UN warns of cannabis dangers as it backs 'IoS' drugs 'apology'

The United Nations has issued an unprecedented warning to Britain about the growing threat to public health from potent new forms of cannabis, saying there is mounting evidence of "just how dangerous" the drug has become.

Writing in today's Independent on Sunday, Antonio Costa, the executive director of the UN Office on Drugs and Crime, says each country has the "drug problem it deserves", and warns that the British government must "avoid being swayed by misguided notions of tolerance".

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Mr Costa's comments follow disclosures in last week's IoS that a record 22,000 people needed National Health Service treatment last year for drug rehabilitation, together with doctors' warnings that skunk cannabis is creating a generation with mental health problems.

He says: "Many [people] subscribe to the vague, laissez-faire tolerance of cannabis which is increasingly prevalent among educated people in Western countries. That consensus needs to be challenged. Evidence of the damage to mental health caused by cannabis use is mounting and cannot be ignored."

The intervention, which will be seen as an attack on the Government's liberal stance on cannabis use, follows the decision by the IoS to reverse its support for the drug to be decriminalised, 10 years after launching a high-profile campaign for legalisation.

Mr Costa proposes that young people found in possession of the drug should be penalised in the same way as people caught drink driving, adding that the cannabis "now in circulation is many times more powerful than the weed that today's baby-boomers smoked in college. Cannabis is a dangerous drug."

After a week of debate in newspapers, television and radio ­ as well as outrage on pro-cannabis websites and blogs ­ the UN's unprecedented foray into the debate about drugs policy coincided with a new study proving links between mental health problems and smoking skunk. Research published yesterday predicts that cannabis may account for a quarter of all new cases of schizophrenia in three years' time.

The study, published in the journal Addiction, also says that rates of schizophrenia will increase substantially by the end of the decade, particularly among young men. The use of cannabis among under-18s rose 18-fold in the 30 years to 2002, according to the researchers from Bristol University.

Dr John MacLeod, co-author of the study, said: "If you assume such a link [with cannabis] then the number of cases of schizophrenia will increase significantly in line with increased use of the drug."

Sir Richard Branson, a prominent supporter of the IoS campaign for decriminalisation, yesterday added his voice to those calling for the new facts about skunk to prompt a policy rethink.

"The arrival of genetically engineered skunk has merited a new look at the situation," Sir Richard said. "If people have serious problems with drink, drugs or cigarettes, there should be NHS centres to help them where they can walk in free from blame."

Additional reporting: Rob Sharp and Chris Havergal