INTRODUCTION

This report has been prepared in accordance with the "Marihuana and Health Report Act" (Title V of P.L. 91-296) which requires submission by the Secretary of Health, Education, and Welfare of annual reports to the Congress on the health consequences of marihuana usage. Unlike the preliminary report of September 1970, which more briefly outlined the nature of the research questions currently being posed and the Federal program designed to elicit some of the answers, the present report is designed to summarize the current status of our knowledge of the health consequences of marihuana use. "Health consequences" for the purposes of this document include not only the effects of the drug on the individual's physical and psychological health but also the effects on cannabis use on the society.

As was indicated in the report of September 1970, the health picture with respect to marihuana must at present be regarded as fragmentary and clearly incomplete. Many of the most important questions regarding the implications of long-term, chronic use will require significant periods of time to answer. Extrapolation from data based on cultures in many respects significantly different from our own is inevitably hazardous. The picture is further complicated by the degree to which drugs as actually used in a given society differ from pure laboratory chemicals. Thus, we are forced to rely on lines of evidence each in itself admittedly incomplete but which taken together will ultimately converge toward reliable and valid conclusions regarding marihuana and health.

SOURCES OF INFORMATION

A wide variety of sources of information have been used in preparing this report. Careful consideration has been given to the convergence of evidence to support a particular finding; or, in the absence of this, the confidence placed in the statement has been accordingly reduced. It should be noted that the information upon which this report is based includes both published and unpublished reports from grantees of the National Institute of Mental Health and investigators who were supplied with quantities of marihuana (in various forms and potencies), and who, in turn, have shared the results of their research with us.

Published results of surveys, studies and experiments from many scientific sources have been carefully reviewed. Selected articles from journals, newspaper articles of high quality, government reports concerning marihuana use in other countries, ranging from the Indian Hemp Commission of the last century to the recent Le DaM Commission of Canada, have also been used and provide a picture of marihuana use in other regions of the new and old world. Reports of consultants, as well as the proceedings of various symposia and conferences, have been studied.

It is important to recognize that any one source of information is inevitably subject to limitations inherent in the research design. Thus, no single study can be regarded as definitive. Conclusions that are drawn or persistent uncertainties are a function of the information available at any given point in time. Final judgments, given our present limitation of knowledge, are not possible at this time. A balanced objective analysis of the health implications of marihuana must consist of a series of successive approximations as our information becomes increasingly complete.

In order to be of value to the more scientifically sophisticated reader, some portions of this report are inevitably technical. Wherever these technical portions have lent themselves readily to translation into more widely understood language, this has been done. In some portions, notably those on the chemical characteristics of natural and synthetic materials, in which such a translation is neither readily possible nor essential to a general understanding of the report, no such attempt has been made. In this way it is hoped that the report will meet both the needs of the general reader and to some extent those of the technically sophisticated as well.