Legalise cannabis?

When the House of Lords advocated the legalisation of cannabis for medicinal purposes, the Government reacted swiftly to rule out the possibility.

George Howarth, a minister at the Home Office, said, "The safety of patients is our priority, and the Government would not allow prescription of any drug which had not been tested for safety, efficacy and quality through that clinical process." He added that it supported further trials into the benefits of cannabis for MS (multiple sclerosis) and chronic pain.

Whilst the Lords' science and technology committee agreed that the present ban on the recreational use of the drug should not be removed, Lord Perry of Walton, its chairman, said that clinical trials could take up to five years, too long for sufferers to wait. "We felt that the evidence of benefit to these patients with very distressing symptoms was such that we shouldn't make them wait that long," he said, adding that the benefits of the drug had already been proven in some tests on animals.

Lord Perry suggested that cannabis should be moved from the list of "schedule one" drugs, which are illegal to use even if they relieve pain, to "schedule two", from which doctors may prescribe to named patients. Although the Lords' recommendation was welcomed by patients' groups, politicians, and some anti-drug campaigners, the British Medical Association said that making cannabis available on prescription would be a misguided move with the possibility of preventing new, more effective drugs being developed.

In The Lancet which appeared a few days after these exchanges, an article by Professor Wayne Hall and Dr Nadia Solowij, of the National Drug and Alcohol Research Centre at the University of Sydney, set out what appear to be the most likely adverse effects of smoking cannabis. The evidence summarised by Hall and Solowij was considered by the science and technology committee of the House of Lords in reaching their conclusion. Three years ago The Lancet's editorial stated: "The smoking of cannabis, even long term, is not harmful to health" (11th November, 1995). Needless to say, the legalise-cannabis lobby made capital out of the statement. With hindsight, the leader writer now reflects that perhaps they should have "begun...with a less provocative statement." Nonetheless, he goes on to say that "it would be reasonable to judge cannabis less of a threat to health than alcohol or tobacco, products that it many countries are not only tolerated and advertised but are also a useful source of tax revenue. The desire to take mood-altering substances is an enduring feature of human societies worldwide and even the most draconian legislation has failed to extinguish this desire. For every substance banned another will be discovered, and all are likely to have some ill-effect on health. This should be borne in mind by social legislators who, disapproving of other people's indulgences, seek to make them illegal. Such legislation does not get rid of the problem; it merely shifts it elsewhere."

Professor Hall and Dr Solowij provide a summary of adverse effects of cannabis intended as a guide to doctors who need to advise patients on the drug's use:

The Lancet concludes that it should qualify its opinion of three years ago "and say that, on the medical evidence available, moderate indulgence in cannabis has little ill-effect on health, and that decisions to ban or to legalise cannabis should be based on other considerations."

Acute effects

  • Anxiety and panic, especially in naïve users.

  • Impaired attention, memory, and psychomotor performance while intoxicated.

  • Possibly an increased risk of accident if a person drives a motor vehicle while intoxicated with cannabis, especially if cannabis is used with alcohol.

  • Increased risk of psychotic symptoms among those who are vulnerable because of personal or family history of psychosis.

Chronic effects (uncertain but most probable)

  • Chronic bronchitis and histopathological changes that may be precursors to the development of malignant disease.

  • A cannabis dependence syndrome characterised by an inability to abstain from or to control cannabis use.

  • Subtle impairments of attention and memory that persist while the user remains chronically intoxicated, and that may or may not be reversible after prolonged abstinence.

Possible adverse effects (to be confirmed)

  • Increased risk of cancers of the oral cavity, pharynx, and oesophagus; leukaemia among offspring exposed in utero.

  • Impaired educational attainment in adolescents and underachievement in adults in occupations requiring high-level cognitive skills.

Groups at higher risk of experiencing these adverse effects

  • Adolescents with a history of poor school performance, who initiate cannabis use in the early teens, are at increased risk of using other illicit drugs and of becoming dependent on cannabis.

  • Women who continue to smoke cannabis during pregnancy may increase their risk of having a low-birthweight baby.

  • People with asthma, bronchitis, emphy-sema, schizophrenia, and alcohol and other drug dependence, whose illnesses may be exacerbated by cannabis use.