Cannabis andharmreduction

ISSN 09595235 printISSN 14653370 online0001010112 copy Australian Professional Society on Alcohol and Other Drugs

Drug and Alcohol Review (2000) 19 101112

Wendy Swift PhD Senior Research Assistant Jan Copeland PhD Lecturer National Drug and Alcohol Research Centre University of NewSouth Wales Sydney New South Wales 2052 Australia Simon Lenton MPsych(Clin) BPsych Research Fellow National Drug ResearchInstitute Curtin University of Technology GPO Box U1987 Perth Western Australia Correspondence to Simon Lenton

Note from the EditorAlthough cannabis is the most widely consumed illicit drug in many western countries there is a paucity of information about harm reduction strategies forthis drug In part this may be due to the polarized debate around cannabis which tends to characterize it as wholly evil or wholly good In this paper WendySwift Jan Copeland and myself attempt to summarize the major health harms from cannabis use the harms associated with the application of the law tocannabis use and offer some harm-reduction strategies The special case of cannabis use by adolescents is also discussed

SIMON LENTON

HARM REDUCTION DIGEST 8

Cannabis and harm reductionWENDY SWIFT1 JAN COPELAND1 amp SIMON LENTON2

1National Drug and Alcohol Research Centre University of New South WalesSydney amp 2National Drug Research Institute Curtin University of Technology PerthAustralia

Introduction

Cannabis is typically used experimentally or inter-mittently in adolescence and early adulthood and isgenerally discontinued by the mid- to late 20s [12]While only a minority proceed to long-term regularuse it is by far the most widely consumed illicit drugin many western countries [3] Approximately 40 ofAustralians aged 14 years and over have tried cannabisand almost one in five (18) have used it in the pastyear [4] Survey data indicate that the lifetimeprevalence of cannabis use in Australia and the UnitedStates particularly among adolescents has increasedthroughout the 1990s after a decline in the 1980s andearly 1990s [48] In Australia the prevalence oflifetime and recent use among female adolescentsappears to have almost doubled between 1995 and1998 [4]

Shortly prior to the 1937 ban on its use a vigorouscampaign was launched by the US Federal Bureau ofNarcotics which portrayed cannabis as a potentnarcotic inextricably linked to deviant behaviourmdashReefer madness led to violent crime heroin addiction

and social menace While this view is generallyconsidered extreme today there is a major schism inthe perception of cannabis with polarized viewsexpressed by vocal opponents Proponents of its useargue that it is a natural relatively harmless drug withmany beneficial properties its image tarnished by liesand myths [eg 910] Others claim that the harms ofcannabis have been understated and that it is a toxicdrug that causes widespread harm [eg 1112]

Cannabis is illegal in most jurisdictions in Australia(and many other countries) although the possession ofsmall quantities has been decriminalized in some statesand territories and there are trials of a range of legaloptions for low range offences Since 1985 Australia sofficial policy on cannabis and other drugs has beenone of harm reduction There is a spirited debate inAustralia and elsewhere about cannabis-related harmPoints of contention include claimed increases in thepotency of cannabis [eg 13] what legislative respon-ses should apply to its possession use and cultivationits use as a therapeutic agent for a variety of medical

102 Wendy Swift et al

conditions and the most appropriate responses toadolescent use (eg school expulsions)

There is also controversy about the definition andscope of harm reduction (HR) Lenton amp Sin-gle [14] in the opening contribution to this Digestseries made a distinction between HR as a broadpolicy goal and HR as a strategy They provided thefollowing practical criteria for assessing whether apolicy or programme practices HR First the centraldefining characteristic of HR is a focus on thereduction of harm as a primary goal rather than thereduction of use per se it must include strategies forthose that continue to use as well as those aimed atreduction of use or abstinence and there should besome attempt to evaluate whether these strategies willprobably result in a net reduction in drug-relatedharm [14 p213] It is important to note that HR isnot antithetical to abstinence-orientated programmesand supply reduction strategies This Digest willaccordingly cast a fairly wide net and cover issuesrelated to reductioncessation of use and reduction ofharms

Cannabis and harm reduction

This article aims to use a fairly broad approach toHR issues for a variety of reasons First the abilityto make causal inferences about the harms associatedwith chronic use in particular is hampered by a lackof longitudinal research and delays in the manifesta-tion of some adverse health and other effects anddifficulties in ruling out alternative explanations whensuch delays occur While HR for cannabis iscurrently being promoted and practiced by many inthe substance use field discussion of the issue iscontroversial Some people consider HR tacitapproval of illicit drug use or as synonymous withcalls for drug law reform More specifically forcannabis the emotive and often irrational policydebate is a major obstacle to the evaluation andrealistic reduction of cannabis-related harm partic-ularly when the type and extent of harms aredisputed The maximization and minimization ofharms by opposing camps in this debate com-promises the provision of a consistent believablemessage measurement of the costs and benefits ofHR initiatives and the evaluation of policyimpact [1517]

Having said that there is enough reason to beconcerned about the probable harms that some peoplemay encounter when using cannabis to promote

discussion and awareness of HR Cannabis would beunlike all other psychoactive drugs if it was completelybenign As described below there is research toindicate that when used in particular ways or bycertain people cannabis is associated with a variety ofadverse health and other (eg social employment)outcomes These harms may be caused more directlyby cannabis itself (eg health) or stem from currentpolicies on cannabis use (eg legal) They may have arange of impacts from an individual to the communitylevel For the sake of brevity only some of these harmsand associated HR strategies are outlined below andissues considered to be of particular interest arehighlighted It should be stressed that the followingdiscussion is not an argument for a particularlegislative or policy position

Health-related harm

Acute administration of cannabis has effects on avariety of bodily systems although these do notnecessarily disrupt functioning or predict the long-term effects of cannabis use For example while acuteadministration of small doses of cannabis producesbronchodilation chronic use may produce obstructiveairways disease [18] The risk of experiencing severetoxic effects is limited by the aversive psychotropiceffects produced by the high doses required Thistypically leads to the cessation of use before the onsetof dangerous symptoms [19] However the effects ofcannabis are variable and may also be mediated byfactors other than dose including method of use drugexperience tolerance concurrent drug use expecta-tions and personality [20]

Cannabis has a very low acute toxicity [21] and isonly a minor contributor to drug-related mortal-ity [2224] Its major public health significanceresides in its association with morbidity [15] Thepublic health significance of these outcomes is affectednot only by their severity but by the prevalence ofcannabis use As most cannabis use is experimentaland intermittent and the patterns of use producinglong-term outcomes relatively rare the greatest numberof people will experience the acute negativeeffects [15] However in terms of the relative like-lihood of experiencing the adverse health consequencesof use the major health risks are more likely to beexperienced among regular long-term users [25] Onthe basis of current use patterns it has been estimatedthat cannabis produces only small to moderate public

Harm Reduction Digest 8 103

health risks and makes only a small contribution to theglobal burden of disease compared with the mostprevalent drugs alcohol and tobacco [152526]

Despite this comparatively smaller public healthburden as the most prevalent illicit drug cannabis hasthe potential to cause distress and a number ofpotentially serious adverse consequences to a largenumber of people particularly those who persist intheir use over many years Recent authoritative reviewsemploying explicit evidential standards have summa-rized the major probable health effects of acute andchronic cannabis use based on the available evi-dence [eg 19 27 28] These are summarizedbelow

Probable acute harms

The most probable adverse health effects of acute usewhich are generally self-limiting and do not persistbeyond intoxication are

Ÿ negative psychological effects such as anxietydysphoria panic and paranoia These effects may beparticularly pronounced in naive users and contrib-ute to the occurrence of panic attacks

Ÿ disruption of cognitive function (eg memorylearning and temporal processing) and psychomo-tor impairment [2930] Cannabis use could beviewed as potentially disruptive of everyday behav-iours reliant on complex cognitive processingPsychomotor impairment may also increase the riskof accidents while driving or operating machineryWhile cannabis is the second most frequentlydetected drug in road accidents after alcohol [31]its causal role in these events is debated Forexample in comparison to the risky behavioursinduced by alcohol consumption those intoxicatedby cannabis alone may recognize their impairmentand attempt to compensate by driving more slowlyrefraining from overtaking and focusing attentionon anticipated tasks Nevertheless such compensa-tions may be offset by the occurrence of unexpectedevents lack of control of the surroundings or whensustained attention is required [see 202930] Can-nabis and alcohol which are frequently usedtogether may be additive in their effects onpsychomotor impairment and driving perform-ance [32] Thus cannabis may amplify alcohol-induced impairments and

Ÿ an increased risk of experiencing psychotic symp-toms among vulnerable individuals [33]

Probable chronic harms

In addition the most probable effects of regular (daily ornear daily) sustained use (over several years) are

Ÿ a cannabis dependence syndrome characterized bya variety of cognitive physical and behaviouralsymptoms such as an inability to control usecontinued use despite problems withdrawal andtolerance [eg see 34] The chronic use patternsassociated with dependence may be resistant tochange increasing the likelihood of experiencingother adverse outcomes Cannabis dependence hasthe potential to create significant costs in terms ofprovision of treatment services for those who wishto stop and reduced work or educational perform-ance Further the experience of dependence may bedistressing quite apart from other more obviousadverse experiences and may interfere with normaldaily functioning and the enjoyment of life

Ÿ subtle cognitive impairment affecting attentionmemory and the organization and integration ofcomplex information At present these impairmentsdo not appear to be grossly debilitating and theirreversibility is unknown [35]

Ÿ adverse respiratory effects such as chronic bronchi-tis and histopathological changes which may beprecursors to cancer [36] Route of administrationis obviously a major mediator of this risk withsmoking the almost universal mode of use InAustralia waterpipes (mdashbongs ) are the most fre-quently used smoking device particularly amongyounger users [13] Cannabis and tobacco smokecontain many carcinogenic compounds and respira-tory irritants [3738] Research suggests that water-pipes may deliver greater concentrations of tarpartly because the smoke is inhaled more deeplyand held for longer [39] In addition manysmokers mix cannabis with tobacco and are regulartobacco smokers There is evidence that some of thenegative respiratory effects of cannabis and tobaccomay be additive [36]

High-risk groups

Certain groups may be at a higher risk of developingthe adverse acute and chronic effects of cannabis [see192728] These include

Ÿ adolescents (this issue is discussed below)Ÿ pregnant women continued smoking throughout

pregnancy may increase the risk of having a lowbirth weight baby


Ÿ those with respiratory or cardiovascular diseasewhose conditions may be aggravated by use

Ÿ those with a co-morbid disorder the co-occurrenceof two or more substance use disorders (egcannabis and alcohol use disorders) or substanceuse and other mental health disorders (eg sub-stance use disorders and anxiety or depression) isrelatively common [40] In general those with co-morbid disorders have been shown to experiencegreater disability and poorer outcomes than thosewith a single disorder [eg 4041] Those withschizophrenia may be particularly susceptible to theeffects of cannabis There is evidence that use mayexacerbate psychotic symptoms in those with thedisorder and long-term heavy use may precipitateschizophrenia in vulnerable individuals [33]

Health-related harm reduction

There are a number of strategies aimed at reducing theharms associated with the adverse health outcomeslisted above Some may be more orientated toreduction or cessation of use while others target thereduction of specific harms without necessarily entail-ing major changes in frequency or quantity of useHarm reduction tips have been produced in manyformats and from such diverse sources as drug andalcohol and generalist health services user groupsDutch mdashcoffee shops and the police service

While a key challenge is to develop appropriatemessages in acceptable media for relevant targetgroups some broad HR tips pertinent for the probableharms cited above are listed below The most obviousadvice in order to avoid harm is not to smokeHowever this is not necessarily acceptable or desirableto many users who may simply wish to minimize therisk associated with use It is important not tounderestimate the benefits cannabis use is perceived toprovide (eg relaxationmdashtime out ) which may bepowerful motivators for continued use despite thesimultaneous recognition of cannabis-related prob-lems Some users perceive cannabis use to be a form ofharm reduction in itself because they believe that itcreates less problems for them than other drugs suchas alcohol [4243]

First as with other drugs information is the firstweapon against harm It is well known that knowledgedoes not necessarily ensure behaviour change How-ever the provision of accurate and empirically basednon-sensational timely and acceptable information onthe probable risks associated with short- and long-term

cannabis use is a vital aid for users making informeddecisions about whether or how to use cannabis andwhen use might be becoming a problem

Adverse psychological effects If users are prone toexperiencing anxiety paranoia and panic when smok-ing the best advice is not to use For those who chooseto continue smoking setting limits on the amountsmoked not mixing cannabis with drugs that couldheighten such feelings and smoking in a safeenvironment with trusted friends who can providereassurance may limit their occurrence or the severityof their effects It is important for users to be awarethat for most such unpleasant feelings will pass Thosewho are schizophrenic or are prone to psychoticsymptoms need to be aware of the possibility ofexacerbating such symptoms or precipitating a schizo-phrenic episode While limiting use may alleviateminor psychological discomfort in most users in thisgroup abstinence is the most advisable HR measuredue to the serious and distressing nature ofsymptoms

Psychomotor impairment While the extent to whichcannabis is implicated in accidents is debated anypsychomotor impairment may decrease the likelihoodof coping successfully in an unexpected situation oremergency putting the user and others at risk Againusers should be advised not to smoke before driving avehicle or operating machinery especially if the task isunfamiliar or requires sustained attention In partic-ular they should be advised against mixing cannabisand alcohol in this context Users should also be awareof the potential of experiencing a mdashhangover themorning after a heavy smoking session

A controversial strategy aimed at reducing poten-tial harms arising from drug-related impairment andincreasing work-place productivity is drug testingThis policy has been criticized by some commenta-tors [eg 44] who argue that it measures drugexposure rather than actual impairment there is littlebaseline information on the prevalence of substanceuse and substance-related impairment in the work-place on which to base its application and littleevidence that drug testing actually increases safety orproductivity Given the retention of cannabis in bodytissue for up to several weeks such testing is not anaccurate reflection of use recency or impairmentWhile such programmes may provide benefits byacting as a deterrent to drug use for some [44] thesemust be traded against potential social costs (eg lossof employment) which may be consequent totesting


Respiratory harm The risk of spreading infectiousdisease such as influenza can be decreased by notsharing joints and bongs and cleaning smokingequipment regularly Eating cannabis or drinkingcannabis tea will eliminate smoking-related harmsThis recommendation may not be readily acceptedbecause it is difficult to titrate the dose whenconsumed orally and patience is required for the onsetof effects which are less predictable than whensmoked [2045] As most users prefer smoking harmmay be reduced by avoiding mixing with tobaccosmoking joints rather than waterpipes and avoidinginhaling deeply Vaporizers which heat (rather thanburn) the cannabis and trap toxins inside theapparatus are a potentially viable alternative to themost commonly used smoking devices However ithas been suggested that they may not be as efficient atdelivering THC as other smoking routes and thatusers may need to ingest more smoke to achieve thedesired intoxication [46] It has also been suggestedthat smoking higher-potency cannabis may reduce theamount of smoke inhaled because users would becomeintoxicated more quickly [eg 46] There is mixedevidence that cannabis users are able to titrate theamount of THC by varying their smoking techni-que [eg 4748] The health effects of an increase inTHC potency are unknown however it is possiblethat any potential respiratory benefits of this techniquemay be offset by an increase in adverse effects (egpsychological effects) [13]

Cognitive impairment The impairment associatedwith chronic use may be very subtle and not easilyextrapolated into everyday situations However impair-ments of attention and memory suggest that if users areconcerned about the impact of regular smoking on theirdaily performance and interactions with others theyseek assistance to moderate their use or at least limittheir consumption the night before an important orunfamiliar task Again they should be aware of themdashhangover effects cannabis can produce

Dependence On the basis of epidemiological lit-erature approximately one in 10 people who have evertried the drug meet criteria for dependence This riskincreases with frequency and duration of use withdaily or near-daily users at highest risk of becomingdependent [19] While it is important not to overstatethe risk of developing dependence users need to beaware of this possible consequence of sustainedregular use Cannabis dependence has often beentrivialized as of little clinical relevance and while manyusers can control their use without help [eg 4249]

some experience significant problems and seek pro-fessional assistance to reduce or cease use Usersprefer [49] and need to be aware of a range ofintervention options HR strategies will vary accord-ing to how entrenched use patterns and associatedproblems have become and the goals of the individualconcerned

Self-help materials some of which use a cognitivebehavioural approach have been developed to assist inthis process [eg 50] They may include tips on howto manage withdrawal symptoms removing associatedparaphernalia such as mull tins and bongs monitoringcues to use and planning appropriate alternativeactivities and responses and relapse prevention tipsAlthough plausible none of these materials has beenevaluated independently

There has been little systematic development ofmore comprehensive interventions designed for canna-bis dependence with many being adaptations ofalcohol interventions [eg 5152] Marijuana Anony-mous (MA) is a developing programme in the UnitedStates but has not been established successfully inAustralia Controlled trials of cannabis interventionshave used aversion therapy [53] and supportiveexpressive psychotherapy [54] and as with MA theirefficacy has not been clearly established

A randomized controlled trial of cognitivebehav-ioural therapy (CBT) for cannabis dependence [55]compared group-delivered CBT with a basic skillstraining approach both of which were tailoredspecifically for cannabis dependent clients At 12months follow-up there were substantial reductions innumber of days of cannabis use and cannabisproblems compared with pretreatment but no differ-ences in rates of abstinence (145) between the twotreatment groups Abstinence rates were comparable tothose reported for the alcohol [56] and tobaccosmoking cessation [57] fields This research offers apromising empirically verifiable approach to thetreatment of cannabis dependence and clearly war-rants further investigation

A recently completed Australian randomized con-trolled trial of 229 severely dependent cannabis usersevaluated an individualized CBT approach [58]Participants were assessed and randomized to (a) asix-session intervention package incorporating a moti-vational interview and a standard relapse preventionintervention (b) a one-session version of the moreintensive intervention with a self-help booklet and (c)assessment and placement on a 24-week waiting-listcontrol group


Preliminary findings suggest that while continuousabstinence rates at approximately 8 months were lowthey were consistent with those found in similar studiesof brief interventions for other drugs There was asignificant impact on frequency and amount ofcannabis used and in the associated harms includingrelationships family and work-related issues and onlevels of depression and feelings of dependence

These studies suggest that CBT even brieflyapplied may be an effective approach in the reductionof cannabis use and associated harms among severelydependent users There is considerable scope for thetraining of primary health-care providers in theassessment and treatment of cannabis dependence Aresearch priority is to better understand the process bywhich occasional cannabis use becomes dependencehow best to assist people in the earlier stages ofdependence and how to improve abstinence ratesamong the severely dependent

Legal harm

A range of harms stem from the legislative andcriminal justice systems which aim to prohibit the useof cannabis These harms may be experienced bycannabis-using individuals their families and friendsand the general community The public healthconsequences of the application of the criminal lawagainst cannabis users may be at least as significant asthose that flow directly from cannabis use itself [5961] although as noted above some of the longer-termeffects have yet to be realized Recent researchindicates that most people who receive a criminalconviction for a minor cannabis offence are otherwiselaw-abiding [62] While a conviction can have sig-nificant adverse impacts on employment furtherinvolvement with the criminal justice system relation-ships and accommodation it fails to deter cannabis usein many of those convicted [63] Research has failed toshow that removing criminal penalties for personal usehas led to an increase in the number of regularcannabis users in the general community [6465]

Harms associated with cannabis lawenforcement

Law enforcement-related harms experienced by indi-viduals and the general community include

Ÿ under a total prohibition approach there areconsiderable financial costs related to the applica-tion of police judicial and corrective services

resources to prosecute minor cannabis offences suchas possessionuse minor cultivation offences andparaphernalia offences [6670] In 199697 can-nabis offences constituted about 81 of all drugarrests in Australia [67] Between 70 and 90 ofcannabis offences are minor offences [6268] Thefinancial costs of infringement notice systems havebeen shown to be far less than those associated withstrict prohibition [6970]

Ÿ there may be considerable social costs to individualswho are convicted of minor cannabis offences andacquire a criminal record in terms of impacts onemployment further involvement with the criminaljustice system relationship problems and restric-tions on international travel [617173] Thesecosts are far greater than those experienced by thosereceiving an infringement notice under a systemwhere civil penalties apply [63]

Ÿ there is an overlap of illicit markets for cannabis andother potentially more harmful illicit drugs andsome evidence that when cannabis users go to theexisting illicit market to buy their cannabis they areexposed to a range of other illicit drugs [7374]

Ÿ there are community costs resulting from theinvolvement of criminal elements in the illicitcannabis market There is considerable evidence oforganized crime involvement in large-scale cannabisproduction and distribution in Australia [6768]This brings considerable additional risks to thewider community [677576] including the mdashfairlycommon use of mdashbooby traps armed guards andlarge spring-loaded animal traps to protect sizeableoutdoor crops [67] In South Australia there is someevidence that the previous 10-plant expiation limitwas being exploited by commercial cannabis cultiva-tion enterprises spreading their operations acrosssmaller plantations [77] and

Ÿ recent investigations into police corruption inAustralia have uncovered examples of cannabis-related police corruption which involve largeamounts of cannabis and money [7880]

Legal issues for cannabis users

Many users may be unaware of the consequences of acannabis conviction and wrongly believe they aretrivial Apprehension and court appearance may beseen as an opportunity to make a socio-politicalmdashstatement or voice opposition to the laws (in court forexample) while perhaps not considering the personalramifications


There is evidence that a significant minority ofcannabis users facing legal sanctions are uninformedabout the relevant laws [7381] Laws and associatedpenalties differ across Australian states and territoriesregarding the details of the offences whether civil orcriminal penalties apply use of cautions levels of finesimposed consequences of failing to pay within thespecified period and other procedural factors [82]Additionally there is variability in how cannabis lawsare enforced by police

Avoid coming to the attention of the law Clearly notusing cannabis is the best way to avoid the con-sequences of the law however in some jurisdictionseven being on the premises or owning premises wherecannabis is knowingly being consumed can be acriminal offence [eg 62] There are several common-sense tips for reducing the likelihood of being broughtto the attention of police These include not smokingin public or with strangers Given that a number ofminor cannabis apprehensions are often incidental toother police enquiries [7381] users should be advisedagainst carrying cannabis or smoking utensils onthemselves or in their vehicle and not behaving inways that would otherwise bring themselves to policeattention

The court experience Even in some total prohibitionsystems those charged with minor cannabis offencesmay avoid the public nature of the court process bypleading guilty on the back of a summons and notappearing in court However those that do should beaware that they will still receive a criminal record andbe aware of the consequences of this Less than half ofa sample of Western Australian cannabis offenders thatappeared in court had any legal representation andonly a fifth spoke to a lawyer prior to theirappearance [73] Cannabis users facing court shouldseek and heed legal advice from lawyers court officersor duty counsel and in particular should behave in away which is respectful of the court and its officers

Harm reduction for those convicted of a cannabis offenceThose convicted will need to decide whether to tell aprospective employer about their criminal recordFurthermore cannabis users need to understand thaton efficiency grounds police may decide to morevigorously investigate people who they come in contactwith who are known to have a prior drug history Thismay be the case for prior convictions cautions orcharges not proceeded with that may appear on thepolice record system that can be accessed by police onpatrol Those who receive infringement notices shouldalso know what penalties apply for failing to pay within

the prescribed period Those who are convicted of acannabis offence should know whether they can applyto have the record expunged and after what period oftime

The consequences of having a criminal record mayalso have been magnified by the establishment of thenational and international databases of police intelli-gence In this way cannabis conviction data may nolonger be subject to jurisdictional rules on expunge-ment of convictions and follow the person throughouttheir life as they apply for passports visas andnegotiate other criminal conviction clearanceprocedures

Adolescents

A major focus of concern is cannabis use inadolescence a time of rapid development and transi-tions in life roles While most adolescent use remainsexperimental early onset and adolescent cannabis usehave been related to a number of negative outcomessuch as poor mental health drug use and abusedelinquent behaviour and criminality and poor educa-tional achievement [eg 8387] Recent reviews ofthis literature [eg 38889] have concluded that thereis no simple cause and effect relationship between theextent of cannabis use and other outcomes Ratherthese associations arise because of common or over-lapping risk factors and life pathways between youngpeople who may be predisposed to cannabis use andthose at increased risks of these other outcomes

Epidemiological data have shown that adolescentsmay be significantly more likely to develop cannabisdependence for a given dose than adults [90] A studyof adolescents in treatment for drug use disordersreported that 786 met adult criteria for DSM-III-Rcannabis dependence [91] while 86 of 18-year-oldmales met criteria in a population-based New Zealandlongitudinal study [92]

Research by the NSW Bureau of Crime Statisticsand Research and others shows a strong relationshipbetween frequent cannabis use by juveniles and theirparticipation in crime [9395] Research indicatesthat juveniles resort to income-generating propertycrime to fund their consumption of cannabis and otherdrugs [96] There is a serious gap in the developmentof effective services for young people who use cannabisat problematic levels [97]

Patterns of cannabis use among young people havechanged over the past few decades reflected in adecrease in age of initiation and the preference for the


more potent plant preparations (eg heads) [13] Thesepatterns of use may make continued use and depend-ence an increasingly likely consequence of adolescentcannabis use The paucity of information on correlatesand consequences of cannabis use among adolescentsparticularly its relationship to co-morbid psychopathol-ogy have allowed an ill-informed and polemicalcommunity debate around cannabis to flourish As aresult young people are increasingly sceptical aboutpublic messages on the harms associated with cannabisuse those aged 1419 are more likely to be recentcannabis than tobacco users (346 vs 248) [4]The apparent doubling of reported cannabis use amongadolescent females in the last 3 years [4] has eliminatedthe traditional gender difference in use prevalence Thishas relevance for the development of appropriate drugeducation strategies

While there is a great deal of political pressure forthe widespread implementation of school-based drugeducation the consensus is that such approaches haveno significant outcome on drug-related behaviours orpublic health [9899] Indeed some programmes havebeen shown to increase the likelihood of subsequentsubstance use [100] A project specifically targetingcannabis use has reported some positive effect on self-reported attitudes to cannabis use and future useintentions [101] Drug education models requirerigorous longitudinal evaluation As a recent reviewconcludes school-based programmes should at leastbe based on educational principles rather than drugideology incorporated into many aspects of thecurricula on an ongoing basis and be consistent withthe range of harm reduction objectives [102]

There are no published controlled studies ofinterventions for adolescents with cannabis-relatedproblems As adolescents are not a group that initiatestreatment novel programmes are required A mdashcheck-up style of approach that involves families in a non-confrontational and realistic discussion of the harmsassociated with heavy cannabis use would be worthy ofinvestigation A potential barrier to interventionamong adolescents is their scepticism about drug-related messages generally which may be heightenedby parents who may try and emphasize the risks oralternatively unintentionally model cannabis and otherdrug-use behaviour themselves

Assessing the effectiveness of HR for cannabis

Lenton amp Single [14] note that in practice it is notnecessarily possible to measure the costs and benefits

of HR strategies In reality it may be necessary todemonstrate probable impacts based on similarapproaches or to use surrogate indicators of harmThis may be particularly apt for cannabis whichpresents several practical difficulties for implementingand assessing the impact of HR measures Betterlongitudinal epidemiological data are required toclarify the extent and nature of cannabis-related harmsparticularly those that are subtle andor may take yearsto manifest The illicit unregulated nature of thecannabis industry means that currently little or nocontrols can be enacted to enhance product safety (cfstandard drink labelling reducing the nicotine contentof cigarettes) There are no known and recommendedmdashsafe levels of cannabis use

Nevertheless the current state of play should notprevent the development and evaluation of strategiesif they are deemed to decrease the likelihood ofprobable harms without exacerbating others A majorchallenge is to discover a balance between HRapproaches (eg demand vs subsequent harm reduc-tion individual vs community policy) and the mostappropriate and acceptable messages and media bywhich to deliver them The impacts of these strate-gies may also take time to manifest and they may besubtle For example unlike the potentially moremeasurable and immediate impact of HR strategieson morbidity and mortality for other drugs such asopiates alcohol and tobacco the public health impactof HR strategies implemented for the reduction ofcannabis-related morbidity may not be immediatelyobvious or easily measurable It may be necessary toextrapolate where appropriate the impact of HRstrategies for other drugs An obvious and relativelystraightforward area for evaluation is the impact ofself-help booklets education and treatment inter-ventions for cannabis-related problems particularlycannabis dependence

It is important to be realistic and flexible in theapproach to cannabis-related harms and to continueto incorporate research findings in HR strategieswhere possible Imperfect messages about the harmsof cannabis and how to avoid or reduce them arebetter than none at all or the opposing sets ofimplausible assessments that mark contemporarydebates

Acknowledgement

Professor Wayne Hall NDARC kindly providedcomments on a draft of this manuscript


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conditions and the most appropriate responses toadolescent use (eg school expulsions)

There is also controversy about the definition andscope of harm reduction (HR) Lenton amp Sin-gle [14] in the opening contribution to this Digestseries made a distinction between HR as a broadpolicy goal and HR as a strategy They provided thefollowing practical criteria for assessing whether apolicy or programme practices HR First the centraldefining characteristic of HR is a focus on thereduction of harm as a primary goal rather than thereduction of use per se it must include strategies forthose that continue to use as well as those aimed atreduction of use or abstinence and there should besome attempt to evaluate whether these strategies willprobably result in a net reduction in drug-relatedharm [14 p213] It is important to note that HR isnot antithetical to abstinence-orientated programmesand supply reduction strategies This Digest willaccordingly cast a fairly wide net and cover issuesrelated to reductioncessation of use and reduction ofharms

Cannabis and harm reduction

This article aims to use a fairly broad approach toHR issues for a variety of reasons First the abilityto make causal inferences about the harms associatedwith chronic use in particular is hampered by a lackof longitudinal research and delays in the manifesta-tion of some adverse health and other effects anddifficulties in ruling out alternative explanations whensuch delays occur While HR for cannabis iscurrently being promoted and practiced by many inthe substance use field discussion of the issue iscontroversial Some people consider HR tacitapproval of illicit drug use or as synonymous withcalls for drug law reform More specifically forcannabis the emotive and often irrational policydebate is a major obstacle to the evaluation andrealistic reduction of cannabis-related harm partic-ularly when the type and extent of harms aredisputed The maximization and minimization ofharms by opposing camps in this debate com-promises the provision of a consistent believablemessage measurement of the costs and benefits ofHR initiatives and the evaluation of policyimpact [1517]

Having said that there is enough reason to beconcerned about the probable harms that some peoplemay encounter when using cannabis to promote

discussion and awareness of HR Cannabis would beunlike all other psychoactive drugs if it was completelybenign As described below there is research toindicate that when used in particular ways or bycertain people cannabis is associated with a variety ofadverse health and other (eg social employment)outcomes These harms may be caused more directlyby cannabis itself (eg health) or stem from currentpolicies on cannabis use (eg legal) They may have arange of impacts from an individual to the communitylevel For the sake of brevity only some of these harmsand associated HR strategies are outlined below andissues considered to be of particular interest arehighlighted It should be stressed that the followingdiscussion is not an argument for a particularlegislative or policy position

Health-related harm

Acute administration of cannabis has effects on avariety of bodily systems although these do notnecessarily disrupt functioning or predict the long-term effects of cannabis use For example while acuteadministration of small doses of cannabis producesbronchodilation chronic use may produce obstructiveairways disease [18] The risk of experiencing severetoxic effects is limited by the aversive psychotropiceffects produced by the high doses required Thistypically leads to the cessation of use before the onsetof dangerous symptoms [19] However the effects ofcannabis are variable and may also be mediated byfactors other than dose including method of use drugexperience tolerance concurrent drug use expecta-tions and personality [20]

Cannabis has a very low acute toxicity [21] and isonly a minor contributor to drug-related mortal-ity [2224] Its major public health significanceresides in its association with morbidity [15] Thepublic health significance of these outcomes is affectednot only by their severity but by the prevalence ofcannabis use As most cannabis use is experimentaland intermittent and the patterns of use producinglong-term outcomes relatively rare the greatest numberof people will experience the acute negativeeffects [15] However in terms of the relative like-lihood of experiencing the adverse health consequencesof use the major health risks are more likely to beexperienced among regular long-term users [25] Onthe basis of current use patterns it has been estimatedthat cannabis produces only small to moderate public














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Cannabis andharmreduction

Health & Medicine