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Salient: Victoria University of Wellington Students' Newspaper. Vol. 32, No. 10. 1969.

Pot — A Scientif Inquiry

page 6


A Scientif Inquiry

John Woolf Claudia Tattersfield

"facts ... that only fail to surprise and shock me now as much as they ought because they are so familiar: the relative harmlessness of cannabis and its illegality." Alistair MacIntyre. New Society. Dec. 5, 1968.

"sooner or later pot smoking will be legalised in Britain." Editorial. New Society. Dec. 5, 1968.

"Marihuana in itself is relatively harmless. The effect of taking it to excess is much less drastic than is the effect of taking alcohol." Editorial. The Dominion. Jan. 10, 1969.

The above quotations illustrate the current interest in marihuana, the increasingly widespread belief in its 'relative harmlessness', and the development of a more permissive attitude towards its use. John Lennon, Peter Sellers and Mick Jagger, amongst other celebrities, are apparently enjoying, or have enjoyed, smoking pot. The publicity given to these activities, and the favourable reports that cabinet ministers and M.P.'s. at least in Britain, may be getting from their children and grandchildren, will all facilitate general acceptance.

In this article I will say something about drug dependence generally, and will then discuss the effects of marihuana specifically—both the immediate short term reactions, and the longer term, less clearly defined effects.

Dependence Not "Addiction"

'Drug addiction', with its lurid connotations and loose, non-medical use, has been rejected as a term with which to describe drug habits. The World Health Organisation has developed over recent years the notion of 'drug dependence' in an attempt to find "a term that will cover all kinds of drug abuse", that is, "excessive or persistent use beyond medical need." (Bull Who. 1965.) "Drug dependence is a state of physic or physical dependence, or both, on a drug, arising in a person following administration of that drug on a periodic or continuous basis. The characteristics of such a state will vary with the agent involved, and these characteristics must always be made clear by designating the particular type of drug dependence in each specific case; for example, drug dependence of morphine type, of barbiturate type, of amphetamine type etc. The specification of the type of dependence is essential and should form an integral part of the new terminology, since it is neither possible nor even desirable to delineate or define the term drug dependence independently of the agent involved .... It must be emphasised that drug dependence is a general term that has been selected for its applicability to all types of drug abuse and thus carries no connotations of the degree of risk to public health or need for any or a particular type of drug control."

Psychic dependence is "a particular state of mind ... [where] there is a feeling of satisfaction and a psychic drive that require periodic or continuous administration of the drug to produce pleasure or to avoid discomfort". Physical dependence is "an adaptive state that manifests itself by intense physical disturbances when the administration of the drug is suspended or when its action is affected by the administration of a specific antagonist. These disturbances, i.e. the withdrawal of abstinence syndromes ... are characteristic for each drug type." Drugs may also induce tolerance, which is "an adaptive state characterised by diminished response to the same quantity of drug or by the fact that a larger dose is required to produce the same degree of pharmacodynamic effect."

Some drugs which lead to psychic dependence also lead to physical dependence and/or tolerance. Psychic dependence, physical dependence and tolerance all develop with continued use of drugs such as morphine, heroin, alcohol and barbiturates, (all depressants). Psychic dependence and tolerance develop with use of amphetamines and LSD. (stimulants), although with the latter, tolerance disappears as rapidly as it develops—in a few days. Marihuana and cocaine (stimulants), are associated with psychic dependence only, cocaine use typically leading to greater dependence. Fatigue or mild depression may follow a drug experience without being associated with any 'abstinence syndrome' proper.

'Drug dependence' thus takes some account of the range of different drug reactions and it has no connotations of risk or control. However, it is important to note that the definition of 'drug dependence' given by Who is not a simple medical one. Various value judgements are implicit. Most obviously, Who still insists on talking about drug "abuse" (i.e. non-medical or non-scientific use), and does not consider for example, recreational use as something separate. That is except, somewhat inconsistently, in the characterisation of drug dependence of the alcohol type. They state that this "may be said to exist when the consumption of alcohol by an individual exceeds the limits that are accepted by his culture, if he consumes alcohol at times that are deemed inappropriate within that culture, or if his intake of alcohol becomes so great as to injure his health or impair his social relationships." Psychic dependence is said to occur, however, "in the mildest grade [where] alcohol is missed or desired if not available at meals or at social functions", which, of course, can occur well within cultural norms. Or perhaps Who is suggesting that psychic dependence in the case of alcohol does not constitute a 'drug dependence of the alcohol type'.

'Tolerance' and 'physical dependence' are relatively unproblematical: they can be shown to exist more or less unambiguously by a series of experiments, either with animals or with humans.

'Psychic dependence' is not so simple. It is generally agreed that it may be present in varying degrees. It is recognised that it is a very common, widespread phenomenon. One may be psychically dependent on TV watching, eating cornflakes (or just eating), cunnilinctus, playing rugby, listening to the Beatles or to Baroque music, protesting, reading, wearing trousers, cigarette smoking, church going, etc. None of these dependency activities are regarded as particularly reprehensible within cultural limits, and the participants are not generally subject to prosecution. Many activities may form the basis of a 'compulsion', and it is often rather difficult to decide whether one exists. Personal values may become involved very quickly in deciding in any individual case.

In other words, as indicated above, the mere fact of psychic dependence has no implications for risk or control. It merely refers to the fact that there is a greater likelihood of a person repeating an action if previously it has resulted in a pleasurable experience or in the removal of discomfort.


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.

Length Of Reaction

The effects of marihuana can be detected within about 15 minutes after smoking (deep inhalations and maintaining inspirations). The peak reaction occurs about half an hour or so after smoking. Some effects may be noticeable several hours later, depending on the dose. Zinberg and Weil found that for doses of 0.5 or 2g (leaves), "observable effects ... were largely dissipated by three hours after the end of smoking." The length of the marihuana experience tends to vary with the individual and the dose. If the drug is eaten rather than smoked, the onset of symptoms occurs later, and the experience may be consiberably longer, (absorption into the bloodstream takes much longer).

The most consistently appearing physical effects are an increased or unstable pulse rate, and suffusion of the conjunctiva, (reddening due to dilatation of the blood vessels). Blood pressure, respiratory rate, pupillary size and threshold for elicitation of the knee jerk are more or less unaffected. Blood sugar levels, possible changes in which were previously thought to be associated with reported effects of hunger, are in fact unchanged. Other reported effects are dryness of the mouth, diuresis, numbness or coldness of the extremities. Some sleepiness, nausea or headache may also occur. (See experimental reports of Isbell el al., Ames, Zinberg and Weil. The doses used were equivalent to about 2g of marihuana leaves smoked.)

A number of workers have studied the effects of marihuana on various performance tests. Some early experiments are recorded in the 'Report of the Mayor's Committee on Marihuana' (New York 1944), cited by Edwards, and by Clark and Nakashima. These suggested that simple functioning, such as reaction time and tapping, are not impaired except by large doses. However, more complex psychomotor functions may, they state, show impairment at comparatively low doses.

More recently, working with naive subjects on doses equivalent to 1.5-4g crude marihuana, Clark and Nakashina conclude that effects on "complex (choice) reaction time and on a digit code memory task were most consistently impaired", though there were still marked individual differences. One problem, noted here and elsewhere, isoccasioned by the frequent waxing and waning nature of the experience, which results in varying impairment on the same dose.

Zindberg and Weil's investigation demonstrates the important differences between the reactions of naive and regular users. Three tests were used. The first was a continuous performance test lasting five minutes, in which the subject had to press a button whenever a particular letter appeared in a sequence of letters being flashed across a screen. The test was repeated with a strobe light flickering at 50 cycles per second. Normal subjects make few errors on this test, but it has been found that lack of sleep and some drugs can adversely affect performance on it. The second test was a digit symbol substitution test, a simple test of cognitive function-page 7ing which required the subject to match symbols to numbers. The third test was a 'pursuit rotor' test, measuring muscular co-ordination and attention; it involved keeping a stylus in contact with a small spot on a moving turntable.

There was no significant change for either group on the first test, with or without the flickering strobe light. On both the digit symbol and pursuit rotor tests the performance was good, actually improved on these tests after smoking marihuana.

Estimations of time intervals are often inaccurate after smoking marihuana, there being a strong tendency to estimate the time as being much later than it is, and a feeling that events are taking much longer than they really are.

Immediate recall may also be impaired. Ames, using naive subjects, notes that conversations became bizarrely disconnected because of this. However, if reminded of a previous statement, the subject could pick up the thread again. Direct questioning invariably elicited prompt and relevant replies, but if the subjects were left to themselves to pursue a train of thought, the difficulty of immediate recall manifested itself. One of Zinberg and Weil's naive subjects, after 2g of marihuana, commented "I would keep forgetting what I was doing, especially on the continuous performance test, but somehow, every time an 'x', [the critical letter] came up, I found myself pushing the button."

Some of the gaps in existing experimental work are obvious. Few subjects are being used; they are generally all young (20-30), and tend to be members of rare groups—students, prison inmates, ex-opiate addicts', regular marihuana users etc. Only some effects e.g. suffusion of the conjunctiva after moderate doses, could be expected to be uniformly present in the reactions of subjects taken from many diverse groups.

A greater range of tests need to be carried out with a wider range of doses. It seems likely, however, that the usual amount smoked recreationally is comparable to the above experimental doses. The Chopras found that in their Indian sample, heavy users rarely smoke more than 10g a day of ganja (flowering tops and resinous stems from female plant). (cited by Murphy.) Heavy users in the States use similar amounts, perhaps 5-10 marihuana cigarettes a day. Most marihuana smoked, however, is taken on a more casual basis and the quantities are correspondingly smaller. (The amount of hashish reportedly taken by heavy users in e.g. India and N. Africa, would result in doses of perhaps 5-10 times more THC than would be taken in by heavy marihuana smokers in the West.)

The range of tests, and the circumstances under which they are conducted, are more serious limitations on making evaluations for practical situations. Is it safe, for example, to drive a car two hours after smoking, say three or four joints? The evidence suggests that the results might not be disastrous, but obviously care and some control must be exercised (as for alcohol and other drugs). More complicated tasks, less contingent on the laboratory setting, should be investigated. Many users claim that the effects of marihuana are more easily suppressed than are those of alcohol. (see e.g. Becker, Zinberg and Weil.) It is important to know at what level of complexity, effective task performance becomes impaired. Variations in performance with different levels and duration of use should be further investigated.

Subjective Experience

Mood alteration tends to be in the direction of euphoria, and hilarity, apparently occasioned by practically nothing, is common. Inappropriateness of affect is frequently exhibited, and some degree of delusional thinking may lead the user to become apparently exaggeratedly or unwarrantedly suspicious. For example, he may start to worry about hidden listeners, concealed implications of questions, people's motives, and may even become unduly worried that the vice squad might be about. This may to a certain extent be the result of greater perceptual acuity; if an individual is more aware than usual, of a person some distance away, he might infer that the person has some special interest in him, and approaching footsteps in a corridor might sound unnaturally loud, the sinister implications being obvious.

A certain amount of depersonalisation may be experienced. (e.g. The user may feel as though he is observing himself rather as if he is an actor in a film he is watching.) Some aspects of the experience may be sufficiently unusual as to be disturbing, and may lead to mild anxiety, especially in the case of a naive user. There may also be a certain amount of depression or fatigue as the effects of the drug are wearing off.

Marihuana tends to result in increased passivity. Users are less inclined to engage in activities than to be spectators, (except, perhaps, from the more traditional ones such as making love, or playing jazz.) Inhibitions may be lessened to some extent, but this (as many of the effects) is very dependent on the immediate setting, and there is a continuity with the non-drugged personality and behaviour of the person concerned.

Disturbances in thought processes may be experienced, such as difficulty in immediate recall, multiplication of associations, disconnected thought sequences, and time perception may be altered. Reality contact is never totally relinquished it seems, and though users sometimes seem to be 'far away'. Ames found that they can still be stimulated to respond appropriately and directly to questions and other external stimuli.

True hallucinations appear to be rare, though vivid images when the eyes are closed may be 'seen', and visual and auditory distortions and illusions are common. Changes in perspective, and greater intensity and duration of after-images may be experienced. The user may become more aware and more fascinated by his own body, as well as by external stimuli, especially works of art. Intensification of bodily sensations may result in some exceptionally pleasurable sexual experience, but it may be that there is an unusual lack of interest in sexual activity.

There appear to be few long term physical effects of marihuana use, and none have been demonstrated in the West. An early Indian study (Chopras, 1939, cited by Murphy, and McGlothlin and West.) indicates that conjunctivitis may follow heavy prolonged use, and possibly bronchitis, although Murphy comments that this "is presumably due to the crude smoked material as much as to the specific drugs." 'Asthma has also been suggested. However this condition is partly psychosomatic and the Chopras themselves do not believe it is a consequence of marihuana smoking.)

There appear to be few long term physical effects of marihuana use, and none have been demonstrated in the West. An early Indian study (by the Chopras in 1939, cited by Murphy and by McGlothlin and West) indicates that conjunctivitis may follow heavy and prolonged use, and possibly bronchitis, although Murphy comments that this "is presumably due to the crude smoked material as much as to the specific drugs." (Asthma has also been suggested. However, this condition is partly psychosomatic, and the Chopras themselves did not believe that it is a consequence of marihuana smoking.)

Some potentially unpleasant psychological reactions have been mentioned. Many experiences especially novel or unexpected ones, may become the basis for anxiety. Bad reactions are generally transient or are dealt with by supportive friends, and rarely lead to psychiatric treatment. An experienced user said of a novice who had become frightened by a particularly marked effect, "She's dragged because she's high like that. I'd give anything to get that high myself. I haven't been that high for years." (Quoted by Becker.)

Recently Keeler (1967) has reported 11 cases of 'adverse reactions' to marihuana from amongst student or former student users These included anxiety and panic reactions, depression, confusion and disorientation, depersonalisation, and paranoid phenomena during the drug reaction. Disregarding the problems of giving satisfactory clinical definitions of 'adverse reaction', we can at least note that these are not well-defined clinical syndromes. Two, (disorientation and depersonalisation), have in fact been defined by other users as pleasurable. And all but two of the eleven persons interviewed considered that the benefits of cannabis by far outweighed the negative aspects, and intended to continue use of the drug. These reactions were all temporary, and do not seem to have been particularly severe.

Murphy has summarised much of the (international) evidence pertaining to marihuana and serious mental illness. The problem of the 'marihuana psychoses' was one that worried early investigators. However, as far back as 1942, Allentuck and Bowman state that "a characteristic cannabis psychoses does not exist. Marihuana will not produce a psychosis de nova in a well-integrated, stable person." (cited by Murphy.) More recent work has tended to confirm this general impression. Murphy concluded that, as far as it is possible to estimate, the incidence of major mental disorders among marihuana users is not greater than in the general population.

Becker has pointed out that concern over a drug must be seen in a cultural context. It is most pronounced when the drug is new (whether or not there is actually any danger). Marihuana was first used to any extent in the U.S. around the 1920's and 30's, and there were a number of reports about this time on marihuana induced psychoses. The reports declined in number in the 30's, and Becker found none indexed in Psychological Abstracts or the cumulative Index Medicus after 1940, (Reported in Trans-Action, March 1968, pp7-8.)

In assessing reports of 'bad' reactions, it must be remembered that the population of users may be very large, so that individual 'risk' cannot be determined with any certainty, though it would appear to be very slight. A drug reaction depends very much on the personality of the user and the setting, as well as on the drug itself. The contributions of the first two factors must be adequately controlled if the specific contribution of the drug is to be assessed. A person who is given to anxiety or hallucinations, for example, is probably more likely to experience a bad reaction. (It has been claimed occasionally that the mentally unstable are disproportionately attracted to marihuana. It is to be expected that such people would cope less ably with a disturbingly novel experience.) Furthermore many drug users are multiple drug users. In such cases it is impossible to assign to the action of a particular drug, a disturbance which is not concurrent with, or immediately subsequent to, the use of that drug.

Briefly, one must consider the history of the individual concerned before marihuana use, before the bad reaction, and after it. It must be decided just what personality changes, if any, have occurred, and just what constitutes a 'bad' reaction. In any case it must be remembered that there appear surprisingly few reports of adverse reactions in literature, and those that do appear almost invariably involve merely temporary disturbances, generally limited to the few hours of the pharmacological drug reaction itself, and rarely require hospitalisation.


Marihuana, then, is a relatively harmless, 'soft' drug. Continued use does not lead to the development of tolerance, physical dependence or serious tissue pathology, (cf. alcoholism and the sequelae: cirrhosis, gastritis, brain damage.) Psychic dependence may be present in varying degrees and only infrequently reaches the level of a compulsion: most users can terminate the habit with little difficulty; and much use is casual or periodic.

The effects of marihuana show a wide variation with situation, the individual personality of the user and the dose. Increased pulse rate and suffusion of the conjunctiva appear to be among the few physical changes universally present.

Performance on some simple psychomotor tasks is unimpaired. Other tests, such as digit symbol substitution and pursuit rotor, show impairment for naive users but improvement for regular users. Performance on more complex psychomotor tasks suffers for all users.

Marihuana smoking results in a diverse range of psychological reactions, although the experience of naive users may be minimal and they may not get 'high'. There is generally good reality contact, and the effects of the drug can be suppressed to some extent. Unpleasant (or adverse) reactions occur occasionally, but there is little evidence that marihuana use leads to serious mental disturbance.

Select Bibliography

Ames, F., MD., MMED 'A Clinical and Metabolic Study of Acute Intoxication with Cannabis Saliva and Its Role in the Model Psychoses.' J. Ment Sci. 1958 104: 972-99 (Oct.).

Becker, H.S. 'Outsiders. Studies in the Sociology of Deviance.' (Ch3 and Ch4.) Free Press of Glencoe, 1963.

Clark, L. D. and Nakashima, E. N. 'Experimental Studies of Marihuana' Am J Psychiat 1968 125:379-384 (Sept.)

Eddy, N. B. et at. 'Drug Dependence: its Significance and Characteristics.' Bull. Who 1965 32:721-733.

Edwards, G. 'The Problem of Cannabis Dependence.' Practitioner 1968 200:226-33 (Feb.).

Isbell, H. et al. 'Effects of (-) 9-Trans-Tetrahydrocannabinol in Man.' Psychopharmacologia (Berlin) 1967 11:184-8.

Keeler, M. H.. MD 'Marihuana Induced Hallucinations.' Dis Nerv Syst 1968 29:314-5 (May).

Keeler, M. H., MD 'Adverse Reaction to Marihuana.' Amer J Psychiat 1967 124:674-7 (Nov.).

McGlothlin, W. H., PHD and West, L. J., MD 'The Marihuana Problem: An Overview.' Amer J Psychiat 1968 125: 126-134 (Sept.).

Murphy, H. B. M. 'The Cannabis Habit. A Review of Recent Psychiatric Literature.' Bull Narcot 1963 15(1):15-23.

Zinberg, N. E. and Weil, A. 'Cannabis: The First Controlled Experiment.' New Society 1969 no. 329:84-86 (16 Jan.).