Drug Abuse

Cannabis Control Policy: A Discussion Paper

Health Protection Branch

Department of National Health and Welfare

January 1979

Part 3 – The Empirical Bases of Cannabis Control Policy

A meaningful discussion of cannabis policy must be founded on reliable information as to the effects of the drug, the epidemiology of its use, and the institutional characteristics and socio-legal consequences of our present control regime. These matters are addressed in the following subsections: Chapter 1 surveys the available evidence regarding the correlates of cannabis use, while Chapter 2 summarizes the data pertaining to our current legislative response.

1. empirical Evidence Regarding Cannabis Use

Cannabis sativa is an herbaceous annual plant which grows as a weed or is cultivated throughout the tropical and temperate areas of the globe; it is commonly referred to as "Indian Hemp." Marijuana consists of the crushed leaves and often small twigs or flower tops and is usually smoked, either by itself or mixed with tobacco. Hashish, which is generally more potent, is the resin of the plant which has been squeezed or scraped from the leaves or flowering tops. It is sometimes eaten, but usually smoked in a pipe or sprinkled on tobacco and rolled into a cigarette. Hash oil, an extract of the resin, is mixed with tobacco or low-grade marijuana to be smoked, or smeared on cigarette papers to be used in the manufacture of "joints." The pharmacological effects of cannabis are due primarily to 1-D⁹-tetrahydrocannabinol (THC) and certain related metabolites.

In the following section we canvass the major findings of our background studies and literature reviews of the use of cannabis. This survey includes discussions of: (a) health concerns; (b) safety concerns; (c) the cannabis market; (d) extent of use; and (e) patterns of use.

Health Concerns

One of the major areas of concern surrounding cannabis pertains to its physiological and psychological effects, especially under conditions of heavy or prolonged use. Unfortunately, several important hypotheses have only begun to be explored, the scientific literature is riddled with inconsistent, methodologically questionable and unreplicated research, and North American-based long-term studies have yet to commence. Further, in some areas the proponents and opponents of cannabis law reform are locked in a prolonged and unproductive debate as to the meaning, significance and epidemiological implications of reported effects. As Griffith Edwards (1974:8) has commented: "in this polarized situation, objectivity becomes the casualty."

For the past decade, however, there has been an intensive international effort to determine what, if any, biomedical liabilities result from the use of cannabis. There remains much to be learned, but a considerable body of reliable knowledge of cannabis effects — adverse and otherwise — has accumulated. A review of these materials for the Health Protection Branch has been prepared by Dr. Leo Hollister, a California pharmacologist and one of a very small number of universally respected researchers in this field. We have also received advice and assistance in this area, especially as it relates to the Canadian context, from Dr. Ralph Miller, former Research Director of the Le Dain Commission of Inquiry into the Non-Medical Use of Drugs.

The evidence to date suggests that cannabis is relatively safe, but we must proceed on the assumption that it is not a unique drug in having no detrimental effects on health. Indeed, there are a number of possible health hazards which must be addressed.

Recent controlled field studies (all of which were conducted outside of North America) have generally failed to detect any major health consequences from long-term heavy cannabis use, but in certain circumstances the research techniques were too limited and the samples too small for accurate epidemiological predictions regarding unusual or statistically rare conditions. If cannabis is at all like alcohol or tobacco in its health hazards, broader-based epidemiological studies will be necessary before any final conclusions can be reached in certain areas.

Since there is little evidence of any significant health problems caused by moderate use of cannabis by normal young adults, attention in this review is placed primarily on possible effects of heavy, chronic use, and on use by particular subgroups of Canadian society who may have specific susceptibilities to any potential health problems. Impairment of psychomotor functioning, and its relationship to the safe operation of motor vehicles, is one issue of major importance to public health, but discussion of this problem will be deferred to a later section on safety-related concerns associated with cannabis use. First, we will focus on physiological effects. Later in this section, we will deal with the psychological and mental health aspects of cannabis use.

It seems to be generally agreed that the most likely health problem associated with cannabis use derives from its most common mode of administration (smoking) and the consequent risk of bronchial or pulmonary damage. It appears that heavy cannabis use may have effects similar to tobacco in this regard. This problem is especially exacerbated by the additional risk that some samples of marijuana may be contaminated by paraquet, an herbicide which may be extremely toxic when inhaled. Consequently, cannabis smoking by persons with impaired pulmonary function appears to be hazardous; frequent, chronic use of the drug in this way should be avoided. However, at present it is much more difficult to find evidence of clinically important pulmonary insufficiency among cannabis smokers than for example, among those who regularly smoke tobacco.

Concern about other probable health hazards is primarily focused on particular subgroups of society. The acute effects of cannabis, including increased heart rate and other ordinarily minor cardiovascular effects may have deleterious consequences for those suffering from arteriosclerosis of the coronary arteries, congestive heart failure or other cardiovascular disorders. Possible effects on the hepatic enzyme system may be problematic for persons with preexisting liver disorders.

There are other areas where the degree of risk involved in cannabis use is less certain than in those discussed above, but nonetheless deserve careful appraisal. Three of these again apply to special population groups: pubescent boys, pregnant women and diabetics.

Concern about cannabis use by young boys initially arose from some contradictory clinical observations of decreased serum testosterone levels in male cannabis smokers. Experimental studies have been similarly suggestive, but inconsistent. Although the evidence is not clear and its potential significance yet to be determined, the limited endocrine changes indicated, although probably of relatively little consequence in adults, could be of major importance in the prepubertal male.

Cannabis, like many other drugs, crosses the placental barrier, and although there is no demonstrated association between its use during pregnancy and fetal abnormalities, such occurrences, if they exist, are likely to be statistically rare and might easily be missed. Use during pregnancy should therefore be discouraged, although, as Dr. Hollister has noted, the "...current admonition against using cannabis during pregnancy is based more on ignorance than on definite proof of harm."

It has been suggested that large doses of THC might aggravate diabetes through deterioration of glucose tolerance. Such a relationship has not been clinically demonstrated, but the paucity of clinical evidence may be due to the relatively low doses commonly consumed by users or to some development of tolerance to this particular pharmacologic effect.

Other hypothesized, but so far unresolved, health hazards apply to the cannabis-using population as a whole. Impairment of cell-mediated immune responses has been suggested by some studies, but the experimental evidence is inconsistent and greater disease susceptibility in cannabis smokers has not been observed. . If such reductions do occur, they may well be transient, or so small that the capacity of the body to resist challenge is not sufficiently depleted to be cause for concern. The issue, nonetheless, warrants further research. The controversy over chromosome damage also remains to be resolved for cannabis, and, for that matter, a variety of commonly used drugs, including aspirin. In the absence of clinical evidence of harm, the significance of any abnormalities which may emerge is doubtful, but current uncertainty will only be assuaged by further experimental work. Similarly, research into the effects of cannabis on cell physiology and metabolism has failed, as yet, to provide us with satisfactory information on the role of the drug as a potential cause of lung cancer. Some findings suggest that the tars in cannabis smoke might be carcinogenic. Other cell studies indicate that THC might be therapeutically useful in the treatment of malignancies.

In the light of recent research findings, some issues which were once considered important do not now seem to warrant particular concern. An early study which reported brain atrophy in cannabis users has not been confirmed by newer and more reliable techniques, and epidemiological surveys have been generally unable to find clear evidence of impaired brain function in heavy cannabis users. It also appears unlikely that the high lipid solubility of THC implies that sequestered quantities of the drug might be later released in an active form. Many widely used drugs, including diazepam (Valium®) are highly lipid soluble, but this does not necessarily mean that the drug is accumulated in any active form or causes problems as a result of this characteristic per se. However, high lipid solubility, in this case, must be seen as grounds for continued, careful observation.

Dr. Hollister has come to the conclusion that "... general toxicity studies of cannabis and its constituents lead to the inescapable conclusion that it is one of the safest drugs ever studied in this way."

Turning now to the area of mental health and psychological functioning, it has been suggested that there might be some risk in the use of cannabis by psychologically troubled persons, whose psychiatric problems might be unmasked or aggravated by the drug. Tolerance to the effects of cannabis and definite, although mild, signs of physical dependence have been experimentally observed. These occur at much higher levels of consumption than those which characterize typical recreational cannabis use, but we cannot ignore the possibility that certain persons may be prone to compulsive use of this drug, as with any drug with attractive psychopharmacological characteristics.

One of the most common concerns is that cannabis use may precipitate basic changes in the personalties of users, whereby they become less motivated to work or strive for success. This so-called "amotivational syndrome," although observed in some young people who have become preoccupied with drug-taking and have radically changed or abandoned traditional life goals, is difficult to attribute directly to cannabis, especially when multiple drug use is present. In contrast to pharmacological hypotheses regarding such occurrences, other researchers have suggested that lack of motivation is really a manifestation of concurrent depression for which cannabis may be a self-prescribed treatment. No clear evidence exists for either mechanism, however. It has also been found that family background and relationships, as well as social values, are much. stronger predictors of dropping out of college than is drug use. Participation in the illicit drug subculture and "amotivation" may both be symptomatic of the same underlying problem. It is clearly impossible to ascertain if these lifestyle changes, when they do occur, are caused by the pharmacological properties of cannabis.

Whether or not cannabis has the ability to evoke sociopathic, depressive or schizophrenic states is highly uncertain, but there is little empirical evidence that this is a significant risk. There is no doubt that, in certain situations, it can produce acute anxiety or panic reactions. Although such transient reactions occur infrequently, if at all, in regular users, they are probably the most common adverse psychological effects of the drug. Fortunately, these reactions are rapidly reversible as the effects of the drug wane. Toxic delirium and acute paranoid states, more serious and more rare, are similarly self-limiting. "Flashback" reactions tend to be mild and require no specific treatment. At the present time, it would appear that psychopathology may predispose certain people to problematic cannabis use, rather than being caused by it. As mentioned above, it is reasonable to assume that it might unmask latent psychiatric disorders in those who are particularly vulnerable, but it does not appear that this is a significant occurrence in the general population.

Evidence from the available health statistics suggests the limited scope of cannabis-related psychological problems. For example, roughly one hundred cases involving cannabis are reported each year to the National Poison Control Program, representing 0.1%-0.2% of all reported poisonings. Even then, the figure is probably inflated, since patient reports are accepted without independent chemical verification. A 1975 study in a Toronto emergency ward indicated that adverse cannabis reactions (chiefly acute panic reactions) were concentrated among young, and probably naive, users; less than 3% of the alcohol and other drug-related emergencies requiring institutional intervention involved cannabis. Similarly, cases involving cannabis constituted less than 4% of all 1976 "crisis contacts" at the Calgary Information and Crisis Centre. This represented less than one-tenth of the number of cannabis cases reported there in 1972, despite a steady increase in the prevalence of cannabis use during the intervening period.

While 19% of all psychiatric admissions in Canada are classified as due to "drug dependence" by the Mental Health Division of Statistics Canada, all but 2% were attributable to alcohol, the cannabis-related admissions constituting 0.03% of the country's psychiatric case load. (About 30 cases per year over the past six years). Further, most cannabis-related admissions result in very brief hospital stays, usually measured in days or weeks, and some admissions may be attributed to cannabis in lieu of other more appropriate diagnostic assignments. Despite considerable increases in the using population, the proportion of psychiatric admissions attributed to cannabis has not risen accordingly. These more recent data seem to reinforce the Le Dain Commission's 1972 conclusion that:

...cannabis does appear as a secondary or complicating factor in psychiatric admissions in Canada, although such cases do not represent a significant proportion of either cannabis users in general or of the psychiatric hospital patient population in particular. (Le Dain, 1972:90)

There is no currently accepted medical use of cannabis in Canada, outside of the experimental context, although it appears that therapeutic prescription by physicians is not prohibited by law. Production of the last cannabis-containing pharmaceuticals was discontinued in 1954 and no new supplies have been made available through traditional channels. While cannabinoids, over the centuries, have been reported to produce an incredible array of possibly useful medicinal effects, the majority of the alleged effects are either complicated by undesirable side effects or can be duplicated by other more readily available and convenient drugs. Recent advances in the synthesis of natural cannabinoids and related compounds has led to a new generation of clinical testing. Some potentially important therapeutic uses have been discovered and a few interesting leads from the earlier literature have yet to be adequately followed up using modern techniques.

Of primary interest is the ability of THC to lower intraocular pressure in glaucoma, a major cause of blindness, and its capacity to suppress the often debilitating nausea and vomiting associated with cancer chemotherapy. Areas where cannabinoids are currently being investigated for possible, but less likely, clinically useful effects include its use as a bronchodilator in the treatment of asthma, as a tumour growth inhibitor in cancer treatment, and as an appetite stimulant in anorexia disorders. Other more tenuous uses include possible anticonvulsant and analgesic applications.

Major health hazards of cannabis have not readily appeared in either field studies or clinical practice, but we cannot rule out the possibility of statistically rare or as yet unforeseen occurrences. Like tobacco cannabis smoke contains tars which can be damaging to the lungs, and paraquat-contaminated materials are likely to be quite toxic. Until definitive research results are obtained concern will continue over the use of cannabis by people with heart, lung, or liver problems, diabetics, pregnant women, and young boys. Although our mental health and toxic reaction statistics would indicate that cannabis is of relatively little importance in precipitating problems in these areas, use by certain emotionally unstable people may be unwise. Overall, the risks to health connected with cannabis use appear, at present, to be less significant than those related to the use of the more common recreational drugs, but until further research has been conducted, caution and vigilance would be recommended.

Safety Concerns

Safety is of major importance warranting independent consideration for a number of reasons. Although the impaired driver may be putting himself at risk, he may potentially harm others as well, so our concern here is now focused on risk of harm to others which may arise from cannabis use. Secondly, direct "harm to others" describes a moral category of behaviour that all schools of legal philosophy agree justifies the use of the criminal law power. Finally concern about safety raises a host of self-contained legal problems that deserve special attention.

The cannabis and safety issue primarily involves the operation of motor vehicles on the roads. The use of heavy machinery and flying are further illustrations of situations where cannabis use may compromise performance and thus put the safety of others at risk. Driving, however, remains the archetypal, most commonly occurring, and best-researched example of an activity which can endanger public safety. In addition, its apparent resemblance to the alcohol-and-driving situation has prompted considerable public discussion and a concomitant search for a "Breathalyzer" type of testing device, on the assumption that the problems anticipated will indeed occur.

A thorough review of the relevant research findings in this very complex field has recently been completed by R.A. Warren, a Research Associate at the Ottawa-based Traffic Injury Research Foundation. In general, his findings confirm the research and literature review presented by the Le Dain Commission in its 1972 Cannabis report.

In order to investigate possible traffic safety hazards associated with cannabis use, two major methodological strategies, experimental and epidemiological, have been adopted, each with its special strengths and weaknesses. Experimental studies are designed to investigate, under carefully controlled conditions, the potential cannabis effects on certain psychomotor skills thought to be important in safe driving. Epidemiological studies, on the other hand, search for evidence of already-existing "real world" involvement of cannabis in problematic driving, by examining users' attitudes or experiences, studying driving records, and systematically investigating accidents.

Epidemiological studies are frequently very difficult to control properly and can generally yield reliable predictive information only if the incidence of drug use in the driver population is already fairly substantial. To date, no comprehensive studies of cannabis involvement in traffic accidents have been undertaken, although a number of limited efforts have been made. There is some evidence of an association between cannabis and driving mishaps, but the data are inconsistent. Other studies have not found evidence of such a relationship.

Care must be taken in interpreting limited or inadequately controlled epidemiological studies. For example, an apparent relationship between accidents and persons who have chosen to drive after consuming an illegal drug may derive from other preexisting characteristics, such as risk-taking tendencies, rather than resulting from the use of the drug. Age, sex and region are also essential factors which must be controlled.

Studies where active drug levels in the bodies of persons involved in accidents are compared with drug levels in control subjects who have not been associated with driving mishaps have been of primary importance in clarifying the traffic hazards of alcohol. However, there are chemical and pharmacological differences inherent in the cannabis situation which limit the feasibility of such an approach.

Considerable attention has been given to the possible development of a quantitative chemical test analogous to the Breathalyzer, which could provide a reasonable estimate of the intensity of current cannabis effects. Such a device would be invaluable for basic experimental and epidemiological research, as well as for traffic law enforcement. Although qualitative methods exist that can provide some evidence of fairly recent use (e.g., employing ether finger swabs, mouthwashes, dental scrapings and urine samples), these sampling techniques are often not appropriate and, in any event, cannot provide quantitative information regarding current effect levels. In fact, they cannot generally discriminate use immediately before testing from use several days prior to taking the sample.

Available evidence, based primarily on the relatively simple case of isolated THC administration, suggest that blood sample analysis is the most practical approach to estimating the intensity of effects from levels of cannabinoids in the body. However, current methods have little applicability outside the laboratory. Even if simplified and efficient blood sample techniques were developed, significant practical and legal problems surrounding the acquisition of appropriate samples would likely preclude their use for general traffic control purposes.

In the review noted above, Warren (1978) concluded that a causal relationship between cannabis use and driving impairment has not been demonstrated and that at present no epidemiological evidence that cannabis contributes to driving collisions has been found.

Since completing this review, Warren has submitted a confidential interim report on a project investigating the level of drugs in fluid and tissue specimens from persons killed in traffic accidents in Ontario over the past year. Evidence of cannabis use was found in a significant number of the victims. It is difficult to interpret this aspect of the study, due to the small numbers involved and the preliminary nature of the report. Disclosure of more complete results is anticipated later in the year.

There are different problems involved in the evaluation of experimental studies deriving from the fact that little is known about the actual causes of traffic accidents, and small changes in one or more of the complex of driving-related skills might not be significantly related to accidents or injuries under natural conditions. It appears that such factors as driver attitudes, risk-taking traits, aggression, judgement, attention and susceptibility to distraction, and a variety of other psychological variables which are difficult to measure may be more significant in contributing to automobile accidents than are elementary psychomotor skills. Therefore, although certain basic driving parameters can be established experimentally and important issues raised, such studies can provide only a limited basis for predicting the likely "real-world" effects.

Laboratory research indicates that cannabis can produce dose-dependent short-term deficits in certain perceptual, attentional, cognitive and psychomotor abilities which are of possible significance to driving. Similarly, a few studies have revealed that experienced airplane pilots undergo deterioration in performance on flight simulators after smoking high doses of marijuana. Several experiments have demonstrated analogous detrimental effects of cannabis on certain automobile driving tasks, on test tracks and on the road. Further, it appears that alcohol and cannabis have additive deleterious effects on driving skills when used together. On the other hand, several reports suggest that cannabis reduces aggression and risk-taking in a variety of situations. Taken as a whole, these experimental findings are certainly cause for concerned attention, although, as noted above, they cannot be used to directly predict traffic hazards under natural conditions.

Surveys suggest that among regular cannabis users driving while high is not uncommon and that the combined use of alcohol and cannabis in a variety of situations is becoming increasingly frequent. In spite of the inconclusiveness of current findings, research suggests a cautious, rather than optimistic, approach to the issue of cannabis and driving.

The Cannabis Market

Despite intensive efforts to eradicate the cannabis trade, marijuana, hashish and hash oil are probably more readily available now than at any other time in Canadian history. Large international networks, capable of smuggling literally tons of cannabis into the country in a single venture, have evolved over the post decade, and substantial seizures and severe penalties appear to have had little or no effect on national availability.

Prices have tended to stabilize recently, domestic cultivation has expanded, and marijuana, the most common cannabis product, has tended to increase in potency as once-rare strains and more discriminating tastes have come to characterize the retail market.

The source countries for the Canadian market have remained the same over the decade, although there has been some reordering in terms of the amounts contributed by each country. Hashish still comes from the Middle East, North Africa and parts of Asia; Mexico, Colombia and Jamaica are the major sources of marijuana. In recent years, however, the Mexican marijuana trade has become disrupted because of intensified enforcement efforts, including the herbicide-spraying programme and increased border and coastal patrols. Consequently, many smuggling organizations simply shifted to countries such as Colombia, now Canada's largest contributor of marijuana, where the crops are less physically vulnerable or regimes more hospitable.

This reordering of source countries has had a number of effects. The size and sophistication of smuggling operations has increased. In addition, there has been a marked increase in the potency of the marijuana available in Canada, since the more equatorial locales generally produce plants superior in THC content to most Mexican cannabis. The available data suggest a three- to fivefold increase in average marijuana potency over the past seven years. In this same relatively brief period, the strength of the hashish typically available in this country appears to have declined to the point where it is more or less equivalent to that of marijuana, suggesting the difficulties of chemically or legally distinguishing between these two cannabis products on the basis of potency alone.

Initially, domestic cultivation of cannabis operated on a relatively small scale, but by 1976, commercial production had become a significant factor. Although domestic cannabis is not particularly popular among consumers at present, it will become increasingly marketable as growers develop the experience and technology necessary to produce more potent varieties, or in the unlikely event of a sustained shortage of foreign supplies.

Even if the present sources of supply were eliminated, there is no shortage of possible countries in which cannabis could be grown. In many regions, cannabis cultivation provides a higher return per unit of land and per unit of labour than even poppy cultivation. The possibility of finding a viable crop substitute or developing an income replacement programme for cannabis cultivation is extremely bleak in the foreseeable future. The likelihood of greatly improving cannabis enforcement in the potential source countries is also discouraging.

The young entrepreneurs of the 1960s, who imported relatively small quantities of cannabis, are being increasingly replaced by older and more experienced smugglers involved in large-scale operations. However, cannabis importers tend to be less sophisticated than their counterparts in the heroin trade, and the market does not appear to be linked to organized crime syndicates, such as the Mafia. It is assumed that the lion's share of the domestic market is met by these large-scale importing operations; smaller importers continue to operate, and become particularly important when the market is disrupted.

Some violence does erupt in the cannabis market from time to time, but these episodes seem to be chiefly related to cheating or theft, rather than territorial rivalry. Upper level distributors tend to deal only in cannabis; however, some retail dealers also handle other illicit drugs, including amphetamines and LSD. There appears to be little overlap between the cannabis and opiate narcotics distribution systems.

Within Canada, the marketing systems for hashish and marijuana are similar, although on the upper levels of distribution they are largely discrete entities. The larger the initial quantity that arrives in Canada, the more numerous are the levels of distribution between importer and consumer. Each level of distribution involves different financial risks and chances of detection and arrest, as well as different profit margins. At the lower levels, financial returns are so small that only those committed to using cannabis would bother to become involved. The return for some dealers is solely realized in cheap or free supplies for personal use; indeed, many so called "dealers" operate only or primarily to ensure themselves and their immediate friends a continuous supply of cannabis at bulk-purchase prices.

Any effort to reduce cannabis consumption must include measures directed at the reduction of both supply and demand. Supply, however, does not appear to be significantly influenced by either expensive interdiction methods or repressive sanctions.

During the last ten years, Canadian law enforcement resources devoted to cannabis have probably increased twentyfold. While this upsurge in resources has increased cannabis arrests by more than 1000 percent, there has been no significant increase in the price of cannabis products in relation to disposable income, no sustained shortages of marijuana, and only temporary regional shortages of hashish.

These disappointing results are attributable to a number of factors. There are almost no serious barriers to entering the cannabis importing business or participating in the distribution system. The profit margins in the illicit traffic are powerful inducements, even in the face of severely punitive sanctions. The underground romance of dealing cannot be discounted as a motivating factor.

In summary, our experience since the late 1960s strongly suggests that the Canadian cannabis market is largely immune to increasing arrests, raids, and other law enforcement efforts. The resilience of the international and national cannabis markets in the face of sophisticated enforcement endeavours suggests that Canadian demand is unlikely to exceed supply, in the foreseeable future.

Extent of Use

In the previous section, we addressed the problems surrounding the control of the supply of cannabis in Canada. Here, and in the section which follows, we consider the nature of the demand: how many Canadians consume cannabis and how the size and composition of this population has changed in recent years.

Widespread use of cannabis did not occur in Canada until the mid-1960s, but since that time the number of users has grown dramatically. Uniform trend data is, unfortunately, not available, but there have been two national household surveys and a number of regional studies, most commonly of school populations, from which to draw broad conclusions.

The first nationwide survey, in 1970, was sponsored by the Le Dain Commission. It gathered a certain amount of retrospective data for the years 1966 to 1970 which indicated that the proportion of adult Canadians who had tried the drug, or had "ever" used it, had risen from 0.6% to 3.4% during that period. A Gallup survey, commissioned by the Non-Medical Use of Drugs Directorate and conducted in January of 1978, revealed that this "ever used" category had risen to just over 17%, indicating that just over 2,750,000 adult Canadians had consumed cannabis at least once.

Of more relevance, however, are measures of the number of people who are "current" users, that is, those who have taken cannabis within a specified time period (usually six months or a year) prior to being surveyed. Indeed, at the time of the 1970 survey, about 2.4% of adults claimed to have stopped, leaving only 1% currently using, little more than 125,000 people. These figures had changed considerably by early 1978, with over l½ million Canadians aged eighteen and over (9.7%) having used within the past year, and almost as many (1.33 million or 8.3%) having done so within the month prior to interview.

The population bases of these two national surveys are not strictly comparable, but the percentage increase suggested is large enough to indicate substantial growth in the cannabis-using population.

In addition, there is reason to believe that these are minimal estimates, for the sampling methodologies employed by household surveys tend to identify people who spend much of their time in the home and underrepresent younger and more socially active people. On the basis of what we know about the characteristics of cannabis users, it is not unreasonable to hypothesize that many would fall into these two categories. The very nature of the household survey also excludes those who live in college dormitories; this is likely to be a significant omission, as the 1970 household data were supplemented with a survey of university students which yielded the highest use rates in Canada. In addition, the national surveys leave out people who live in hospitals, prisons and other institutions, as well as the more geographically mobile, or hostel-dwelling, citizens.

Nonetheless, these findings indicate that a large and growing number of persons use or have used cannabis. In addition, a significant proportion of current users smoke fairly regularly. The 1978 data suggest that close to 600,000 adults had smoked cannabis in the week prior to interview; somewhat less than half of this group, representing about 1.4% of adults, had used every day in the preceding month. The results of two surveys of Ontario adults, sponsored by the Addiction Research Foundation, suggest that adult cannabis use may be increasing at a faster rate today than was the case in the late 1960s and early 1970s. The incidence of current users rose from 5.8% in 1976 to 8.6% in 1977. The 1978 Gallup data for Ontario would indicate a further rise to 11.5% last year, implying that 3% of the adult population was recruited into use each year and that, in just two years, the proportion of adult Ontarians who had used cannabis sometime in the past twelve months had doubled. It is clear that cannabis use is not just a phenomenon of the 1960s, and is not confined to students and other young people.

Turning to adolescent Canadians, the surveys sponsored by the Le Dain Commission found that 11%, just under 300,000 teenagers, were cannabis users in the spring of 1970. (Le Dain, 1972: 204) There has not been a national survey of secondary school students since, but there are sufficiently comparable regional surveys to roughly piece together countrywide estimates. With some regional variations, these local and provincial polls show a steady growth in the incidence of cannabis use among high school students.

Research involving students usually identifies percentages of students who have used within six months or one year of the survey. "Ever used" data are only available for Vancouver secondary school students; in 1978, roughly 47% said they had ever tried cannabis, up 8% from the 1970 figure.

"Current use" figures vary considerably, depending on the year the research was conducted and the city or region covered. One consistent observation, nevertheless, is that the proportion of students using cannabis seems to increase yearly. In the early years of the decade, users generally represented 10-20% of secondary school students. In the past three years, studies have been obtaining figures of 20-30% for the most part, with a low figure of 15% for Prince Edward Island, and a recent high of 37% from Vancouver. Our only national data on high school students were obtained in 1970 (Le Dain, 1972: 203) and indicated that about 2% were using at the end of 1968. It is clear that this decade has, indeed, seen a dramatic increase in cannabis use by teenagers.

Although student surveys consistently reveal that cannabis use increases with age or grade, it is by no means confined to the older students: up to 13% of some samples of those in grade 7 (or aged 12) have been found to be using, with most surveys suggesting about 5% for this age group. The range for 17-year-olds (or those in grade 12) tends to be 35-45% using at least once in the six months prior to the research. Less than 10% of all students use once per week or more often. Although this implies that over one-third of current student users smoke with some degree of regularity, "once per week," certainly, could not be characterized as very "heavy" use.

The data do not permit accurate estimates of the number of young people using cannabis. However, it is probably safe to assume that 25% of high school students used marijuana or hashish sometime in 1978. This would place one million or more teenagers in the present using population.

Combining the teenagers with the adult population figures, one could conservatively estimate that 2,750,000 Canadians have used cannabis in the past year, 1,750,000 adults and one million teenagers. Considering some of the sampling problems involved in household surveys, that there is no indication that recent increases in incidence have reached a plateau, and that the student use estimates are necessarily lacking in precision, it is well within the realm of possibility that the current using population numbers 3½ million or more. It would certainly not seem unreasonable to suggest that there are 3 million current users, representing one in seven (15%) Canadians aged ten or over. As the adolescent using population continues to grow and as older adult non-users are demographically replaced by maturing users, it appears that cannabis users will constitute an increasingly large proportion of the Canadian population.

Patterns of Use

It is necessary to identify the various patterns of cannabis use, if we wish to meaningfully understand the phenomenon in Canada. Most classification systems are based on the frequency with which the drug is used, the persistence or duration of use, and often some suggestion as to the role and meaning of cannabis in the user's social and personal life.

In the foregoing section, we distinguished between people who had "ever" used cannabis, to indicate how widespread was personal contact and experience with the drug, and "current" users, who had consumed cannabis within a year or six months of being surveyed. Within this latter category are people who may be called experimental users, who may have smoked cannabis once, or several times, but have not yet established the role it will play in their lives, if any. There may also be found those casual (or episodic) users, who enjoy the use of cannabis in certain situations, probably at the invitation of more regular smokers, but do not maintain their own source of supply. Occasional users may purchase cannabis from time to time, or even quite regularly, but tend to be selective about the contexts in which they use (special social occasions, on weekends, with certain friends, etc.) and tend to use less frequently than regular users. Those in the latter category have more thoroughly integrated the use of cannabis into their lives, usually keep a quantity of it on hand, and tend to smoke in a variety of social and personal situations, some, but not all, smoking every day.

It is worth noting here that many cannabis users switch from one category to another or stop using altogether; occasional users become episodic and vice versa, regular users become occasional, and so on. One of the encouraging aspects of cannabis use patterns is the apparent ease with which people move out of the cannabis-using population. Some, often after extensive use of the drug, discover that they are no longer enjoying it sufficiently to continue or that unpleasant reactions tend to predominate. In most cannabis-using circles, certainly amongst mature users, it is quite acceptable to pass along the cigarette or pipe without partaking, and such occurrences usually go by unremarked. Some people stop as a result of other life style changes, often drifting away without having made a definite decision to refrain from use.

The survey data do not inquire deeply into the role of cannabis in users' lives, but there is some anecdotal and observational information available, and it is probable that frequency-of-use is a fairly good indicator of seriousness of involvement. The 1978 Gallup national household study found that a large proportion (over 85%) of the adults who had used any cannabis in the year prior to interview had also used within the previous month. It indicated, however, that less than one-half of the current adult cannabis users were smoking as often as once per week. As mentioned above, most student surveys reveal that somewhat more than one-third of adolescent users smoke once per week or more frequently. Less than 15% of adult users claim to use on a daily basis, but it would appear that most of these confine their cannabis smoking to weekends and evenings. Only a very small proportion of users (1-2%, by one estimate) would seem to use frequently enough to be under the influence of cannabis for most of their waking hours.

Indeed, most cannabis use seems to be recreational and social, engaged in by persons of like interests, as a complement to other shared activities. Most use occurs in private settings, but some events and social occasions are associated with public consumption: certain concerts, films or youth-oriented bars, for example. Use in public is rarely indiscriminate, however, and usually occurs where cannabis users constitute a large proportion of those present and where they believe themselves to be substantially immune to arrest.

Although public consumption is less common than private, it is more likely to be followed by driving while under the influence of cannabis. It is thought that a substantial proportion of cannabis users prefer to avoid driving in this condition (Kahn, 1978:8), yet it has been estimated that between 50% and 80% have done so at some time. As indicated earlier, the highway accident implications of this have yet to be determined, but are a source of some concern, especially when alcohol has also been imbibed before taking to the roads.

The full implications of patterns of cannabis use in Canada await further research and the passage of several more years. There is no indication that recent increases in the using population have begun to level off. One might postulate, however, that we have already passed through the period in which the worst, at least short-term, consequences of cannabis use could have been expected to reveal themselves. In its beginnings, cannabis found favour among the young, the rebellious, and those on the margins of Canadian society. That it has now moved into the households of "ordinary" citizens raises concerns about road safety, increases in conviction rates for cannabis and the unhappy consequences that may result, and perhaps, some long-range health hazard which has not yet become apparent. However, remarkably few "victims" of cannabis use have emerged over the past fifteen years, when a large proportion of users were among the least mature, responsible and socially integrated of our citizens. Despite the widespread availability of cannabis, at prices which are low in relation to disposable incomes, the majority of users maintain casual or occasional patterns of use. Bearing these considerations in mind, perhaps we can anticipate future dissemination of cannabis use in Canada with cautious reserve, but with minimal trepidation.

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