Seldom does a leading newspaper take a high-profile stand in favour of drug liberalisation. It is less common still for such a campaign to be publicly retracted. The Independent on Sunday deserves great credit for having the courage to change its mind on cannabis on the basis of mounting evidence of just how dangerous the world's most popular illicit drug has become.
It cannot have been an easy decision. Many readers undoubtedly subscribe to the vague, laissez-faire tolerance of cannabis increasingly prevalent among educated people in Western countries. That growing consensus needs to be challenged.
Supporters of legalisation would have us believe that cannabis is a gentle, harmless substance that gives users little more than a sense of mellow euphoria and hurts no one else. It's not an unattractive image. Sellers of "skunk" know better. Trawl through websites offering cannabis seeds for sale and you will find brand names such as Armageddon, AK-47 and White Widow. "This will put you in pieces, then reduce you to rubble - maybe quicksand if you go too far," one Glasgow-based seller boasts. This is much closer to the truth.
The cannabis now in circulation is many times more powerful than the weed that today's ageing baby-boomers smoked in college. In the flower-power era, the concentration of THC, as the main psychoactive substance in cannabis is known, was typically 2 or 3 per cent. Present-day cannabis can contain 10 times as much.
Today's skunk is a product of several developments in cannabis cultivation: the "sinsemilla technique" (the cultivation of only unfertilised female plants); the use of indoor growing technologies; and the use of plant strains bred for higher yield and potency.
Evidence of the damage to mental health caused by cannabis use - from loss of concentration to paranoia, aggressiveness and outright psychosis - is mounting and cannot be ignored. Emergency-room admissions involving cannabis are rising, as is demand for rehabilitation treatment.
Amid all the libertarian talk about the right of individuals to engage in dangerous practices provided no one else gets hurt, certain key facts are easily forgotten. First, cannabis is a dangerous drug - not just to the individuals who use it. People who drive under the influence of cannabis put others at risk. Would even the most ardent supporter of legalisation want to fly in an aircraft whose pilot used cannabis?
Second, drug control works. More than a century of universally accepted restrictions on heroin and cocaine have prevented a pandemic. Global levels of drug addiction - think of the opium dens of the 19th century - have dropped dramatically in the past 100 years. In the past 10 years or so, they have remained stable. The drug problem is being contained and our societies are safer and healthier as a result.
The exception is cannabis, the weakest link in the chain. It is a weed that grows under the most varied conditions in many countries, which makes supply control difficult. But we can tackle demand, especially among the young. That need not mean sending them to jail. Young people caught in possession of cannabis could be treated in much the same way as those arrested for drink driving -- fined, required to attend classes on the dangers of drug use and threatened with loss of their driving licence for repeat offences.
I am increasingly convinced countries get the drug problem they deserve. Those that invest political capital - backed by adequate resources - in prevention, treatment and rehabilitation are rewarded with significantly lower rates of drug abuse.
Sweden is an excellent example. Drug use is just a third of the European average while spending on drug control is three times the EU average. For three decades, Sweden has had consistent and coherent drug-control policies, regardless of which party is in power. There is a strong emphasis on prevention, drug laws have been progressively tightened, and extensive treatment and rehabilitation opportunities are available to users. The police take drug crime seriously.
Governments and societies must keep their nerve and avoid being swayed by misguided notions of tolerance. They must not lose sight of the fact that illicit drugs are dangerous - that is why the world agreed to restrict them.
The global cannabis market is changing. Traditional suppliers to the UK such as Morocco - the world's largest producer of cannabis resin - are slashing cultivation. That is more than offset by an increase in home-grown cannabis, now the main source of supply for most major markets. In Britain, demand will increasingly be met by well-organised indoor production with links to criminal networks. This represents a growing challenge for police.
Drug prevention and treatment will need to change in response to the effects of more powerful cannabis varieties on cognitive capacity, memory and emotional development, as well as schizophrenia among vulnerable individuals exposed to the drug. Public attitudes also need to change. The IoS has provided a valuable lead. It is time to explode the myth of cannabis as a "soft" drug.
The writer is executive director of the United Nations Office on Drugs and Crime
"I have been a productive, happy citizen my entire adult life and have regularly consumed cannabis since I was 13 (I am now 40). How is it that I have not suffered from the pernicious effects you cite? Simply, I have used cannabis responsibly." David Scheiner, LONDON
"Is cannabis addiction leading to the development of schizophrenia? Or is schizophrenia a mental impairment which can cause an obsessive consumption of any kind of hallucinogenic drug?" Juan Luis Domínguez, GIRONA, SPAIN
"The increased numbers of people seeking medical advice for cannabis-related problems in the UK reflects an increase in people's willingness to seek such advice. This is a positive result of the issue being brought into the legal and social mainstream." G J Kennedy, GLASGOW
"What has happened in countries which have legalised cannabis? The UK, with its "just say no" attitude, has a much higher consumption rate, especially among young people, than any country where it is legal." Peter Simmons, LEOMINSTER, HEREFORDSHIRE
"A lot of people would much prefer a far weaker strain of cannabis. The problem in obtaining this lies with prohibition. With prohibition in place, the trade is put into the hands of organised criminals, all of whom will want to increase their market share and profit. To do this, they are repeatedly making their skunk stronger in order to get the user more high than any competitors' skunk. This is resulting in the massive, and very sudden, escalation in the amount of people reacting badly to the drug that you documented in you paper on Sunday. It is, unfortunately, a trend that will continue until legalisation of the drug." Tomas Mogford, BY EMAIL
"You say that cannabis used to be a benign substance, which a policy of prohibition has spent 30-odd years trying to eradicate. This programme of eradication has, according to you, resulted in a new and massively more damaging version of the drug coming into existence. How, then, do you conclude that prohibition is the right policy when clearly it has created the very problem you now seek to highlight?" Derek Williams, BY EMAIL
"What joy to read your headline "Cannabis: an apology". I belong to an organisation for the families of drug abusers and have seen at first hand what damage cannabis can do to young brains. I watched it destroy my son's youth, and ruin his life. For him it is too late, but maybe now sense will prevail and future generations will be better protected." Judy Yates, DORKING, SURREY
"Nobel laureate Professor Milton Friedman said in 1991, "Under prohibition of alcohol, deaths from alcohol poisoning, from poisoning by things that were mixed in with the bootleg alcohol, went up sharply. Similarly, under drug prohibition, deaths from overdose, from adulterations, from adulterated substances have gone up." He remains resolutely against prohibition and not on libertarian but economic and moral grounds. You would do well to listen to this voice of reason." Richard Wilson, BICESTER, OXFORDSHIRE
"I can't thank you enough for Sunday's articles on skunk. My 18-year-old son is currently awaiting trial for his last violent outburst fuelled by his six-year addiction to the drug. I have watched helplessly as he has spiralled into self-destruction. He has transformed from a sharp-witted loving child into a monster. It is the hardest thing in the world to ask the police to take your own child away and thrust him into the criminal justice system when you know what he really needs is drugs counselling. I am delighted that, at last, hordes of terrified parents have been given a voice." Francesca Tolcher, BY EMAIL
"We first warned in 2003 of the increase in young people running into problems with cannabis. The illicit drugs industry is one of the largest industries in the world and it is entirely unregulated. Consequently, cannabis can be sold freely to children, which would seem preposterous for alcohol or tobacco. Sadly, the only way forwards that I can see is to bring cannabis further into the sphere of the law, which would set appropriate age limits on use." Professor Richard Hammersley, DIRECTOR, CENTRE FOR BEHAVIOURAL ASPECTS OF HEALTH AND DISEASE, GLASGOW CALEDONIAN UNIVERSITY
"There is no evidence that cannabis causes or worsens mental illness. Is the Misuse of Drugs Act meant to limit choices or reduce harm? It has not reduced use and there seems more harm now than ever - not just a risk of worsening illness, but a risk of smoking contaminants and adulterants." Alun Buffry, LEGALISE CANNABIS ALLIANCE
"My brother is schizophrenic, and I have no doubt that cannabis was a contributing factor. Yet its criminality makes support of the victim harder at every stage. Turning a disturbed teenager into a criminal will remain with those who introduced it to him for the rest of their lives." Name and address withheldReuse content