Nearly all cannabis on Britain’s streets is now super-strength skunk that could be fuelling the rise in mental health problems, scientists have warned.

Researchers at King’s College London tested almost 1,000 police seizures from Kent, Derbyshire, Merseyside, Sussex and the capital in 2016 and found 94 per cent were of a dangerously high potency.

Comment: Vodka is ‘high potency’ but we don’t label it as ‘dangerously’ so. Considering cannabis is still criminalised it makes sense for it to be high potency, and smokers would, as you would do with vodka, use less.

In 2005 just 51 per cent of cannabis sold on the street was sinsemilla, also known as skunk.

Dr Marta Di Forti, Medical Research Council Clinician Scientist at King’s College warned that the powerful drug placed Britain’s 2.1 million cannabis users at risk of schizophrenia, bipolar disorder, depression, psychosis, delusions and hallucinations.

‘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,’ she said.

“It is of concern that 94 per cent of seized cannabis is now of skunk type as this potentially could increase the number of people using it and consequently the number of people experiencing harm.

“Regular users of high-potency cannabis carry the highest risk for psychotic disorders, compared to those who have never used cannabis.”

Comment: Alcohol causes multiple times more harm and it’s implicated in more cases of people suffering from psychiatric disorders.

A selection of skunk seized by British police forces in 2016


The researchers also found that in normal cannabis resin, the average concentration of tetrahydrocannabinol (THC) – the main psychoactive component – had risen by 50 per cent since 2005, from four per cent to six per cent.

In contrast, the ratio of antipsychotic cannabidiol (CBD), which helps mitigate the drug’s psychoactive effects, had fallen dramatically.

Skunk has around 14 per cent THC and is more dangerous because it contains very small amount of CBD.

In 2015 Kings College showed that in South London, 24 per cent of new cases of psychosis could be attributed to skunk use. Researchers now fear that the countrywide problem could be partly responsible for the growing number of mental health issues in Britain.

Latest figures shows there were 7,545 hospital admissions in 2016/2017 for drug-related mental health and behavioural disorders, 12 per cent higher than in 2006/2007.

There were also 14,053 admissions for poisoning by illegal drugs last year, a 40 per cent increase compared to a decade earlier.

Comment: They’re seeing similar statistics in the US but this has nothing to do with cannabis, of which there has never been a documented case of death by overdose.

Cannabis resin was also found to be stronger


Ian Hamilton, Lecturer in Mental Health, University of York, said: “If these seized samples are representative then it suggests that apart from the dominance of skunk in the UK market, it also seems that resin has increased in strength, as this analysis shows that some resin samples were nearly three times stronger than those seized back in 2005.

“So even if people are trying to source lower potency cannabis they are unable to.

“If the cannabis market is saturated with higher potency cannabis this increases the risk of younger and more naive users developing problems as they are less likely to adjust the amount of cannabis they ingest than more experienced users.”

Comment: Why are they less likely to adjust the amount? What evidence do they have for this statement? It’s actually contrary to expected human behaviour.

Prof Valerie Curran, Professor of Psychopharmacology, UCL, said: “These findings have implications for the rising numbers of young people who are becoming addicted to cannabis.

Comment: Cannabis has never been shown to be addictive, at least pharmacologically – but then Bingo can be addictive: After months of deliberation the WHO declares medical marijuana has no public health risks and should not be withheld from patients

“Evidence from our own previous research at UCL suggests that high potency varieties are more likely to lead to addiction, so if the market is dominated by these varieties then this inevitably puts more people at risk of addiction.”

The research was published in the journal Drug Testing and Analysis.