Talk of the prevalence of cannabis provokes calls for decriminalisation if not legalisation. Don't do it, argues Antonio Maria Costa
Supporters of the legalisation of cannabis would have us believe that it is a gentle, harmless substance that induces little more than a sense of mellow euphoria.
Sellers of the world's most popular illicit drug 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 seller boasts.
This is much closer to the truth. The reality is that the cannabis now in circulation is many times more powerful than the weed which many of today's ageing baby-boomers smoked. The characteristics of cannabis are no longer that different from those of other plant-based drugs such as cocaine and heroin.
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. These health problems are increasingly being observed in young people.
The 2006 World Drug Report, published recently by the UN Office on Drugs and Crime, shows that some 4 per cent of the world's adult population - that's around 162 million people - use cannabis at least once a year, more than all other illicit drugs combined (the latest figure for Ireland is 5.1 per cent, close to the EU average).
Little is known about the true extent of cannabis cultivation around the world. What is clear is that the drug is under-estimated and becoming more potent.
The global market is estimated at around €109 billion, so this is big business. A market that size inevitably attracts organised crime. The proceeds of the drugs trade fuel other forms of crime. Cannabis is therefore a security threat as well as a health risk.
Amid all the libertarian talk about the right of the individual to engage in dangerous practices provided no one else gets hurt, certain key facts are easily forgotten.
Firstly, 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?
Secondly, drug control works. More than a century of universally accepted restrictions on heroin and cocaine have prevented what would otherwise have been a pandemic.
Global levels of drug addiction have dropped dramatically in the past 100 years. In the past 10 years or so, they have remained stable.
Cannabis is the weakest link in the international effort to contain the world drugs problem. In theory, it is a controlled substance. In practice, it is running rampant.
It is both a weed that grows under the most varied conditions in many countries, as well as a high-yielding plant that can be grown indoors. This makes supply control difficult.
But we can tackle demand, particularly 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 drunk-driving - fined, required to attend classes on the dangers of drug use and threatened with loss of their driving licence for repeat offences. Prison would be a last resort. Schools and universities should apply zero tolerance.
National policies on cannabis vary and sometimes change from one year to the next. The experience of countries which were more tolerant of cannabis use is ambiguous and not persuasive.
The distinction between "soft" and "hard" drugs is, at best, artificial, especially with such a damaging psycho-active substance as modern-day cannabis. Even some advocates of cannabis as a "soft" drug are now re-considering as they observe the devastating health consequences of abuse.
With cannabis-related health damage increasing, it is fundamentally wrong for countries to make cannabis control dependent on which party is in power.
Policy reversals leave people confused as to just how dangerous cannabis is. Like other public health challenges, the cannabis pandemic requires political consensus, both within countries and internationally.
The world's experience with tobacco is instructive. Consumption of cigarettes grew steadily throughout the 20th century to reach what the World Health Organisation calls a global epidemic. Prevalence rates are about 35 per cent in rich countries and 50 per cent in the developing world.
Nevertheless, the successes seen in reducing tobacco consumption in the past 10 years show that preventive measures can help to change attitudes.
It took nearly half a century for clear medical evidence of the links between smoking and lung cancer to translate into systematic anti-smoking policies by governments. In more and more countries, with Ireland taking the lead in Europe, bans on smoking in public places are now widely accepted.
Let us draw the right conclusions. Cannabis is dangerous. We ignore it at our peril.
Antonio Maria Costa is executive director of the United Nations Office on Drugs and Crime