Cannabis

I have discussed drug dependence in some detail in order to give an idea of the range of phenomena covered by this term. Thus, to say that one may become dependent on marihuana is to say very little. As noted above, marihuana use does not result in the development of physical dependence or tolerance. Reaction to the drug is extremely variable, ranging from aversion (an unpleasant experience is likely to be followed by a disinclination to take more), to "moderate to strong psychic dependence." (Who) Reports in the literature indicate that, in the 'West' at least, use of marihuana is mainly periodic—partly owing to supply considerations—and that users have little difficulty in giving up taking the drug (e.g. Becker, Murphy.) Termination of the habit or indefinite suspension of it seems to be generally easier than for tobacco smoking, and 'compulsive' use is relatively rare. Experimental subjects and naive users are frequently not interested in further use.

The general term 'cannabis' covers the two main forms of the drug preparations: marihuana—the flowering tops, leaves, stems and seeds of the female plant, and hashish—the resin exuded by the flowering tops, leaves and stems. The active constituent is contained in the resin (the concentrated resinous extract thus being the more potent form). Recent studies have shown that a particular substance. 9 (or 1-)transtetrahydrocannahinol (THC), isolated from hashish and shown to be present in marihuana, has the characteristic marihuana-like activity in man. ('marihuana' is often used to include hashish. This usage will be followed here, except where dosage considerations become important. It is now possible to measure dosage as quantities of THC, but this is a comparatively recent development.)

Most marihuana is smoked, although it is occasionally taken orally. Isbell et al. showed that a given quantity of THC is 2-3 times more potent when smoked than when taken orally (calculated from changes in peak pulse rate, and from questionnaire responses for 10 subjects). They comment that the reasons for this "are unknown but might include more rapid absorption, less detoxification because of not passing through the liver via the portal veins and possible conversion of 9-THC to a more active substance by heat."

Before discussing the specific effects of marihuana, it is necessary to point out that users have, on the whole, to learn to recognise and appreciate the effects in order to obtain the desired 'high', (e.g. see Becker,) Naive users may not realise they have actually had a marihuana reaction, (and consequently will not in fact have been 'high'.) A typical response is described by Zinberg and Weil: "One of the naive subjects [who did not know what he had taken] summed up the unimpressiveness of his subjective reaction by saying 'I have probably had something but it can't he marihuana because I would he much more stoned than this.' "This was after smoking two marihuana cigarettes containing perhaps 2g of finely chopped leaves. None of the 9 naive subjects became subjectively high.

However, the more convivial atmosphere of Ames' experimental arrangements enabled his naive subjects to get some son of 'high'. His subjects were encouraged to report on every change they felt, and were anxious to do so. They were also in the presence of the other subjects throughout the experiment, and were thus able to observe the effect of the drug on others, to compare this with their own feelings, and to a certain extent 'share' the experience. Zindberg and Weil's subjects were effectively in isolation, however, with a minimum of personal contact with the experimental staff. This arrangement had the result that the naive users did not experience any 'high', though — as would be expected —it did not prevent the regular users from having one.

Howard Becker found that some regular users lost the facility to get good 'highs'. After stopping for a while, smoking was continued and the differences once again were perceived and appreciated.