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Major Studies of Drugs and Drug Policy
Canadian Senate Special Committee on Illegal Drugs
Volume I - General Orientation

Chapter 6 - Users and uses: form, practice, context

Trajectories of use

Most studies identify quantity and frequency of use. Thus as we saw in the previous section, the OFDT report, for example, identifies experimentation, occasional, repeated, regular and heavy use, with frequency of use (number of times a month) and circumstances (alone or in a group, morning or evening) as the preferred indicators of at-risk use. However, this knowledge of certain characteristics of use by young people in particular tells us very little about what will follow. If we could stop time at a given moment in a user’s history, the knowledge would not help us determine what would happen next. For example, with this knowledge we could not answer the question of whether or not cannabis use begun during adolescence is part of a trajectory leading to increased use. Now, a certain number of those who testified before the Committee told us that they had observed dependence in cannabis users. Also, certain government documents, in the US in particular, do not hesitate to point in this direction by measuring requests for treatment and by reporting that requests for treatment of cannabis dependence are on the rise. For example, documents given to us by American drug authorities indicate that 40% of people who meet the DSM IV diagnostic criteria for dependence (which will be dealt with in the following chapter) have a primary diagnosis of cannabis dependence.[1][31] Unless we believe that a few occasional uses lead to dependence, we must accept that a relatively significant number of young people who try cannabis during adolescence will embark on a trajectory of use that will lead to dependence.

But what is the situation exactly? What are these trajectories of use? What are the stages? Is there a progression?

First of all, like Professor Mercier, we must point out that the idea of a trajectory is itself slightly inaccurate.


The concept of trajectory is based first of all on the basic principle whereby individuals will go through a number of stages or successive phases. It is true that the concept of trajectory is somewhat incorrect. A trajectory is somewhat of a metaphor for the trajectory of the planets and the stars, that is something very focused and in continuous motion. The word "journey" ("trajet") would be more accurate. A journey includes detours, round trips, et cetera. So we must bear in mind that this concept of trajectory is not necessarily linear, but that there will be different situations and different paths. The word "journey" is a more accurate way of describing the relationship an individual will have with psychotropic substances during his or her life. There is another important concept as well. In addition to trajectories, phases and stages, there are also transitions and passages, when individuals move from one stage to another.[2][32]


Some, like the INSERM report, speak of contact, experimentation and commitment phases. Contact is seeing cannabis or knowing people who use it. Experimentation, of course, is trying it, and may be limited to a single time. Lastly, commitment refers to the various ways of managing use, from relative commitment where there are significant changes in use to true commitment where there are fewer changes. The report specifies that these three stages are not in all trajectories and do not always follow one another in a coherent fashion. Furthermore, there will often be periods of cessation, followed by resumption or a definitive cessation. Nevertheless, according to INSERM, “commitment probably constitutes the most important stage if we want to understand what cannabis use corresponds to. However, the data on this commitment phase seems the most inconsistent as most works deal with initiation.”[3][33] [translation]

In fact, the data on committed use is still very sketchy, such that beyond a few generalities, we really know very little about the circumstances and trajectories of cannabis use. It is as if we were first worried about classifying users according to their risk of becoming dependent, or were trying to make them fit into a ready-made model. While testifying before the committee, Professor Mercier recalled the five stages in the classic pattern of addiction: initiation, gradual start of abuse, dependency, treatment and reintegration. However, as she pointed out, this is only one of the possible trajectories, the one that has been studied most frequently with regard to drugs (alcohol, heroin and cocaine in particular), and yet it hardly applies to cannabis. In any event, it is clear that with cannabis users, there is great variability in use.

The epidemiological data presented in the previous section indicate fairly clearly that cannabis use decreases significantly with age. More specifically, the rate of cessation is significant, as the following table shows.



Rate of Cessation (percentage of lifetime users who did not use cannabis in the previous year), USA, 1996 [4][34]

Age Group










35 +



















Consequently, the rate of continuation is relatively low. It was 24% in the US in 2000, 17% in Denmark, 29% in France and Germany (West), 24% in Switzerland and 8% in Sweden. The only exception is Australia with a rate of continuation of 46%.

That being said, these data says nothing about the period during which cannabis use is continued, the frequency of use or the quantities used. Epidemiological studies tend to establish that most users stop consumption during their thirties, but only ethnographic studies can provide more information. Unfortunately they are few.

The INSERM report describes studies conducted in Australia, France and the United States. Most show progress towards regulated cannabis use, that is, use both stabilized–fewer variations in use–and use more integrated into social living conditions, that is, more integrated into personal and professional life. A significant proportion of long-term regular users are men, and are more likely to be single and have creative occupations. Most say they use cannabis to relax and relieve stress, to help them sleep, or to alter their state of consciousness.[5][35]

In Canada, Hathaway studied regular users[6][36], using open-ended interviews from October 1994 to June 1995. The study involved a sample of 30 regular users (15 men and 15 women), aged 22 to 47 (average age 32). Participants had used cannabis for 3 to 31 years with the average being 17 years; 40% had used it daily for 20 years or more. This data is in complete agreement with what INSERM suggested. Long-term users integrate their regular cannabis use into their daily lives and social activities while remaining aware of the symbolic value of this “tolerable deviance”. While most started after coming into contact with a small group of users who served as more or less long-term support, the users who were most at peace with their drug use were those who regulated their use independently.


In this study, I found that moving from a pattern of use that is dependent on one’s level of participation with other users to one that is independently regulated marks a crucial transition in the marijuana user’s relationship to the drug. (…) their continuing use of the drug does not necessarily suggest an inability to commit to conventional adult roles. Instead, adapting one’s marijuana use to suit an otherwise conventional way of life appears to make the practice significant on a more personal level than that previously fostered through affiliation with marijuana-using groups. [7][37]


For a certain number of users, this acculturation of the drug occurs after a more or less prolonged period of abstinence during which they distance themselves from the group of users. This makes it possible for them to determine for themselves the role cannabis will play in their lives. Moreover, every participant in the study had managed to integrate their use into their personal or professional life. Users associate their drug use primarily with free time and relaxation after a day at work; some even compare its role with that played by alcohol. Although 97% used cannabis at least weekly and 37% used it daily, only 7% (2 people) defined their use as problematic. Most went through periods of abstinence or of decreased use without experiencing difficulties.

Another study, reported by Rigter and von Laar,[8][38] was conducted in the State of New York on a cohort of users who were followed for a period of twenty years. This study identified four types of users:

··               Early-onset heavy-use: start around age 15 and become regular users around age 17.5; daily use for a duration of 131 months on average; 49% still use around age 34-35;

··               Early-onset light-use: start around age 15 but fewer (44%) go on to daily use (for an average duration of 28 months); only 10% still use at age 34‑35;

··               Mid-onset heavy-use: start around age 16; two-thirds become daily users (average duration 42 months) and still use at age 34-35;

··               Late-onset light-use: start at age 19.5 and a minority become daily users (21%). Almost all discontinue use around age 34-35.


In all, this study shows that there were clearly more light users than heavy users. The latter had less education, went to church less often, were more likely to have a history of delinquency, and changed jobs more often. Early-onset users showed a greater tendency towards episodes of delinquency and mental disorders, started to drink and smoke tobacco sooner, had a greater tendency to experiment with other drugs, and tended to identify positive reasons for using marijuana.

But it is risky to propose typologies, because boundaries are fluid and users switch from one type of use to another fairly easily. This was shown in particular by the comparative study conducted by Cohen and Kaal in Amsterdam, San Francisco and Bremen.[9][39]

The study involved a sample of experienced users consisting of 216 people in Amsterdam, 265 in San Francisco and 55 in Bremen. The sophisticated method of selecting candidates from epidemiological studies conducted in the general population of these cities is important because it reveals the prevalence of use. The following chart shows this data.



The average age of participants varied between 33 and 37; most had a spouse and a stable job. The average age for initiation into cannabis use in the three cities was 16, that is, at a younger age than people who had only occasional exposure to cannabis (21.2 in Amsterdam and 19.5 in Bremen). Most were introduced by friends and their first experience was as part of a group. At age 19, they were regular users (at least once a month) and their heaviest use was around age 21.5. Trajectories of use were determined using six patterns:


1)1)             More to less: after an initial period of heavy use, the individual gradually decreased his use

2)2)             Gradually more: the individual gradually increased his use

3)3)             Stable: amount and frequency did not change

4)4)             Up-top-down: use increased, reached a peak, and then decreased

5)5)             Intermittent: frequent discontinuation after initiation

6)6)             Varying: use rises and falls


As the following table shows, no less than 75% of respondents in the three cities correspond to patterns 4 (48.7%) and 6 (25%).


Patterns of Use in Regular Users [10][40]



  Number              %

San Francisco

   Number              %


   Number            %


Pattern 1

Pattern 2

Pattern 3

Pattern 4

Pattern 5

Pattern 6


1717                                     8

13                    6

24                   11

     104                   48

         7                     3

       51                   24


        18                     7

        17                     6

          5                     2

       133                   50

         25                     9

         66                    25



         6                   11

         5                     9

        24                  44

          2                    4

         18                  33



During their period of heaviest use, approximately 45% of those studied used cannabis regularly. However, during the preceding year, approximately 35% used it less than once a week and more than 35% did not use it all. During the past three months, more than 50% did not use cannabis at all, and less than 10% used it on a daily basis. As for amounts, the authors of the study concluded that they are low. During their period of heavy use, less than 18% of those studied smoked more than one ounce per month, whereas during the preceding year, approximately 60% had smoked less than 4 grams (1/7 of an ounce) per month. Users were divided fairly equally between those who preferred medium or mild cannabis and those who preferred a stronger variety (with a more marked preference for the mild varieties in Amsterdam). Users have a certain number of rules regarding use: no smoking at work or school (more than 35%), during the day, or in the morning.

Most long-term users had had periods of abstinence that varied from one month to a year or longer, most often because they no longer felt the need or the desire to smoke. Moreover, between one-third and one-half had decided to decrease their use at various times.

Thus we can see that trajectories of use do not follow a linear progression, and are marked by key periods when the user integrates cannabis use into his social and personal life, distances himself from groups of users, stabilizes the role marijuana plays in his personal life, with periods of heavy use, especially at the beginning of the trajectory, followed by periods of either decreased use or of ups and downs in terms of frequency and amount.


[1][31]  Office of National Drug Control Policy (2002) National Drug Control Strategy. Washington, DC: The White House.

[2][32]  Professor Céline Mercier, testimony before the Special Senate Committee on Illegal Drugs, Canadian Senate, first session of the thirty-seventh Parliament, December 10, 2001, Issue No. 12, Page 6.

[3][33]  INSERM (2001), op. cit., page 28.

[4][34]  Rigter, H. and M. von Laar, op. cit., page 27.

[5][35]  INSERM (2001), op. cit., pages 55-58.

[6][36]  Hathaway A. D. (1997a) “Marijuana and lifestyle: exploring tolerable deviance.” Deviant Behaviour: An Interdisciplinary Journal, 18, pages 213-232; and (1997b) “Marijuana and tolerance: revisiting Becker’s sources of control.” ibid, pages 103-124.

[7][37]  Hathaway, A.D. (1997a), op. cit., page 219.

[8][38]  Rigter, H. and M. von Laar, op. cit., pages 28-29.

[9][39]  Cohen, P.D.A. and H.L. Kaal, The irrelevance of drug policy.  Patterns and careers of experienced cannabis use in the population of Amsterdam, San Francisco and Bremen. Amsterdam: University of Amsterdam, CEDRO.

[10][40]  Ibid., page 48.

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