Tom P. Freeman, Teodora Groshkova, Andrew Cunningham, Roumen Sedefov, Paul Griffiths ,Michael T. Lynksey
Declarations of interest: No authors report any declarations of interest. This study was funded by a Senior Academic Fellowship from the Society for the Study of Addiction awarded to TF. The funder had no role in the study design, data analysis, interpretation, writing of the report or the decision to submit for publication.
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/add.14525.
To quantify changes in (i) potency (concentration of Δ9‐tetrahydrocannabinol; %THC), (ii) price (Euros/gram of cannabis), and (iii) value (quantity of THC per price unit; mg THC/Euro) of cannabis resin and herbal cannabis in Europe.
Repeated cross‐sectional study.
Setting and participants
Data collected from 28 EU member states, Norway and Turkey by the European Monitoring Centre for Drugs and Drug Addiction.
Outcome variables were potency, price, and value for cannabis resin and herbal cannabis in Europe, 2006‐2016. Inflation was estimated using the Harmonised Indices of Consumer Prices. Mixed effects linear regression models were used to estimate linear and quadratic time trends, with a random intercept and slope fitted to account for variation across countries.
Resin potency increased from a mean (95% CI) of 8.14% THC (6.89, 9.49) in 2006 to 17.22 (15.23, 19.25) in 2016. Resin price increased from 8.21 Euros/gram (7.54, 8.97) to 12.27 (10.62, 14.16). Resin increased in value, from 11.00 mg THC per Euro (8.60, 13.62) to 16.39 (13.68, 19.05). Quadratic time trends for resin potency and value indicated minimal change from 2006‐2011, followed by marked increases from 2011‐2016. Herbal cannabis potency increased from 5.00% THC (3.91, 6.23) to 10.22 (9.01, 11.47). Herbal price increased from 7.36 Euros/gram (6.22, 8.53) to 12.22 (10.59, 14.03). The value of herbal cannabis did not change from 12.65 mg of THC (10.18, 15.34) to 12.72 (10.73, 14.73). All price trends persisted after adjusting for inflation.
European cannabis resin and herbal cannabis increased in potency and price from 2006‐2016. Cannabis resin (but not herbal cannabis) increased in the quantity of Δ9‐tetrahydrocannabinol per Euro spent. Marked increases in resin potency and value from 2011‐2016 are consistent with the emergence of new resin production techniques in European and neighbouring drug markets.
add14525-sup-0001-Data_S1.pdfPDF document, 248.1 KB
Table S1: Country‐specific information on coverage and sampling of cannabis potency data
Table S2: Country‐specific information on coverage and sampling of cannabis price data
Figure S1. Changes in resin potency in Europe by year, 2006‐2016.
Figure S2. Changes in herbal potency in Europe by year, 2006‐2016.
Figure S3. Changes in resin price in Europe by year, 2006‐2016.
Figure S4. Changes in herbal price in Europe by year, 2006‐2016.
Figure S5. Changes in value of cannabis resin in Europe by year, 2006‐2016.
Figure S6. Changes in value of herbal cannabis price in Europe by year, 2006‐2016.