Median THC concentrations in herbal cannabis were reported by 22 countries. Between 2010 and 2019, THC concentration modestly increased, from 6·9% (Interquartile range (IQR): 4·7 to 9·2%) to 10·6% (IQR: 7·2 to 12·7%; see also Figure 5). Regression analyses suggest that THC concentrations in herbal cannabis did not significantly decline in any country in Europe. However, significantly increasing THC concentrations in herbal cannabis rose were identified in six countries (Portugal, Estonia, Czechia, Poland, Sweden, Hungary) at an annual rate of 0·5 to 1·1 percentage points.
