Abstract
Aims
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.
Design
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.
Measurements
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.
Findings
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.
Conclusions
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.