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

Chapter 7 - Cannabis: Effects and Consequences

To summarize

In Chapter 6, we have seen that use does not follow a single pattern, even less so a pattern inevitably leading to increased use. Even in chronic users, the use of cannabis is sometimes irregular and involves periods of abstinence and of more intensive use. We have also seen that current epidemiological studies are not sensitive enough to the complex interactions between the multiple factors that influence patterns of use. These various difficulties make it more difficult to estimate the number of problem users, even more so the number of persons who may become dependent.

In our view, it is clear that the term addiction, severely criticized for its medical and moral overtones, is inadequate to properly describe the different forms of at-risk and problem uses. It is even less useful when it comes to cannabis, whose addictive potential is low. It is therefore of limited use to inform public policies aiming to prevent at-risk and problem use and to assist excessive users. Further, we are of the view that dependency is but one of the many consequences of excessive use of cannabis and that this possibility must not be overestimated.

For these reasons, we propose to distinguish between different uses on the basis of four criteria: context, quantity, frequency, and duration and intensity.    


Proposed Criteria for Differentiating Use Types





Period of use and intensity

Experimental / Occasional





A few times over lifetime



Recreational, social

Mainly in evening

Mainly in a group

A few joints

Less than one gram per month

A few times per month

Spread over several years but rarely intensive


Recreational and occupational (to go to school, to go to work, for sport…) Alone, in the morning

Under 16 years of age

Between 0.1 and 1 gram per day

A few times per week, evenings, especially weekends

Spread over several years with high intensity periods


Occupational and personal problems

No self regulation of use

Over one gram per day

More than once per day

Spread over several years with several months at a time of high intensity use



Given the poor knowledge base on use patterns in Canada, we have no choice but to speculate on the number of persons falling in each of these types of uses. We propose the following broad parameters:


vv     In adults: we have estimated that approximately 100,000 persons over 18 would use cannabis daily.

··               If 30% to 40% use between 0.1 to 1 gram per day, this means that 30,000 to 40,000 may be at-risk;

··               If 5% to 10% use more than 1 gram per day, this means that 5,000 to 10,000 adults have excessive use patterns.

vv     In youth 12 to 17, we have estimated that as many as 225,000 use cannabis daily.

··               If it is agreed that any use below the age of 16 is excessive use, and that youths 12-15 who use cannabis may represent approximately 25% of this group, then about 50,000 may uses excessively;

··               Of the remaining 175,000, if 30% to 40% use 0,1 to 1 gram per day, approximately 50,000 to 70,000 would be at-risk;

··               If 5% to 10% of the remaining 175,000 use more than 1 gram per day, then approximately 8,000 to 17,000 use excessively.


We are aware that these estimates do not account other variables, such as context and duration of use. We can only hope that future epidemiological studies, which must be undertaken regularly, will help further explain the complexity and variability of these uses.




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