Cannabis: what does the data tell us? João Matias, Paul Griffiths, André Noor, Julián Vicente, Michael Lynskey , Wayne Hall (a)
I Cannabis in Europe
(b)
Cannabis-related indicators
Cannabis is the illicit drug most likely to be used by all age groups. The drug is generally smoked and, in Europe, is commonly mixed with tobacco. Patterns of cannabis use can range from the occasional to the regular and dependent. The increasing variety of cannabis products available on the market makes it more complex not only to analyse patterns of use but also to assess the long-term consequences of cannabis use. This is further complicated by variations in the relative concentrations of THC (the active ingredient) and CBD (an anti-psychotic) in the various products users have been exposed to over time. Moreover, the analysis of cannabis potency data may not be representative of the current markets as it is based on a subset of seizures. Overall, market dynamics, such as the shift in the demand for cannabis in Europe from resin to (domestic) herbal cannabis, suggest that over a period of time users have been exposed to different products with significant variation in content, specifically in terms of potency and contamination.
Prevalence of use Last year prevalence of cannabis use among young adults (15–34): most recent data
Adverse effects caused by cannabis consumption are often associated with specific groups of users and patterns of use. The amounts used and the frequency of use have been commonly associated with health risks, and dependency is increasingly identified as a possible consequence of regular and intensive cannabis use.
15 million young adults aged 15–34 used cannabis in the last year
Percent
Regular cannabis users are more likely to report problems
20
25 France Denmark
An estimated 1 % of European adults are daily users
15 Finland
10
Most cannabis users experiment and then stop
Bulgaria Sweden
5
The majority of cannabis users are male Percent
12.0
Resin
Trends in first-time entrants 70 000
34 %
60 000 23 %
50 000 13 %
Health Educational Selfsystem services referral
Herb Price (EUR/g)
Price (EUR/g) 3€
21 € 8€
40 000
5% Criminal system
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Price and potency
Source of referral
25 %
0
No data
Treatment
5€
25 € 8€
13 €
11 €
30 000 20 000
Other
The most frequently reported drug by new treatment entrants
Potency (% THC)
Potency (% THC)
10 000 2006
Innovations in cannabis production in recent years are cause for concern, with growers cultivating plants high in THC but low in CBD. While the potency of both forms of cannabis has risen since 2006, relatively sharp rises in the potency of resin have been seen between 2011 and 2012.
Last year prevalence of cannabis use among young adults (15–34): countries with statistically significant positive trends
2007
2008
2009
2010
2011
United Kingdom
Germany
Other countries
France
0
2012
2013
3%
2%
13 % 7%
10 % 15 %
Spain
10 %
Italy
Netherlands
Indexed trends: price and potency 100
Source: EMCDDA Statistical Bulletin 2015.
What are the adverse health effects of cannabis? Increased risk of road traffic crashes Cohort and case control studies show a 2-fold increase in risk Laboratory simulations produce impairments in driving performance Toxicology from crash victims uncertain due to potential confounding Dependence syndrome
22 %
167 113
2006
2013
Indexed trends: price and potency
188 120
100 2006
2013
Probable adverse effects of regular use Sustained daily cannabis use from adolescence to adulthood may lead to Poorer educational achievements leading to poorer occupational outcomes and welfare dependence An increased likelihood of using other illicit drugs Poorer mental health, with some evidence regarding psychoses and weaker evidence for depression and anxiety
The existence of dependence syndrome was disputed in the 1990s Recent cohort studies suggest 1 in 10 regular cannabis users can develop dependence syndrome credit: iStock
Clients seeking cannabis treatment report withdrawal syndrome
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Reference Hall, W. (2015). ‘What has research over the past two decades revealed about the adverse health effects of recreational cannabis use?’, Addiction 110(1), pp. 19-35.
Notes (a) Michael Lynskey: King’s College London (b) Wayne Hall: Centre for Youth Substance Abuse Research, University of Queensland, Australia; King’s College London
emcdda.europa.eu
