Potency of cannabis doubled in Europe in 11 years, says study

Cannabis resin and herbal cannabis have significantly increased in potency and price, according to the first study to track changes in the drug across Europe.

The research, published in the journal Addiction, drew on data from 28 EU member states as well as Norway and Turkey, for the European Monitoring Centre for Drugs and Drug Addiction.

It found cannabis potency has doubled across Europe in the past 11 years. Concentrations of delta-9tetrahydrocannabinol or THC, the main psychoactive constituent of cannabis, in herbal cannabis rose from 5% in 2006 to 10% in 2016.

For cannabis resin, THC concentration rose from 8% in 2006 to 10% in 2011, but jumped to 17% by 2017.

The price of herbal cannabis rose from 7.36 euros per gram to 12.22 euros between 2006 and 2016, while cannabis resin rose from 8.21 euros to 12.27 euros.

Cannabis resin typically contains cannabidiol (CBD) in addition to THC. When present in cannabis, CBD may offset some of the harmful effects of THC such as paranoia and memory impairment.

However, new resin production techniques in Morocco and Europe have increased levels of THC but not CBD.

Dr Tom Freeman of the Addiction and Mental Health Group in the Psychology Department at Bath University, was lead author on the study. He said CBD has the potential to make cannabis safer, without limiting the effects users seek.

“What we are seeing in Europe is an increase in THC and either stable or decreasing levels of CBD, potentially making cannabis more harmful,” he said.

“These changes in the illicit market are largely hidden from scientific investigation and are difficult to target by policy-makers.

“An alternative option could be to attempt to control THC and CBD content through regulation,” he said.

It is estimated that 7.2% of European adults, 24 million people, used cannabis in the past year.

The study was funded by the Society for the Study of Addiction.