Details of the clampdown are published today in New Scientist magazine, and have been confirmed separately by The Independent. A member of the international panel said yesterday that he wanted the findings published: "I felt comfortable having it in our draft, and I thought it was useful information."
Had the WHO published their work, it would have given cannabis a public and scientific legitimacy that the United States and United Nations have long denied, as part of their "war against drugs". But there is growing evidence that the criminalisation is unjustified.
In a special investigation into the drug, New Scientist concludes that "politicians will just have to bite on the bullet - cannabis will have to be decriminalised". It is the most prominent scientific publication so far to provide backing for the Independent on Sunday's campaign to decriminalise cannabis use in the UK.
In an editorial, the magazine says that "despite the anti-dope propaganda that circulates in the US, most people are thankfully well aware that no great social disaster has befallen The Netherlands, where cannabis has been sold openly in coffee shops for years".
It adds that "only the politicians still seem irrationally terrified by the idea of any relaxation in the law: they think they can continue lumping all drugs together". After two years' research, the WHO panel determined that in the long term, cannabis has fewer effects on health than either tobacco or alcohol in five out of seven categories, and carries only a marginally higher risk in the other two.
But the WHO cut that section from a report last December into the harmful effects of cannabis, following pressure from the US's National Institute on Drug Abuse (Nida).
One of the panel members, Billy Martin of the Medical College of Virginia, based in Richmond, said yesterday: "I wasn't involved in those discussions, but I know WHO talked to Nida after our draft was submitted." Nida has been a consistent opponent of moves to decriminalise cannabis use in the US, citing various experimental studies which seem to show harmful effects from using the drug.
Dr Martin explained that the panel wanted to provide data which would compare the effects of cannabis if it were as readily available as alcohol or tobacco. "We wanted to do a qualitative comparison, rather than a quantitative one. With society as it is, its effects are clearly no worse than those other two drugs." But that is a distorted comparison, because criminalisation means fewer people regularly use cannabis.
The panel investigated research on the effects of the three drugs. Topics included harm to the foetus if used by pregnant mothers, tendency to promote violent behaviour, tendency to cause dependence, withdrawal effects, and effects on brain function. In all these cases, cannabis was found to be less harmful than tobacco or alcohol.