CANNABIS: 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.

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.

3 NIH Report on the medical uses of marijuana, August 1997; AMA Medical
Marijuana, December 1997.