firstname.lastname@example.org