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

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Cannabis use among Australian females, 1998 NDS Survey

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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 useunder 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)

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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

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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