See also the briefing to launch the report, which was held at the SMC; details here.

Professor Colin Blakemore, former Head of the Medical Research Council, said:

"Cannabis use has fallen considerably since it was re-classified in 2004. Restoring it to Class B, against the advice of the government’s own expert committee, is unlikely to protect those who are most vulnerable but will increase their chance of a criminal record. The confusion over cannabis highlights the need for a proper overhaul of the present classification system, which the public neither understands nor respects."

Professor Glyn Lewis, Professor of Psychiatric Epidemiology at the University of Bristol, said:

"Even though we cannot be certain that cannabis causes psychotic illnesses such as schizophrenia, there is now enough evidence to warn people of the possible risks that cannabis poses to mental health."

Professor Robin Murray, Professor of Psychiatry at the Institute of Psychiatry, said:

"Classification is not the issue – Education is. No 14 year old knows what ‘b’ or ‘c’ means. Indeed many of them don’t regard cannabis as a drug but rather as a natural substance without adverse effects. Whatever the Government does it needs to do it alongside an education campaign that ensures that all young people understand the risks involved, particularly with the more potent varieties such as skunk. Putting the classification back to B may send a signal that reverses some of them damage done by Minsters implying that cannabis is safe. It puts us back to where we were 4 years ago. However, we smoked even more cannabis then than now. The only thing that will bring down consumption is education."

Baroness Susan Greenfield, Director of the Royal Institution, said:

"Surely the whole point of an advisory body is just that, to advise, rather than act as politicians themselves. You wouldn’t expect an expert witness at a trial to issue the verdict, nor to pass sentence.

"It is important to bear in mind that there may be issues related to cannabis use that are not directly linked to mental illness. Issues of concern are lack of motivation and reduced attention span resulting in regular users often not reaching their full potential. My own view is that it is precisely because cannabis is perceived as low risk that people may have a more cavalier attitude to taking the drug on the assumption that their brains are completely inviolate."