THE SCIENTIFIC AND MEDICAL EVIDENCE

CHAPTER 1 INTRODUCTION

  1.1     Cannabis has been used medically for thousands of years in oriental and Middle Eastern countries and as an intoxicant for many hundreds of years in India and in the Middle East; and it was employed in Western medicine for at least two millennia. The medical use of cannabis in Europe and North America, however, declined in this century because of the lack of any standardised preparations of the plant product and its unreliable absorption when given by mouth, and because of the development of more potent and reliable drugs for the conditions for which cannabis was then being used.

  1.2     During the 1960s and 1970s there was a large increase in the use of smoked cannabis as an intoxicant in the USA and in Europe, where it had been largely unknown previously as a drug of abuse. The recreational use of cannabis has continued to increase in recent years, particularly among the young. Medical use in the United Kingdom was prohibited in 1973; but cannabis is now the most widely used of all illegal intoxicants.

  1.3     During the 1980s and 1990s there has been renewed interest in the potential medical uses of cannabis and its derivatives. Substantial numbers of patients with various conditions are illegally self­medicating with cannabis and are convinced that they derive medical benefit—although scientific evidence for or against such a conclusion is largely lacking. This has led to calls for cannabis again to be made available for medical applications.

  1.4     In Britain this debate has led a number of expert bodies to review the medical and scientific evidence for and against such proposals. The British Medical Association published a report on the topic in 1997[1]. The Department of Health recently commissioned three literature reviews on cannabis, at the request of the Advisory Council on the Misuse of Drugs (ACMD); we have seen these (they were placed in the Library of the House on 9 June), and the authors have all given evidence to this inquiry[2]. Reports were also published last year by the US National Institutes of Health and the American Medical Association[3].

  1.5     In the light of this heightened interest in cannabis, and particularly the report by the BMA, we decided to examine the scientific and medical evidence to determine whether there was a case for relaxing some of the current restrictions on the medical uses of cannabis. We have also considered whether the continued prohibition of recreational use is justified on the basis of the scientific evidence of adverse effects. Recreational use raises other issues besides the adverse effects of the drug; these are outside our remit "to consider science and technology", belonging instead to the realms of law, sociology and even philosophy, and we have not considered them. Neither have we considered whether cannabis is a stepping stone or gateway to other more dangerous drugs; we have confined our considerations solely to cannabis.

  1.6     Chapters 2 and 3 of this Report are introductory, giving brief accounts of the history of cannabis and its pharmacology. In Chapters 4-7 we review the evidence which we have received on the four key issues: the adverse effects of taking cannabis; current and proposed medical uses; recreational use; and the implications of possible changes to the law. Our conclusions and recommendations are set out in Chapter 8.

  1.7     This report was prepared by Sub-Committee I, whose members are listed in Appendix 1. They received evidence from the persons and organisations listed in Appendix 2, to all of whom we are grateful for their help. We are particularly grateful to the Sub-Committee's Specialist Adviser, Professor Leslie Iversen FRS, Visiting Professor of Pharmacology at the University of Oxford. Professor Iversen attended two international conferences on the Sub-Committee's behalf; his accounts of these appear in Appendices 3 and 4. Abbreviations are listed in Appendix 5.

  1.8     We also acknowledge the assistance of the Parliamentary Office of Science and Technology (POST). POST's report Common Illegal Drugs and their Effects (May 1996), and POST note 113 Cannabis Update (March 1998), have been particularly helpful.

1   Therapeutic uses of cannabis, BMA/Harwood Academic Publishers, 1997, ISBN 90-5702-318-0. Back
2   Cannabis: clinical and pharmacological aspects, by Prof C H Ashton; Psychiatric aspects of cannabis use, by Dr A Johns; Therapeutic aspects of cannabis and cannabinoids, by Dr P Robson. Back
3   NIH Report on the medical uses of marijuana, August 1997; AMA Medical Marijuana, December 1997. Back