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Cannabis Effects and Dependency Concerns in Long-term Frequent Users:

A Missing Piece of the Public Health Puzzle

Andrew D. Hathaway, Ph.D.

Centre for Addiction and Mental Health*
33 Russell Street, Toronto, Ontario
Canada, M5S 2S1

*The views expressed in this paper are those of the author and do not necessarily reflect those of the host institution.

N.B.: The following manuscript is under peer review in the journal Addiction. Accompanying tables have been omitted for present purposes, but will be made available to the Committee in their entirety on publication.


Aim. To elucidate the consequences of cannabis use in terms of perceived benefits, as well as the personal costs including dependency that are linked to frequent drug use. Setting and Participants. One hundred and four experienced cannabis users residing in Toronto, Canada were recruited to take part in face-to-face structured interviews. Measurements. An in-depth questionnaire developed for use in a previous study* of cannabis use patterns and correlates was administered. Advantages and disadvantages of use, covering positive and negative effects and physical symptoms of drug use in general, were measured and ranked in order of reported prevalence. The frequency of DSM-IV inspired criteria among other cannabis dependency indicators was also examined. Findings. Perceived positive effects or advantages of using cannabis tend to outweigh negative use outcomes. The most prevalent reasons for use pertain to relaxation and enhancement of recreational activities followed by coping with stress and anxiety. Cannabis effects that are relevant for some are not experienced at all by other users. Other use effects are more contingent on the circumstances. The frequency of respiratory and throat problems attributed to using cannabis underscores the perceived risk of pulmonary damage due to long-term heavy use. Analysis of dependency criteria shows higher concern among users about levels of use per se than for their impact on personal health, social responsibilities, or other conventional activities. No association was found, however, between amounts or frequency of use and the number of reported DSM-IV items. Conclusion. Experienced cannabis users weigh the costs and benefits of use and tend to find in favour of the latter. Certain disadvantages, including the potential for dependence, are nonetheless acknowledged and accepted by users, with use levels adapted accordingly when seen as problematic.



The author is indebted to Craig Reinarman and colleagues for permission to use their San Francisco drug use questionnaire for present study purposes. Patricia Erickson provided helpful comments on an earlier draft of this paper.



Of all the illicit drugs, cannabis is most often characterized as relatively benign in terms of social and personal harms due to use. Although cannabis use is not without health risks, cumulative evidence about its low addictive property, infrequent consumption by most users, and few adverse behavioural and health effects at low use levels, have maintained its low risk profile., Next to its other illicit drug counterparts, apart from recent evidence on the respiratory hazards of long-term heavy use,,, far less detailed study is devoted to other adverse consequences. Thus, while invariably the first drug proposed for legal initiatives during any discussion of drug policy, compared to heroin, cocaine, and other drugs that are generally agreed to be more addictive and harmful, cannabis is seldom prominently discussed in the context of public health, or ‘harm reduction,’ priorities.

The issue of cannabis dependency in particular is often allayed by assertion that the drug is only mildly habit-forming and lacks the physical dependence producing potential found in many other drugs. Movement toward decriminalization in Australia and several western European jurisdictions, however, coupled with opposing claims that the cannabis today is of much higher potency and more dangerous than once thought, has served to reinvigorate a long-standing policy debate as to its harms. The question of drug dependence among other legitimate public health concerns is especially complicated for cannabis when compared to other substances. Despite the reassuring claims of policy reformers, its reputation as a ‘soft drug’ (claimed to be no more harmful than tobacco or alcohol, for example) does little to alleviate these concerns in light of the substantial health and social costs incurred by the latter legal substances.

Addressing the health of individual population groups depends heavily on the quality of data available on those groups and how each of them reacts to various health and social stressors. Better targeting and tailoring of prevention and voluntary treatment programs requires more detailed information on how and why cannabis is used, by whom, and with what adverse consequences. Traditional approaches to drug education and treatment tend to adopt a ‘mechanistic view’ of drug abuse and addiction in which passive users become compulsive and persist despite consequent harms to themselves and others. A "voluntaristic" approach, however, suggests the user is capable of weighing risks and benefits to make responsible decisions about consumption. Recognizing that the majority of users do not want to be ‘cured’ of their drug use so much as continue to use without adverse consequences, users’ own perceptions of controlled use and the potential for abuse is an important distinction for effective intervention. Such an approach underscores the potential for controlled drug use while still stopping short of its active promotion.

Perceptions of users are known to reflect a hierarchy of risk wherein cannabis is considered least harmful of all illicit drugs (and alcohol)—not an unrealistic assessment despite its variance with their largely undifferentiated legal status. A voluntaristic view of drug use is indeed most compelling for cannabis given its apparently benign status in the current scope of public health priorities. Moreover this view has clear implications for research on cannabis as well as the ongoing legal policy debate. A false antithesis exists between those who argue cannabis is harmless and those who maintain that it carries significant risk and the corresponding policy recommendations of these positions. A balanced assessment requires recognition of both costs and benefits of cannabis use and of prohibition outcomes respectively.

Research is scarce that examines both sides of the issue, examining correlates of problematic, or chronic, use patterns as well as more adaptive and functional patterns of consumption. The question of dependency and other problems in this schema are as inseparable from the analysis of physical and psychological effects of the drug as they are from the context and circumstances, or set and setting, in which users weigh the costs and benefits of use. The present aim is to fill in gaps in knowledge by establishing motivations for cannabis use and its effects, including dependency and other adverse consequences, as reported by 104 experienced users in Toronto, Canada.



Study participants were recruited through a classified ad in a local free wide-circulation newspaper seeking ‘experienced’ cannabis users, 18 years or older, with 25 or more times lifetime use. Approximately 200 persons left telephone messages expressing interest in the study, nearly three quarters of whom were successfully contacted and willing to take part in a face-to-face private interview at the research office of the investigator. One hundred and four kept their designated appointments, consenting to participate on conditions of strict confidentiality and that all information gathered would be used for public health purposes only. Interviews were conducted between October 2000 and April 2001.

The final sample comprises 64 male and 40 female respondents between 18 and 55 years of age (mean 34 yrs.), over three-quarters (77%) of whom used the drug at least weekly in the month prior to interview. Weekly use was reported by 80% and 81% of them in the past 12 months and 3 months, respectively. Close to half had used cannabis daily in the past year, 3 months, and 30 days (51%, 47%, and 47%, respectively) prior to interview. Eighty-one percent report using cannabis daily during their period of heaviest use. Nearly half of the sample (49%) had used one ounce (28 grams) or more per month on average during this same period. Close to a quarter of the respondents (25%, 23%, and 20%) report use at this high level in the past year, 3 months, and 30 days, respectively.

Despite its non-random design limitations, respondent self-selection, or ‘convenience sampling,’ was deemed advantageous as a cost-effective method of attracting more long-term, heavy frequent users to the study. This subgroup of users is most relevant in terms of public health policy research and dependency concerns around cannabis. Further to the nature of sampling bias, respondents were paid C$25 to participate in the study. Thus, although many became involved due in part to their interest in this research, the provided cash inducement may well have impacted the socioeconomic distribution of the sample.

Indeed, it is noteworthy that 82% of respondents averaged less than C$2000 a month (net income) in the previous tax year, and 36% earned less than half that modest income. While only 41% of respondents were fully employed (35 or more hours per week), 12% were full-time students, and nearly a quarter (24%) were on some form of public assistance—nearly half of the latter group (10% of the sample) received Disability payments. Thus on the whole, though by no means exclusively, the sample likely over-represents underemployed, low-income cannabis users.

An in-depth questionnaire covering cannabis use patterns, effects, consequences, and problems was administered in face-to-face private interviews. In order to target specific advantages and disadvantages of use, several standardized lists of potential drug effects were presented to respondents as a way to measure and rank the prevalence of both negative and positive cannabis use outcomes. Adapted as they were from previous studies of illicit drug users, these lists have been extensively piloted and used for similar research purposes elsewhere.,,

Cannabis dependence was assessed using questions adapted from DSM-IV criteria. Briefly, respondents were asked questions relating to amounts used and time spent using; continued use despite social, psychological or physical health problems attributed to cannabis use; and whether cannabis use had ever led to neglect of social, recreational, home, school or work activities. In addition, interviewees were specifically asked about the prevalence of these problems in the 12 months prior to interview. Additional operationalizations of the concept ‘dependence’ tapped the drug’s overall importance and impact on the daily lives of users. These indicators included reports of deviant or criminal behaviour to obtain (money to buy) cannabis, recurring legal problems and other problems attributed to cannabis, and having ever sought out or considered treatment or counselling for cannabis-related problems.



To gain a balanced view of advantages and disadvantages, a voluntaristic, or ‘rational choice,’ view of drug use suggests perceived benefits of use are key determinants behind its persistence (if not always its initiation). Drug use benefits are weighed against its untoward consequences and, all things being equal, presumably weigh in favour of continued use. Attention is thus duly paid to the perceived benefits, as well as costs of using, in an effort to establish people’s motivations to use cannabis. Respondents were first presented with a list of 20 possible reasons for using cannabis and for each reason asked to indicate its importance to them personally. Relaxation is seen as the most important reason for cannabis use, and the most prevalent reasons are predominantly recreational in nature.

Twelve of the 20 reasons score higher than neutral on average. Combining the categories ‘important’ and ‘very important,’ the five top reasons in order of importance are ‘to relax’ (89%), ‘to feel good’ (81%), ‘to enjoy music, movies, or TV’ (72%), ‘as a cure for boredom’ (64%), and ‘to get inspiration’ (60%). The next four reasons (deemed at least ‘important’ by more than half the sample)—‘to blow off steam’ (61%), ‘to feel less anxious,’ ‘to see the world with fresh eyes,’ and ‘to forget your worries’ (all 55%)—are noteworthy for they loosely connote the use of cannabis as a coping mechanism. Its use as a ‘social lubricant’ comes still further down the list (behind ‘to cope with depression’ and as an aid ‘to help you sleep’), suggesting that marijuana’s reputation as a social drug has been by and large overstated.


Costs and benefits of using cannabis

In addition to the reasons people give for using cannabis, insight on specific use effects is needed to obtain a balanced view of costs and benefits. To gain a better understanding of both positive and negative use aspects, extensive standard lists of potential drug effects were presented. Respondents were asked if they experienced each of 28 effects never, seldom, sometimes, often, or always after using cannabis. Fourteen effects were experienced more consistently than ‘sometimes,’ and most are unequivocally positive. Seven of these are reported ‘always’ or ‘often’ by more than half the sample. According to the majority, "using cannabis makes me feel…": ‘relaxed’ (95%), ‘comfortable’ (86%), ‘merry’ (69%), ‘optimistic’ (68%), ‘attentive to aesthetics’ (64%), ‘intuitive’ (53%), and ‘talkative’ (52%). By contrast, the least frequently listed effects—e.g., ‘mentally weak’ (3%), ‘pessimistic’ (5%), and ‘paranoid’ (7%)—are decidedly negative attributes.

To examine more direct effects of using cannabis, respondents were asked about 53 possible drug effects. For each they were asked if they had ever experienced that effect when using cannabis and, if so, had it occurred one to five times or more than five times. The arbitrary cut-off of more than five times is meant to diminish the probability of chance effects such as, for example, using cannabis that has been mixed with other substances. Whereas the use of this cut-off is questionable when dealing with experienced users, most of whom have used cannabis many hundreds (even thousands) of times, it still acts to differentiate expected effects from more spurious use outcomes.

Focusing on the most prevalent items (the 15 effects experienced more than five times by over half the sample), the data are more equivocal than those above as to the predominance of positive effects. Perceived benefits of using cannabis—e.g., ‘having a sense of well-being or euphoria’ (85%), ‘forgetting worries’ (65%), ‘feeling energetic’ and ‘higher self-confidence’ (both 64%), and ‘clear thinking’ (56%)—once again rank highly. Certain negative use aspects, however, such as ‘dry mouth’ (79%), ‘absent-mindedness’ (62%), ‘forgetfulness’ (60%), and ‘loss of motivation’ (53%) also figure prominently. Other highly ranked effects—i.e., ‘talkativeness’ and ‘bouts of laughter’ (both 77%), ‘mind wandering’ (74%), ‘sexual stimulation’ (54%), and ‘thinking faster’ (52%)—are neither clearly negative or positive, but seem rather more contingent on the intent and circumstances of use. By contrast, negative drug effects that are sometimes associated with other types of drug use such as ‘convulsions,’ ‘unconsciousness,’ and ‘violent behaviour’ are rarely experienced, if at all, by cannabis users.

These data show that cannabis users attribute a wide variety of effects to their drug of choice. While the direct effects of cannabis are by no means always advantageous, its positive aspects tend to figure more prominently in user experience. Responses of the middle range (such as ‘feeling separated from your body or environment’ and ‘lacking ambition,’ for example) suggest certain effects that are relevant to many users do not occur at all for many others. Other more ambiguous effects, such as ‘mind wandering,’ may be relevant (and thus more clearly positive or negative) to some, but only in light of the setting and circumstances.

To isolate negative health effects of using cannabis, respondents were presented with a list of 23 physical symptoms. For each they were asked, had they ever experienced that symptom and, if so, did they think it was related to their use of cannabis. Of this list of physical effects ‘extra appetite for food’ (83%) was by far the most frequent effect attributed to using cannabis. Other frequent symptoms (reported by one third or more of respondents) were ‘restlessness’ (55%), ‘anxiety’ (50%), ‘respiratory problems’ (48%), ‘feeling physically unfit’ (45%), ‘insomnia’ (43%), and ‘throat problems’ (33%). Unlike extra appetite, however, most such symptoms were attributed to cannabis by only about half of those who had ever experienced them.

Contrarily, by some (with regard to anxiety and insomnia, for example) the drug was credited instead with relieving the reported symptom. Indeed, of the latter group of symptoms, only ‘throat problems’ are attributed to cannabis by a large majority (79%) of those who report them. With regard to throat and respiratory problems, the high prevalence of tobacco smoking in the sample is undoubtedly a confounding factor. Nearly three quarters of respondents report use of tobacco in the 3 months prior to interview and over 1000 times lifetime prevalence (73% and 74%, respectively). Over two thirds (69%) report using tobacco with cannabis at least ‘sometimes.’ The frequent attribution of these problems as being due to—or at least exacerbated by—smoking cannabis by those who ever experienced them (56% for ‘respiratory problems’), however, is nonetheless noteworthy in terms of fixing public health priorities in a way that is meaningful for heavy users.

Despite the occurrence of cannabis-related health problems perceived by some, the vast majority of respondents (89%) were certain they would use cannabis again in the future and over half of them (55%) indicated they would never stop using altogether (another 21% remained uncertain). When asked about the drug’s importance to their overall style of life (i.e., what difference would it make if they couldn’t get it or use it anymore?), over three-quarters considered it ‘somewhat important’ (48%) or ‘very important’ (31%). Compared to other activities that may fulfil similar functions, the advantages attributed to using cannabis made it nonetheless unique in the eyes of the majority (59%). This profound conviction regarding its benefits and commitment to continue using cannabis indefinitely by more than half the sample is further illustrated by its perceived long-term effects.

Respondents were asked to indicate their level of agreement on each of 18 items about the drug and its impact on their lives in general. Whereas none of these items came close to ‘agree strongly’ on average, of the 7 that rank lower than neutral (i.e., were agreed to by more than half the sample) all are distinctly positive attributes. Combining ‘agree’ and ‘agree strongly’ as one category, for example, respondents indicated "As a result of using marijuana, I…": ‘have more fun in life’ (83%), ‘have come to know myself better’ (77%), ‘am more open to other people’ (73%), ‘have more appreciation for beautiful things’ (69%), ‘have become more balanced,’ and ‘am happier with myself’ (both 60%). By contrast, the least agreed with items are mostly negative—e.g., I am…‘less efficient’ (26%), ‘less productive,’ ‘slower thinking’ (both 29%), and ‘less ambitious’ (30%).


Dependency criteria

Notwithstanding the predominance of positive over negative effects, a balanced assessment of benefits and costs of using cannabis must acknowledge the occurrence of the latter, as do a sizeable minority of users in the present sample. Additional costs are entailed, and with them curtailment of benefits, to the extent that dependence may distort users’ perceptions of the precarious balance between positive and negative drug effects. Although use of the concept ‘dependence’ (particularly with cannabis) inherits many difficulties and ongoing disputes among experts, a number of indicators now in standard usage offer a provisional basis on which to examine the problem. Given the importance of cannabis in the daily lives of users (and limited financial resources of many in the present sample), a reasonable reflection of dependence is in the prevalence of special or deviant activities enacted to obtain the drug.

Respondents were asked had they ever engaged in each of 12 such activities specifically in order to obtain cannabis and, if so, how many times. Of all listed activities, only five were affirmed by more than a handful of respondents. Most (62%) report having been in an uncomfortable situation or hanging around people they did not like (at least once or twice) in order to get cannabis. Other frequent activities include borrowing money, selling cannabis to support their own use of the drug, and taking on extra work to buy cannabis. Of these activities, only selling cannabis is unlawful per se, a noteworthy transgression given its frequency of more than 10 times by one in four respondents (24%). More serious crimes, however, such as theft and prostitution to obtain money for cannabis occur only rarely, if at all.

Correspondingly, only 6% of the sample ever had ‘recurring legal problems’ due to their use of cannabis. This figure drops to 1% for the 12 months prior to interview. The frequency of other types of problems is another relevant indicator. Respondents were asked did cannabis use ever cause problems at school or at work, in public places or in their interpersonal relationships and, if so, did it cause serious or only minor problems. Nearly half of them (46%) report (at least minor) problems with cannabis in family or personal relationships. A third of the sample (34%) had experienced such problems at school, and 29% report mostly minor problems in public places like bars, concerts, or on the street. Work-related problems due to cannabis are less common, with 22% of respondents having experienced minor or more serious problems.

In addition to deviant behaviours and problems associated with using cannabis, dependence may be indicated by the prevalence of a strong subjective desire, or ‘craving,’ for the substance. Having ever had such cravings was affirmed by more than three quarters (77%) of respondents, most of whom (47% of the sample) had been had been using the drug for two years or longer before they found themselves craving it. Far fewer respondents (34%) have ever felt ‘obsessed’ with using cannabis, however. A large majority of this sample (88%) moreover affirms that they have their use ‘under control.’ To further explore the prevalence of ‘cannabis dependency’ in the sample, a more standard set of criteria is derived from the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

DSM-IV firstly distinguishes between substance dependence with physiological dependence (i.e., evidence of tolerance or withdrawal) and substance dependence without physiological dependence (i.e., no evidence of tolerance or withdrawal). Because withdrawal is not a criterion associated with cannabis in DSM-IV and tolerance has an ambiguous status, in that it may or may not develop in cannabis users, withdrawal and tolerance were left out of the list of dependence criteria derived for use in this study. With these adaptations in mind, DSM-IV defines non-physiological ‘substance dependence’ as a maladaptive pattern of substance use, leading to clinically significant impairment or distress, as manifested by three (or more) of the following, occurring at any time in the same 12-month period:

1. The substance is often taken in larger amounts or over a longer period than was intended.

2. There is a persistent desire or unsuccessful efforts to cut down or control the substance use.

3. A great deal of time is spent in activities necessary to obtain the substance, use the substance, or recover from its effects.

4. Important social, occupational, or recreational activities are given up or reduced because of substance use.

5. The substance use is continued despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by the substance.


Unlike DSM-IV, which targets the confluence of criteria occurring in the same 12-month period, the derived list of questions examines criteria occurring at any time in the respondent’s use experience. In so doing, the sensitivity of the DSM-IV defined criteria is increased, while longitudinal use pattern differences between users are discarded in favour of a more general view on the overall prevalence of these items. In addition, to assess the continuation or cessation of dependency problems in more recent and current use, last 12 months prevalence of reported problems is asked separately. The survey instrument included six questions based on the above DSM-IV criteria. The results are reported below.

Thirty percent of respondents report a lifetime prevalence of three or more of these criteria. This figure reduces to 15% for the 12-month period prior to interview. Thus overall, and for the latter four items specifically, dependency criteria decline markedly (by half) between ‘ever experienced’ and past year prevalence. Perceived problems with the use of cannabis per se (i.e., the frequency or amounts used as opposed to its impact on users) are shown to diminish less dramatically (by approximately one third). Interestingly, however, no significant correlation was found between the frequency of cannabis use, during heaviest use period and last 12 months respectively, and the number of reported DSM-IV items. Similarly, there is no correlation between average monthly consumption in grams for these periods and the above dependency criteria.

To determine what proportion of the sample had sought formal help for dependency problems, respondents were asked if they had asked about or received treatment or counselling for a drug or alcohol problem in the last two years. Fourteen percent responded affirmatively, though only one third of them (5% of the sample) had done so in connection with their use of cannabis. Reported substance use problems were more prevalent for alcohol and cocaine (7% and 6%, respectively) and less so for heroin and ‘others’ including prescription drugs (2% for each).

An additional 14% of the sample affirmed that they had ‘ever thought’ about getting treatment or counselling specifically for cannabis. It is noteworthy that nearly three quarters (71%) of those who had ever considered seeking formal help for cannabis dependency report using an ounce or more per month on average during their heaviest period of use. Moreover, all of them were daily users during this period. In the 30 days prior to interview, however, close to half of those who had thought about treatment for cannabis (6% of the sample) had stopped daily use, and less than one quarter (21%) continued to use at the ounce-or-more per month level. Fourteen percent of this group had not used cannabis at all in the past month.



These data support a ‘rational choice’ view of drug use in which users are capable of weighing costs and benefits of cannabis and making decisions about continued use in light of this rational calculus. Based on a convenience sample of 104 experienced, mostly long-term frequent users, the results of this study indicate the predominance of positive over negative consequences which in part explains the ongoing popularity of the drug today. Not surprisingly, the most prevalent reasons to use cannabis tend to favour recreational enjoyment, encompassing relaxation and enhancement of leisure activities. However, its related use as a coping mechanism in times of stress and anxiety also figures prominently—especially when compared to its more widely acknowledged and appreciated role as a social lubricant, for example.

When presented with extensive standard lists of common drug effects, cannabis users tend to rank unequivocally positive effects over more ambiguous and negative use outcomes. Unequivocally negative physical and behavioural effects sometimes associated with more dangerous drugs such as alcohol (unconsciousness and violent episodes, for example) are rarely, if ever, experienced. Respondents’ evaluations of more ambiguous effects seem contingent on circumstantial ‘set and setting’ factors. To illustrate, whereas ‘bouts of laughter,’ ‘mind wandering,’ and ‘sexual stimulation,’ may be sought after effects among intimates, these are likely best avoided in other types of company. Further, many effects that are relevant to some do not occur at all for other users.

Analysis of negative health effects showed extra appetite for food is by far the most common physical symptom attributed to the use of cannabis. Circumstantial ambiguities arise here again, however, as increased appetite may well be a positive effect in the context of medicinal use for some and leisure-time consumption for others. Other commonly reported symptoms (such as insomnia and anxiety) are relieved by, as well as attributed to, the use of cannabis. Less trivial, however, in terms of public health priorities, over a quarter of respondents report respiratory and throat problems caused (or at least exacerbated in concomitant use with tobacco) by their use of cannabis.

A harm reduction approach recommends public educational attempts to diminish customary practices such as deep inhalation and breath holding (which facilitates the deposition of particles without markedly increasing THC delivery), and the concurrent use of tobacco and cannabis by combustion. Because THC is a bronchodilator, it may augment the deleterious impact of tobacco smoking by abetting the deposition of particles deeper into respiratory airways. Similarly, development of smokeless delivery through cannabis beverages, lozenges, or the use of ‘vaporizers,’ for example, should be encouraged to diminish pulmonary hazards.

Perceiving that both the short and longer-term benefits of using cannabis outweigh any negative consequences, a clear majority of respondents indicated a commitment to continue using into the foreseeable future. Despite acknowledged difficulties with the concept of cannabis ‘dependence,’ analysis of indicators based on DSM-IV among other substance use problem criteria was conducted. Whereas their use of the drug was deemed ‘very important’ by nearly a third of the sample, the absence of serious crimes or other deviant behaviour enacted to procure cannabis is noteworthy. Less than one in fifteen report recurring legal problems due to their use of cannabis, although a quarter of those interviewed had sold the drug on more than ten occasions. In order of frequency, lifetime prevalence of problems with cannabis in family or personal relationships, at school, in public places, and at work are reported by a minority of users.

Likewise, less than half of respondents report ever ‘craving’ cannabis. A large majority, by contrast, claim to have their use under control. To provide a more sensitive and ‘objective’ measure of cannabis dependence, DSM-IV standard criteria for non-physiological dependence were adapted for use in the study. Affirmative responses on each of six problem indicators range from less than one fifth to one half of the sample. The proportions of all indicators representing cannabis use-related difficulties drop dramatically (by approximately one half) for the 12-month period prior to interview. By contrast perceived past-year problems related to amounts or frequency of cannabis use per se, and the desire or failed attempts to cut down, diminish less markedly over previous levels, remaining on the order of one third and one quarter of respondents, respectively.

In light of this finding, the most frequently encountered problems with cannabis have more to do with self-perceptions of excessive use levels than with the drug’s perceived impact on health, social obligations and relationships, or other activities. Lending support to the highly subjective nature of this evaluative process, no significant correlations were found between amounts nor frequency of use and the number of reported DSM-IV items. For those for whom cannabis dependency problems progress to the point of seeking out or considering formal help, however, the substantive significance of perceived excessive use levels cannot be overlooked.

Of the small minority of the sample who had ever thought about getting treatment or counselling for their use of cannabis—all prior daily users—only about half were using daily when interviewed. Likewise, although most of them were one-time ‘heavy’ users (one ounce or more per month), the majority had ceased to use at this high level. Thus despite the lack of a clear and consistent relationship between frequency or amounts of cannabis use per se and dependency problems, users still (re)evaluate costs and benefits in light of use levels and adjust their intake accordingly. The reflexivity of this self-control process is important given the predominance of long-term heavy, frequent users in the study. Future research employing larger representative samples of experienced users is needed to examine and more fully comprehend the complex interplay between cannabis use and its consequences at variant use levels. Adequate measures to enhance population health must be based on a fuller picture of the distribution of adverse effects, as well as positive aspects, experienced across the spectrum of cannabis use patterns in the overall population.


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