Examination of Witnesses (Questions 200-219)
PROFESSOR SIR
MICHAEL RAWLINS
AND PROFESSOR
DAVID NUTT
1 MARCH 2006
Q200 Adam Afriyie: You recently reviewed
the link between cannabis and mental illness. How did you determine
the weight of the new evidence compared to the original evidence
that had informed your advice in 2002?
Professor Sir Michael Rawlins:
The evidence base had changed. Between 2002 and last year, there
was a very significant change in the evidence base.
Professor Nutt: As you may well
know, a number of studies particularly from New Zealand, following
groups of children who have now grown up into their 20s, and in
Holland and Germany, raised more evidence that cannabis could
potentially cause psychotic disorders. When you have four or five
new papers suggesting that there is potentially quite a big mental
health problem, a review seems reasonable—
Q201 Adam Afriyie: Did the strength
of that new evidence warrant review, in your view?
Professor Nutt: After the 2002
report, we decided that cannabis would be a continual item on
the Technical Committee's agenda. We did take evidence from one
of the researchers, Stan Zanit, about a year before when he presented
his new data on reassessing the Swedish conscript cohort study.
We were always conscious of the ongoing research in cannabis.
Then it got to the point that there were four or five papers that
were pointing in the direction that there might be an increased
risk.
Q202 Adam Afriyie: Is this what prompted
your review? It was not the Home Secretary?
Professor Nutt: We have ongoing
reviews but the big review that Michael chaired was prompted by
the Home Secretary.
Q203 Adam Afriyie: You first published
your advice in 2002 on cannabis and mental illness. You then needed
to re-evaluate that evidence base. Does that show any weaknesses
in the system because you had to review it so soon afterwards?
Professor Sir Michael Rawlins:
No. It was an important area with more evidence about it. We did
talk about it in 2002: could it precipitate or cause schizophrenia
in vulnerable people?
Q204 Adam Afriyie: What changed?
You alluded to this in the 2002 report. Were there no experts
on schizophrenia on the panel? Are you saying the evidence just
was not there?
Professor Sir Michael Rawlins:
The evidence was not there. It was not a lack of experts. We had
psychiatrists coming out of our ears. It was just the scientific
evidence. This is a very tricky area and even now the epidemiologists
that we recruited specially to advise us, on the balance of probabilities,
think there is a causal link, but they are not 100% certain because
there are all sorts of confounding issues that bedevil the interpretation
of the evidence. One of the difficulties is, when you take the
confounding issues into account, the relationship becomes smaller
and smaller. Technically it is a very difficult area.
Q205 Adam Afriyie: It seems to imply
that the classification of drugs that we all read about from yourselves
is dependent on the timing of when you choose to undertake a review.
Professor Nutt: No. It is dependent
on the evidence. If the evidence base changes dramatically as
it did from 2002 to 2005—
Q206 Adam Afriyie: And do you make
that judgment as to whether the evidence base has changed?
Professor Nutt: No. The evidence
base did change because there were many papers published in this
area. It was not a judgment call; it was a fact.
Q207 Adam Afriyie: There was clearly
a lot of media concern and confusion when cannabis was reclassified
from class B to class C. Did this in any way influence your decision
to leave the classification the same when you looked at it recently?
Professor Sir Michael Rawlins:
Although people say there was confusion, surveys amongst school
children showed that there was not much confusion. 95 or 97% knew
that it was illegal. The confusion, if anything, was in the newspapers.
Q208 Chairman: Or in the Home Secretary's
mind because he was obviously confused as well.
Professor Sir Michael Rawlins:
I could not possibly comment.
Q209 Adam Afriyie: You are saying
you do not think there was much confusion. From my understanding,
looking at the papers at the time and from people I spoke to at
the time, there was a great deal of confusion. Some people thought
it was legal to take cannabis. Why do you think there was such
confusion?
Professor Sir Michael Rawlins:
I do not know whether there really was that confusion. We have
made it very clear in our second report that it is essential that
people understand—particularly young people—that it
is illegal. It was quite interesting, when we were having this
discussion. One of our teachers on the Council said, "That
in many ways is much more potent than you think. I am not sure
whether I am speaking correctly or not but I say to them that
if they have ever even been cautioned for possession they will
not be allowed into America." She said that had much more
impact than many other things that she teaches the children, the
fact that they might not ever be able to visit America.
Q210 Dr Iddon: One of the things
that irritates me about the cannabis debate is that if I go into
a coffee shop, as I have done but not to buy cannabis, and I have
questioned the owner of the coffee shop, he will lay out all his
different species of cannabis and tell you exactly what the THC
content is. We talk about cannabis in this country as if it is
a single substance. The fact is that the THC content of the cannabis
being sold on the street has changed. Therefore, why should we
keep talking about cannabis as a single substance? It is not a
single substance.
Professor Sir Michael Rawlins:
No, and the strength there is 10 fold whenever it has been looked
at in the material that is seized. What we do not know is what
people are buying.
Q211 Mr Flello: There are reports
in the media this morning that seem to suggest that the use of
cannabis in the US has plateaued or is starting to plateau but,
in mainland Europe, use is still on the increase. How do you feel,
if at all, the reclassification to class C has made any difference
whatsoever, given that it has continued to increase since it has
been changed to a C?
Professor Sir Michael Rawlins:
It has not increased. It has decreased. It has been decreasing
in young people since about 1998 and it is falling at about 2%
a year. That fall has continued.
Q212 Mr Flello: That is just young
people or across the board?
Professor Sir Michael Rawlins:
That is across the board, but with young people in particular
it is falling at about 1% a year.
Q213 Mr Newmark: Is there substitution
in there—ie, are they taking some other drug?
Professor Sir Michael Rawlins:
Not that we are aware of. These are figures based on self-reporting
behaviour, so we are reliant on that.
Q214 Mr Flello: Do you feel that
the reclassification to class C has had an influence on that?
Professor Sir Michael Rawlins:
If you look at the graph, we only have another year and the line
is not a very steep curve but it is going the right way. It has
not changed as a result of reclassification, but we do not know
what is going to happen.
Q215 Mr Flello: In terms of the mental
illness use of cannabis, if I may widen it slightly to all drug
abuse, what is your view on people who suffer from mental illnesses
because of drug use or people who use drugs because they have
mental illnesses?
Professor Nutt: It is a big question.
Some drugs cause mental illness. Many people with mental illness
use drugs, even though it makes them worse, and we do not understand
why. If we just focus for a minute on cannabis, the brain makes
its own kind of cannabis. In the brain there are more cannabis
receptors, targets for cannabis, than all the receptors like serotonin
and adrenalin put together. There is some evidence that during
the course of schizophrenia the brain's own natural cannabis substances
change in relation to illness. It may be that what people are
doing when they smoke cannabis is trying to restore some internal
deficiency which may make some aspects of their mental state better,
but in many cases it makes the psychosis worse. That is an example
of the sort of complexity.
Q216 Mr Flello: In terms of the classification
of drugs and cannabis as a particular example, to what extent
do you take into account the impact of people with certain types
of mental health disorders using those drugs?
Professor Nutt: It is a factor
we consider when we look at all drugs because it comes into the
personal life issue. Also it is a factor we look at in relation
to the cost to the NHS. It is counted twice.
Q217 Mr Devine: You said the drugs
make psychosis worse. Is that evidence based?
Professor Sir Michael Rawlins:
Yes. There is very strong evidence and there is no argument amongst
psychiatrists.
Professor Nutt: That is some drugs,
not all drugs.
Professor Sir Michael Rawlins:
I am talking about cannabis. In patients with schizophrenia who
are in remission, cannabis will precipitate relapse. There is
no doubt at all. Even I know that.
Q218 Mr Flello: When the ACMD met
to discuss the reclassification, were the same people on from
the 2002 ACMD meeting present at the more recent one? Were any
measures taken to exclude them?
Professor Nutt: It was very different
because we had to extend by a month the life of the previous committee
to get the 2002 report fully approved. So many were coming off.
Professor Sir Michael Rawlins:
There was a big turnover after the publication in 2002. It was
a rather different group. I cannot tell you how many. I can certainly
let you know.
Q219 Mr Flello: It was not ever an
issue to consider about making sure there were different members
on the committee?
Professor Sir Michael Rawlins:
No. A proportion will have been there previously but a significant
proportion was new members who had not been involved in the 2002
decision.
Professor Nutt: To reassure you
on the ad hoc members, we brought in a number of external
experts to bolster the committee. We really covered all the bases,
particularly the psychiatric and the epidemiology bases.
Professor Sir Michael Rawlins:
They had not been involved in the 2002 decision.
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