"Cannabis: An apology

Record numbers of teenagers are requiring drug treatment as a result of smoking skunk, the highly potent cannabis strain that is 25 times stronger than resin sold a decade ago.

More than 22,000 people were treated last year for cannabis addiction - and almost half of those affected were under 18. With doctors and drugs experts warning that skunk can be as damaging as cocaine and heroin, leading to mental health problems and psychosis for thousands of teenagers, The Independent on Sunday has today reversed its landmark campaign for cannabis use to be decriminalised.

A decade after this newspaper's stance culminated in a 16,000-strong pro-cannabis march to London's Hyde Park - and was credited with forcing the Government to downgrade the legal status of cannabis to class C - an IoS editorial states that there is growing proof that skunk causes mental illness and psychosis.

The decision comes as statistics from the NHS National Treatment Agency show that the number of young people in treatment almost doubled from about 5,000 in 2005 to 9,600 in 2006, and that 13,000 adults also needed treatment.

The skunk smoked by the majority of young Britons bears no relation to traditional cannabis resin - with a 25-fold increase in the amount of the main psychoactive ingredient, tetrahydrocannabidinol (THC), typically found in the early 1990s. New research being published in this week's Lancet will show how cannabis is more dangerous than LSD and ecstasy. Experts analysed 20 substances for addictiveness, social harm and physical damage. The results will increase the pressure on the Government to have a full debate on drugs, and a new independent UK drug policy commission being launched next month will call for a rethink on the issue.

The findings last night reignited the debate about cannabis use, with a growing number of specialists saying that the drug bears no relation to the substance most law-makers would recognise. Professor Colin Blakemore, chief of the Medical Research Council, who backed our original campaign for cannabis to be decriminalised, has also changed his mind.

He said: "The link between cannabis and psychosis is quite clear now; it wasn't 10 years ago."

Many medical specialists agree that the debate has changed. Robin Murray, professor of psychiatry at London's Institute of Psychiatry, estimates that at least 25,000 of the 250,000 schizophrenics in the UK could have avoided the illness if they had not used cannabis. "The number of people taking cannabis may not be rising, but what people are taking is much more powerful, so there is a question of whether a few years on we may see more people getting ill as a consequence of that."

"Society has seriously underestimated how dangerous cannabis really is," said Professor Neil McKeganey, from Glasgow University's Centre for Drug Misuse Research. "We could well see over the next 10 years increasing numbers of young people in serious difficulties."

Politicians have also hardened their stance. David Cameron, the Conservative leader, has changed his mind over the classification of cannabis, after backing successful calls to downgrade the drug from B to C in 2002. He abandoned that position last year, before the IoS revealed that he had smoked cannabis as a teenager, and now wants the drug's original classification to be restored."