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. 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
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