Reducing the Harms of Cannabis Use: The Policy Debate in Australia

Wayne Hall National Drug and Alcohol Research Centre

Outline

 Analysis of harms caused by cannabis use – to cannabis users and others  Analysis of harms arising from prohibition – to cannabis users and others – using Australian data  Proposals for reducing both sets of harms – under discussion in Australia  Some tentative policy prophecies

Cannabis use among Australian males, 1998 NDS Survey

80 70 60 50 40 30 20 10 0 ever used used past year past week 14-19 20-29 30-39 40-49 age group 50-59 60+

Cannabis use among Australian females, 1998 NDS Survey

80 70 60 50 40 30 20 10 0 ever used used past year past week 14-19 20-29 30-39 40-49 age group 50-59 60+

Difficulties in Assessing the Adverse Health Effects of Cannabis Use  Limited evidence base – rigour vs relevance of animal studies – paucity of epidemiological research – problems in causal inference • • other drug use user characteristics  Social context of the evaluation – polarised views – problem deflation and inflation

Acute Health Effects

 anxiety, dysphoria, panic, paranoia – especially among naive users  cognitive and psychomotor impairment while intoxicated  psychotic symptoms (probably rare) – high doses of THC – vulnerability

Accidental Injury

 Impaired performance on complex tasks  Reduced risk taking – aware of impairment  Simulated driving impaired  Epidemiological evidence unclear – measurement of impairment – confounding with alcohol

Health Effects of Chronic Use

 Respiratory disease  Dependence  Effects of Maternal cannabis use  Effects on adolescent development  Schizophrenia & psychosis  Issue of increased THC content

Respiratory Effects

 Cannabis primarily smoked  Cannabis smoke similar to tobacco smoke  Tobacco smoking causes – obstructive respiratory disease – respiratory infections – lung cancer  Most also smoke tobacco

Evidence

 Increased cough, sputum, wheeze  Histopathological changes – most marked in MT – at an earlier age  Impaired immunological responses – pulmonary alveolar macrophages  Increased health service use  Decreased respiratory function ?

Respiratory Cancers

 Cause for concern – composition of cannabis smoke – histopathological changes – case series of cancers in young adults – evidence of mutational changes in lung tissue  Case-control studies a priority

Public Health Impact of Respiratory Risks  small by comparison with tobacco – in public health terms – not in terms of personal risk  a consequence of smoking as a route – encouraging non-smoking use?

 most smoke tobacco anyway – amplification of respiratory risks

Significance of a Dependence Syndrome  Thought to have a low dependence potential – apparent absence of a withdrawal syndrome  Important for informed choice by users – users need to be aware of the risk  Increases exposure to health risks – by increasing duration of use

Evidence

 Users seeking help to stop – Australia, Sweden, & USA  Epidemiological studies – ECA 4% population lifetime – NCS 4% population lifetime – NSMWHB 2% of population past year

Tolerance and withdrawal

 tolerance in animal & human studies  withdrawal syndrome in animals – elicited by cannabinoid antagonist  withdrawal symptoms in human laboratory studies: – irritability, anxiety, insomnia, depression  these common in clinical populations

Clinical features

 a withdrawal syndrome common in users seeking help  compulsive use patterns – also common in problem users  perceived to be a problem?

– by a minority who meet criteria in community – as for alcohol & other drugs

Risks and Consequences

 Risks – 9% of lifetime users (NCS study) – 33-50% of daily users  Consequences?

– respiratory symptoms – impaired memory – poor work performance – social disapproval

Need for Treatment

 Fewer than 10% seek any treatment  Why so few?

– high rates of remission?

– fewer consequences?

– existing treatment services unattractive?

 How treatable?

– self-help – brief interventions – psychotherapy

Adolescent Development

 Concerns – educational performance – progression to “harder” drugs  Issues – rarity of heavy use – causal attribution • • other drug use user characteristics

Natural history of cannabis use

under prohibition  initiation in mid teens  most use intermittent – relatively low capture rate for daily use  discontinue mid to late 20s – impact of marriage, mortgages & children  persistent use relatively rare – predicted by early initiation – heavier use

Current monthly use of various drugs by age (Chen & Kandel, 1995) 100 90 80 70 60 50 40 30 20 10 0 10 12 14 16 18 20 22 age 24 26 28 30 32 34 alcohol cigarettes cannabis other illicit prescribed psychoactives

Educational Performance

 Cross sectional studies  Longitudinal studies US & NZ – selective recruitment to use – peer influence – small direct contribution  Educational implications – exculpation & blame – school policies

A Gateway Drug?

 Cross-sectional & longitudinal studies  Sequence of drug involvement – alcohol & tobacco precede – cannabis which precedes – heroin & other drugs  < 5% of cannabis users use “harder” drugs  Progression predicted by: – earlier initiation & heavier use

Explanations

 selective recruitment to use – at risk & troubled youth more likely to use  peer networks – regular users affiliate with peers who use – peer culture supportive of drug use & crime  drug markets – provide opportunities to use other illicit drugs  genetic vulnerability to drug dependence

Cannabis & Psychosis

 “Cannabis psychosis” – toxic psychosis – functional psychosis  Cannabis as a risk factor for schizophrenia – precipitation – exacerbation

Potential significance

 High prevalence of cannabis use – especially at period of risk for psychosis – complicates causal attribution  Additional cases of psychosis  Exacerbation of psychosis  Suffering of affected persons & families  Costs of treating psychoses

“Cannabis Psychoses”

 Conflicting opinions – clinical observations – limited case-control evidence  Probably exist but rare – either require large doses of THC – or vulnerability  Ethically difficult to reduce uncertainty

Cannabis & Schizophrenia

 Cannabis & schizophrenia associated – in general & clinical populations  Cannabis use probably exacerbates disorder – reasonable prospective evidence  Possibly precipitates disorder in vulnerable – Swedish conscript study  Less likely to cause disorder

de novo

– no evidence of rising prevalence

The Issue of Potency

 Claim THC content of cannabis x 30 times  Absence of good data: – testing not required – or done regularly  Media publicity to unusual cases – biased sampling  Changes in patterns of use – earlier initiation – heavier use of more potent forms

THC content of Marijuana 1980-98 : US

Potency Monitoring Project

5 4 3 2 1 0 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98

Changing Patterns of Cannabis Use

 Most users smoke “heads”and use bongs  Weekly+ use accounts 96% of market  Earlier initiation of use: – more regular use by younger users – more problem users?

 More use among vulnerable groups • • persons with schizophrenia conduct disordered adolescents  More obvious problem users

Possible Effects of Increased Potency  For naive users: – higher risk of dysphoric & psychotic symptoms • higher rates of discontinuation?

– higher rates of accidental injury?

 For regular users: – lower respiratory risk, if users titrate dose – higher risk of dependence? • especially among adolescents – more cognitive impairment?

Summary: adverse health effects

 Dependence – 10% chance for users – 33-50% for daily users – consequences?

 Respiratory disease – chronic bronchitis – cancer?

 Motor vehicle accident risk?

Risks of Chronic Use

 Adolescent use – selective recruitment to use – peer influences – indicator of at risk status  Psychosis – probably produces symptoms – probably exacerbates and possibly precipitates schizophrenia in vulnerable

Overall Assessment

 On

current patterns of use

– small to moderate public health impact – less than alcohol & tobacco – with possible exception of MVA, harms caused to users  Do these adverse effects justify prohibition?  Would relaxing prohibition increase: – rates and duration of regular cannabis use?

– rates of problems related to cannabis use?

Putative Harms Caused by Cannabis Prohibition

 Loss of individual liberty to use cannabis  A large scale cannabis blackmarket – controlled by criminals – unregulated and no quality control – untaxed by government – corruption of public officials  Arms race in policing technology – helicopters and satellite surveillance – indoor hydroponic cultivation

The Harms of Prohibition:

Effects on Rule of Law  Discriminatory non-enforcement of law – only 1-2% of past year users are prosecuted – more often lower SES, unemployed males  Brings law into disrepute among the young  Effects on users of conviction – stigma of criminal record – no impact on cannabis use – disproportionate penalty for self-harm

The Harms of Prohibition:

Inefficient Uses of Scarce Resources  Paradox of cannabis law enforcement • • most cannabis use goes undetected but majority of drug offences are for cannabis use  Inefficient use of scarce resources: • police and Criminal Justice System  Loss of medical uses of cannabis products • • e.g. anti-nausea agent & appetite stimulant analgesic and antispasmodic

Options for Reducing

Cannabis-related harms  Intensified enforcement of prohibition – US and Swedish models  Legalisation of cannabis use – de facto e.g. the Netherlands – or de jure  “Decriminalisation”: – prohibition with civil penalties – diversion into treatment or education

Intensification of Prohibition

 American model – substantial fines and gaol sentences – workplace drug testing – school education & mass media campaigns – “zero tolerance” and strong social disapproval  Swedish model – disapproval similar to US – compulsory treatment rather than imprisonment

Problems with Intensified Enforcement  Costs of implementation • • imprisonment or compulsory treatment expanding role of government vs general retreat  Presupposes societal consensus • absent in Australia where opinion divided  Limits to effectiveness • • may have decreased use in USA but rising again may be easier to keep low as in Sweden  Backlash against prohibition?

• excessive zeal in enforcement favours reformists

Cannabis Legalisation

 a minority option in Australia (25%) – credibility of opponents and proponents  an irreversible step  likely to increase heavy & regular use – experience with alcohol & other drugs  contrary to international treaties – and international sentiment

Decriminalisation Pros Cons

 A cautious step – easily reversed  Reduces – – harms to users discriminatory enforcement  Better use of scarce resources  Minimal impact on use  Little or no effect on blackmarket  Inconsistent: – – use not a crime but sale is  Symbolism – implies cannabis use is safe & acceptable

A Choice of Evils

 Insufficient data for utilitarian analysis  Trading off incommensurable values: – users’ health – social disorder and crime – civil liberties  A task for the political system – polarisation of public opinion – lack of consensus on trade-off – minimal changes to status quo most likely

Reduced Penalties for Personal Use  Removal gaol penalties for 1st offenders –

de jure

recognition of practice  Cautioning and diversion as an alternative – may increase number of users dealt with – a proportionate response to self-harm

Reduced Penalties for Personal Use  Reduce push for more radical reform – more reversible policy – consistent with international agreements  Coupled with penalties for use when driving – to address most probable adverse effect on non-users  Graduated penalties based on THC content?

A Necessary Breathing Space?  Epidemiological research on adverse effects – – on adolescent development serious long term health consequences • cancers, respiratory disease, psychosis  More credible health education – – scepticism about scares among young parallels with the effects of alcohol & tobacco: • respiratory risks, MVA, dependence, psychosis  Better assessment of therapeutic uses – – AIDS& cancer related nausea and wasting neurological diseases and intractable pain