5. RESEARCH NEEDS
There is a substantial fund of knowledge about (a) the properties of Cannabis sativa L. and its various psychoactive preparations, (b) the general manner in which those substances are used in different parts of the world, (c) some of the individual and sociocultural factors associated with their use, and (d) the dose-related immediate effects on man of taking cannabis and A9-THC. There are, nevertheless, a number of important questions to be answered with respect to these areas. It is evident also that there are at present many more questions than answers concerning the effects on man of prolonged cannabis use.
In the past few years there has been a major expansion of research activities designed to increase available information about the psychoactive constituents of cannabis, their pharmacological and toxicological effects, and their mode of action (Miller, 1970; Waller, 1970). An acceleration of effort in these areas may be expected as preparations of active principles of known chemical content become increasingly available for studies involving man.
Knowledge resulting from recent research now makes it increasingly feasible and important to undertake a series of studies that can be carried out only in relation to human beings who are taking cannabis or who have taken it for some time. The Group considered it especially important to intensify substantially current research on (a) major epidemiological problems in widely varying sociocultural settings, and (b) the effects on man of using various cannabis preparations in differing amounts for speci-fied, particularly prolonged, periods of time. Research on these problems has so far received less support than is warranted by their importance. In-ternational collaboration would greatly enhance the value of such investi-gations. The following are among the areas of highest priority
5.1 Determination of the cannabinoid content of cannabis preparations in use in different parts of the world
An initial broad study, followed by selective monitoring, is needed for the purposes of comparative epidemiology. It is advisable that a large number of representative samples be collected in each area studied, taking into account the types of preparations and, where possible, their age and source. The minimum information required on the chemical constituents is the A9-THC content. It would be desirable to determine also the content of A9-THC, A9-THC acid, CBN, and CBD.
5.2 Distribution of cannabis consumption in the populations of various countries
This requires attention to the modes and frequency of consumption and the average amount consumed on a given occasion (preferably ex-pressed as A9-THC content). Longitudinal data are also required on the proportion of the population who use and later discontinue use of cannabis and on those who continue to use it sporadically or gradually increase their level and frequency of consumption. The relation of cannabis use to the use of other drugs should be investigated in this connexion. Social and personality factors associated with non-use, as well as with use, in a given sociocultural setting should be studied. Finally, the drugs used by a particular culture for non-medical purposes should be evaluated in order to assess their relative impact on the individual and society. The regions selected for study should represent different levels of acceptance of cannabis use in a variety of sociocultural settings.
5.3 The effects of long-term cannabis use
It would be highly desirable to correlate studies on the effects of long-term use with the distributional picture indicated in section 5.2. That is, samples of users should be selected for special study who are representa-tive of various levels of use as regards quantity and frequency. These samples should be studied with special reference to the occurrence of bronchopulmonary and cardiovascular diseases, chromosomal abnormali-ties, teratogenic effects, organic brain damage, deficits in cognitive and other skills, and social effects such as crime and other deviant behaviour. Evidence of changes in tolerance and characteristic abstinence symptoms and signs should also be sought. Comparisons should be made in all instances with suitable control samples of non-users. Because of methodo-logical limitations, causal relationships often cannot be established. Nevertheless, such studies are useful since they establish the maximum effects that can be attributed to various levels of drug use. For instance, it would be useful to know the maximum effect on a particular variable that could be expected from the daily consumption of 1 g of ganja for 20 years.
5.3.1 The relation of cannabis and psychoses
In section 4.3.2, stress is placed on the need for studies on the prevalence and incidence of various psychiatric disorders in different groups of cannabis users (in relation to level and frequency of use) and in matched controls. In addition, since one of the more frequently mentioned distinguishing features of the " cannabis psychosis " is its relatively short duration as compared to functional psychoses, a prospective study comparing length of hospitalization for psychiatric admissions with and without a history of cannabis use might be useful. Better information on the history of onset is also needed.
5.4 Pharmacological research
Although such research is not the main subject of this section, certain areas are mentioned because of their close connexion with the above topics. Since cannabis is frequently used in combination with other drugs, e.g., tobacco and alcohol, or closely following them, experimental studies of the effects of such combinations are desirable. Further clarification of the relationship of response to dose and to route of administration is needed, from the standpoint both of acute effects and of the development of tolerance. There is also a need to assess further the acute effects of cannabis on attention, judgement, and psychomotor and other skills related to driving or to operating machinery.