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Young people and cannabinoids: current research and implications for tobacco control

London SFN

Harry Sumnall

on 14 October 2013

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Transcript of Young people and cannabinoids: current research and implications for tobacco control

Professor Harry Sumnall
Centre for Public Health, LJMU

Young people and cannabinoids: current research and implications for tobacco control
"The best evidence based advice to help cannabis smokers look after their lungs would be to abandon the peculiar British habit of mixing cannabis with tobacco” (Prof D. Nutt, June 2012)
Alternatives to smoking?
Small case studies & cross sectional surveys
Tobacco use decreased - refused to return to smoking;
Self-reported respiratory symptoms significantly improved.
Measures of lung function (forced expiratory volume (FEV1) and forced vital capacity (FVC)) improved.
Need for a larger clinical trial
Vapourisers can create THC blood levels that are comparable to smoking, but unlike smoke, the vapour contains little other than cannabinoids
Good quality vapourisers are expensive (£100+)
Not very practical for many users
UK cannabis culture of smoking joints
Under Section 9A of the Misuse of Drugs Act 1971, it is a criminal offence to supply or offer to supply articles for administering or preparing controlled drugs.
About me
Professor of Substance Use, CPH, LJMU
President, EUSPR
Member, ACMD
Conduct funded research into prevention, evidence based practice/policy, psychopharmacology
What links tobacco and cannabis use?
Strong epidemiological evidence to show co-use of cannabis and tobacco
Most common form of polydrug use (involving an illegal substance)
In the UK cannabis historically smoked with tobacco - availability, price, smoking behaviour (vs USA)
Joints produce greater increases in plasma THC and subjective ratings of intoxication, strength, and quality compared to pure cannabis joints ('blunts').
Cannabis use is associated with initiation of tobacco in teens
Smoked tobacco use is a predictor of cannabis use, especially in young adulthood
e.g. in one Australian study, weekly teen use of cannabis predicted a more than eightfold increase in the odds of later initiation of tobacco use
For 21-year-old smokers, not yet nicotine-dependent, daily cannabis use raised the odds of nicotine dependence at the age of 24 years more than threefold
Looking at other factors, cannabis use seems second only to previous tobacco use as a predictor of tobacco dependence.
Reverse 'gateway'?
Shared route of administration - 'learning to smoke'
Tobacco in joints?
Effect still significant after controlling for peer use of tobacco
Not a motivational effect, previous cannabis use not always associated with reduced tobacco quit attempts/success
Common actions on brain reward systems?
Substitution effect, e.g. at school, work
Alleviation of cannabis withdrawal?
UK cannabis joint smokers are therefore tobacco users. In effect, are many of the risks of cannabis use the same as that of tobacco?
Do cannabis joint smokers self-identify as being tobacco smokers? Implications for prevention
Very few studies have specifically investigated prevention of co-use of tobacco and cannabis
More studies have investigated prevention of cannabis (which would also include co-use)
Most studies are in school aged children, fewer in older young people, and adults
Majority from the USA
Prevention approaches
US Iowa Strengthening Families Program, slowed the growth of polysubstance use (including tobacco and cannabis) from 6th through 12th grades
Enforcement of smoke free US University halls of residence policies led to reduced cannabis use
Brief 1 to 1 consultation about health promotion led to reduced use frequency at + 12 months
UK BI in FE colleges showed short (+3m) but not long (+12m) term effects on tobacco and cannabis use
(Swiss)YP views vs tobacco
"Cannabis is more natural"
"Cannabis is more healthy"
"Cannabis is more ethical"
"Tobacco has no purpose"
"Easier to quit joints than tobacco"
Cannabinoid receptor agonists ('synthetic cannabis')

Potentially hundreds available, only a small number controlled under the Misuse of Drugs Act 1971
Cannabis-like effect: mild euphoria, relaxation, introspection, perceptual changes
Many have a greater potency at CB1/CB2 R than ‘natural’ THC (full vs partial agonist activity)
Effects of herbal cannabis on memory problems, psychopathology and psychosis proneness dependent on THC:CBD ratio
CBD is an indirect antagonist of THC, thus moderating some of the adverse psychological effects of cannabis.
Smoking mixtures lack the moderating effect of CBD
Long term effects unknown
School based prevention
School based cannabis prevention activities *can* have an impact upon use:
Meta analysis of 15 studies (n=15,571 students) produced a moderate effect size of 0.58
Social learning/influence approaches had less of an effect than other types
Length of programme important (e.g. >15 sessions)
Delivery by non-teachers more effective
Delivery to older students has greater effect

(Porath Waller et al., 2010)
UK Youth attitudes (from Eurobarometer 2011):
59% want cannabis to remain banned; 34% regulated; 5% available without restriction
15% want tobacco to be banned; 65% regulated, 19% available without restriction
57% favour 'tough measures against dealers'
36% favour reduction of poverty and unemployment as the best way to reduce drug problems
Mental health risks
Longitudinal studies from Sweden, Israel, ND, NZ suggest that risk of developing psychotic symptomatology or being hospitalised with schizophrenic disorder is approximately doubled in cannabis users
Brief psychotic episodes, exacerbation and return of symptoms, poor medication response etc. also important
Risk still low
Modelling by Hickman and colleagues ('09/'10) suggests that you would need to prevent between 3000-5000 heavy, and 10-30,000 light users from smoking to prevent a single case of schizophrenia
Considering small effects of intervention, uncertain cost-effectiveness, lack of availability and investment, prevention of mental health problems in general pop. shouldn't be focus of interventions
Cannabis prevention should be considered an important component of tobacco prevention efforts
For many UK users, health harms of cannabis are the same as tobacco
Preventing lifetime use probably less important than progression into heavy patterns of use
Can we persuade users to remove tobacco from their polydrug repertoires?
How can we work within existing laws and regulations?
Prevention can work!
Information provision alone does not change cannabis use behaviour
Because cannabis is illegal we have fewer 'tools' available to us to reduce use/harms
Fewer controls over 'marketing'
*Mostly * privately smoked, hence few environmental interventions
Few opportunities for supportive community based interventions
Few opportunities for 'self-help'
No useful 'THC replacement therapy', although Sativex being trialled in Australia
June 2012 BLF report :
"Risk of developing lung cancer is up to twenty times greater in a cannabis cigarette than in a tobacco cigarette – yet 88% of the public believe tobacco cigarettes pose the greater risk"
"A third of people believe cannabis does not harm your health - despite established scientific links to TB, acute bronchitis, lung cancer and other health problems"
No critical appraisal of cited studies - small, 'underpowered' studies
Conflicting evidence on lung cancer, some studies show no effect, or even protective effect.
Use patterns important - effects only seen in long term smokers (10+ years); linear effects incorrectly assumed
Co-use of tobacco v.important
36% classed as 'frequent users'
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