Stronger cannabis posing greater threat to health, say experts

The potency of cannabis has increased over the past 50 years, leading to more severe health problems for users, a recent investigation has shown.

Research conducted at the University of Bath has revealed that cannabis resin and herbal cannabis are becoming progressively worse in their effects.

Concentrations of the dangerous and addictive compound delta‐9‐tetrahydrocannabinol (THC) were found to have increased in cannabis resin by 24 per cent and in herbal cannabis by 14 per cent over the past 50 years.


Dr Tom Freeman, the main author of the report, said: “As the strength of cannabis has increased, so too has the number of people entering treatment for cannabis use problems.”

He added: “More Europeans are now entering drug treatment because of cannabis than heroin or cocaine.”

The study by the Addiction and Mental Health Group stated that exposure to increasing doses of THC over time could increase the “risk of developing psychosis and risk of relapse in people with psychosis”.

More Europeans are now entering drug treatment because of cannabis than heroin or cocaine.


But calls by Dr Freeman for the introduction of “a standard unit system for cannabis” like that for alcohol to help people use the drug “more safely” has been greeted with dismay.

Speaking to the Daily Mail, Mary Brett of the anti-drug charity Cannabis Skunk Sense said: “This is a very dangerous drug and there is no safe limit of consumption.

“Someone smoking a cannabis joint for the very first time can become psychotic.

“Cannabis is highly unpredictable and can have a wide range of negative effects on the body, not just the brain but other aspects of health, too, including the lungs and the immune system.”


A press release, issued by the University of Bath to coincide with the publication of the study, reported that cannabis is “the most widely used illicit drug in the world”.

Currently, cannabis – a Class B drug in the UK – has only been legalised in a few US states and four other countries worldwide.

New Zealand recently rejected a move to legalise recreational cannabis in a public referendum.

Also see:

NZ referendum rejects cannabis legalisation

Cannabis use costs Australia billions

Cannabis use linked to multiple murders by teens