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1.1 Terms of reference

Your Sub-Committee has invited evidence on the medical use of cannabis and its derivatives. In this report we have attempted to respond to some of your specific questions with data from our own research, and in some cases reviews of the relevant literature where this has been gathered, (where I.D.M.U. evidence has been provided for legal cases involving medical uses). Some references are given which were not in the BMA report on Therapeutic Uses of Cannabis (November 1997) - chiefly on traditional medical uses and other studies conducted prior to 1970. There are also other sources which may not have been previously brought to your attention. These reviews are not comprehensive, and do not cover important areas including multiple sclerosis, use as antiemetic/appetite stimulant e.g. in cancer chemotherapy and HIV, or reduction of intraocular pressure in glaucoma sufferers.

In order to reply coherently, we have begun with background information, based on our research and others", which gives the context in which your specific questions can be addressed. This is in: Section 1: Types of cannabis available, Section 2: Methods of use, Section 3: Consumption patterns of regular users, and Tables 1: Amounts smoked per day and 2: Cannabis use levels (percentiles).

Other areas which are relevant though not specifically requested are:

Section 7: Medical use in California

Briefly describes a recent social experiment in making cannabis widely available for medical purposes, with popular support, legal and medical controls on misuse, and a nascent system for production and distribution. Whatever the scientific or other evidence on which they based their vote, Californians devised a system which supports medical uses while maintaining prohibition on recreational use.

Section 8: Treatment of "medicinal" cannabis users by the UK criminal justice system:

Your Lordships expressed an interest in this matter in a recent session. Data from our research, court experiences, and other sources.

Table 6: Outcomes of criminal prosecutions reported among medicinal users

Table 7: I.D.M.U. Medicinal Cannabis Cases


1.2 Specific Questions posed by the Committee

What are the physiological effects (immediate, long-term and cumulative), of taking cannabis, in its various forms?

What are the psychological effects?

Section 5: Effects of cannabis - effects of duration, dependence?, on driving.

Section 5.4: Health problems and benefits attributed to cannabis use.

Table 3: Reported health problems attributed to cannabis use.

Table 4: Reported health benefits attributed to cannabis use.

Table 5: Reasons for using cannabis.

Responses from our surveys of regular cannabis users - total 2794 respondents. Overwhelmingly the most common positive psychological effect reported by regular users is relaxation/stress relief, followed by mood elevation and increased sociability or personal development. Negative effects most commonly reported include memory problems, paranoia/anxiety, amotivation and respiratory problems. Significant associations between respondents reporting problems, levels of use, and related variables including duration of use, other drug use, spending, subjective ratings of drugs, methods of use etc. are summarised in the tables. The most common "beneficial" physical effects are on pain relief and respiratory benefits, such as reduced asthma and drying of mucosae during colds and flu.

How do these effects vary with particular methods of preparation and administration?

Section 4: Methods of Ingestion. In our studies, an estimated 96.2% of cannabis use is by smoking, usually with tobacco, although 25% of respondents eat or drink it on occasions. Also, a small US study comparing the harmfulness of smoking methods is reviewed.

Smoked cannabis poses clear risks to physical health, as would smoking any substance, although this represents a rapid and controllable route of administration. The effects of oral cannabis preparations vary considerably, with a risk of overdose due to the slow onset of action. Many medicinal users report the effects of smoked cannabis to be more beneficial than oral cannabinoids, and it is possible that modulation of the effects of THC by "minor" cannabinoids may reduce some of the unwanted side-effects or potentiate the therapeutic effect.

Our research provides the most comprehensive studies currently available of the dosages of cannabis/cannabinoids and methods of use among large samples of short and long-term cannabis users in the UK.

To what extent is cannabis addictive?

To what extent do users develop tolerance to cannabis?

Section 5.1: Effects of duration of use.

Table 2: Effects of duration of use on patterns of use.

A substantial proportion of users continue into middle age, and a greater proportion use the drug daily than with other controlled drugs. After approx. 2 years experimental and heavy use, average monthly use declines with age. The pattern of cannabis use among regular/long-term users is comparable to that of caffeine, with the average regular user consuming the drug on around 5-6 occasions per day.

What is the evidence that cannabis in its various forms has valuable medicinal actions?

In the treatment of which diseases?

How rigorous is the evidence?

Section 6: Medical uses of cannabis. Raw material vs. cannabinoid compounds. Literature reviews on historical uses, pain relief, anti-convulsant, stress and depression, asthma relief, opiate/ alcohol dependence.

Table 4: Reported health benefits attributed to cannabis use.

There is strong evidence that cannabinoids may be of benefit in the management of pain and spasticity in conditions such as spinal injury, arthritis and multiple sclerosis. Cannabinoids (Nabilone/Dronabinol) have been approved for medical use in treating the side-effects of cancer chemotherapy, as antiemetics and appetite stimulants. There is convincing evidence of bronchodilator activity, although smoking as a route of administration would not be a preferred route for asthmatics. There is conflicting evidence of the efficacy of cannabinoids in the treatment of glaucoma, epilepsy (particularly cannabidiol), and addiction to opiates and alcohol. Anecdotal evidence of anti-anxiety activity runs counter to the little scientific evidence available, although this may be attributable to differences in the effect of cannabis on na"ve and experienced users.

1.3 General questions of the Committee - A Case for Change?

Is there a case for promoting clinical trials even if the current level of control is maintained?

Yes. There is substantial anecdotal evidence of health benefits from cannabis, and from some cannabinoids. Recent work on cannabinoid receptors suggests new lines of enquiry and provides a theoretical basis for several commonly-reported conditions. The Misuse of Drugs Act and other regulations were intended to permit research, but the present licensing system and policy has severely limited research opportunities, and should be reviewed. There is an urgent need for fundamental research and/or clinical trials for a variety of conditions. The risks of morbidity and mortality attributed to cannabinoids are surprisingly low, particularly in comparison to existing medications such as opiates, non-steroidal analgesics and benzodiazepines.

New research is now being published at an increasing rate, recent publications have indicated therapeutic potential of CBD as an antioxidant in the management of strokes, and reduction of tumours in breast cancer from anandamide, and also shown that cannabinoid receptors in the skin are activated by traumatic injury. On the other hand, researchers have also reported gene mutation from cannabis smoke, and a review of cognitive effects in long term users concluded that cannabis may interfere with the "filter" system used by the brain to keep out unwanted or irrelevant information. Clearly the field of "therapeutic" cannabis and cannabinoid research is advancing rapidly, with economic implications from the development of a new class of drugs. Should the UK maintain the hitherto strict regulatory regime, the opportunities for the British pharmaceutical industry to benefit from new product development could damage our international competitiveness.

How strong is the scientific evidence in favour of permitting medical use?

In some cases cannabis products may be more effective than other treatments. It would seem inhumane to completely block legal access to a substance which makes sick people feel better, when no better alternative is available, even if any beneficial effects were of unknown aetiology or of undetermined efficacy. Where the drug is of demonstrable benefit and alternative treatments are less effective or carry greater risks, a continued refusal to permit medicinal use, due to perceived risks of a change in public attitudes, appears unjustifiable both on moral and on public health grounds.

How strong is the scientific evidence in favour of maintaining prohibition of recreational use?

Some commentators would seriously argue that legalising the recreational use of cannabis would lead to a breakdown of society, others would counter that cannabis/hemp could "save the world". In our view, both these positions are equally erroneous.

The potential harmful effects of cannabis have, over the past century, been investigated far more thoroughly than potential benefits, with generally negative results. The main physical dangers associated with cannabis arise from smoking it, particularly mixed with tobacco in unfiltered cigarettes, leading to respiratory or cardiovascular problems. Psychological risks include anxiety/panic/paranoia attacks mainly among na"ve users, and a risk of psychosis in a small number of predisposed individuals. Even if the worst plausible dangers were all proved, using cannabis would pose a lesser risk to health than many common sports, other recreational activities, legal drugs or products such as alcohol, tobacco, caffeine, sugar or saturated fats.

Governmental and medical reports, from several countries including the UK, have suggested that the harmful effects of a prohibition policy, on individuals and society, may be greater than the harmful effects of the drug. Prohibition, particularly the effects of arrest, may reinforce rather than deter drug use by reducing the options for full participation in society, including lost opportunities for employment, housing, foreign travel and to the users driving license as a result of a criminal record or positive urine sample.

Prohibition has created a confrontational atmosphere which stifles open debate and dissemination of information as to the real risks of using different drugs, and creates an incentive to experiment among teenagers keen to rebel against the strictures of their elders. A forbidden fruit, when no longer forbidden, loses much of its sweetness. Experience in the Netherlands and elsewhere does not suggest that a relaxation in the law leads to an increase of use over the longer term, and rates of drug use, including problem indicators, in Holland are lower than in the UK.

Scientific evidence is only one of a number of considerations which apply in formulating drug policy; public moral and political attitudes and international treaty obligations appear to take precedence over rational consideration of such evidence. Any decision as to the desirability and nature of law reform would need to take account of matters beyond the scope of this committee, including prevalence of use, effects on crime/driving, economic effects both direct (enforcement expenditure, tax revenues) and indirect (effect on manufacturing industry and employment of reduced acquisitive crime), international relations (including drug tourism) and social attitudes, as well as public health considerations and the proper constitutional role of the state in the control of individual behaviour.

The nature of any change in the law is critical, whether this involves an increase or reduction in penalties, rescheduling to Class C (de facto decriminalisation of possession), and/or the means of achieving a legitimate method of supply in a legalised market (e.g. taxation/regulation, licensing, coffee-shops, clubs or free-market solutions). Each of these options would create advantages and disadvantages which must be carefully weighed before any policy is adopted.

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