Super-strength cannabis increase prompts mental health fears

Researchers are warning of potential mental health risks after they found most of the cannabis consumed in the UK is super-strength 'skunk' or sinsemilla.

The study, conducted by King’s College London, found high-potency varieties of the drug constituted 94 per cent of police seizures in 2016, compared to 85 per cent in 2008 and 51 per cent in 2005.

Dr Marta Di Forti, clinician scientist at King’s College London’s Institute of Psychiatry, Psychology and Neuroscience, said: "In previous research we have shown that regular users of high-potency cannabis carry the highest risk for psychotic disorders, compared to those who have never used cannabis.

"The increase of high-potency cannabis on the streets poses a significant hazard to users’ mental health and reduces their ability to choose more benign types."

Researchers found the dominance of sinsemilla was due to a reduction in the availability of weaker cannabis resin; from 43 per cent in 2005 and 14 per cent in 2008, to just six per cent in 2016.

While the average concentration of THC – the main psychoactive component of cannabis – in resin increased from four to six per cent, the average concentration of THC in sinsemilla has remained at 14 per cent.

Commenting on the findings, Ian Hamilton of the University of York, said: “There are clear risks to people’s mental health as it is not just the strength of cannabis that has increased but the compounds that are thought to protect people from problems known as cannabidiols have been almost removed completely by selective breeding of cannabis.

“Higher potency cannabis seems to trigger psychosis in people who are vulnerable to mental health problems, although the risks are relatively small given the millions of people who use the drug. Roughly 1 in 20,000 users are at risk.”

A recent King’s College London study found evidence between increases in cannabis potency and first-time admissions to drug treatment, using data from the Netherlands. The research team are now investigating whether changes to the cannabis market in the UK are having a measurable impact on mental health.

Official survey findings for England and Wales show cannabis is the most commonly used drug, with around two million adults aged 16 to 59 having used it in 2016/17.

Dr Forti added: "More attention, effort and funding should be given to public education on the different types of street cannabis and their potential hazards. Public education is the most powerful tool to succeed in primary prevention, as the work done on tobacco use has proven."

The study has been published in the journal Drug Testing and Analysis. For more information go to: http://onlinelibrary.wiley.com/journal