Examination of Witnesses (Questions 480
TUESDAY 27 NOVEMBER 2001
480. The long-term risks of cannabis are like
the long-term risks of smoking cigarettes.
(Professor Nutt) Yes; indeed. It is probably not more
481. You do not think there are schizophrenia
dangers and all of that.
(Professor Nutt) It may exacerbate schizophrenia in
some people, may ameliorate some symptoms in other people. On
balance there is probably a negative benefit in schizophrenia,
but that is not a major public health problem.
482. Does anyone disagree with that as stated?
No long-term damages other than what you get from smoking; very
damaging but obviously not mental things as well.
(Professor Henry) The long-term damages in terms of
lung damage and lung cancer are likely to be equal and possibly
greater than cigarettes. There was an illustration of two pairs
of lungs from cannabis users in the British Medical Journal recently
showing enormous holes in the lungs in people aged 25 who were
regular cannabis smokers. We do not know how this health detriment
is going to evolve with time because we are at the relatively
early stages of cannabis use in this country.
483. In terms of addictiveness would you say
cannabis is more or less addictive than nicotine.
(Professor Nutt) I would say less, judging by the
number of users who end up having trouble stopping. Most cannabis
users stop in their thirties.
484. Shall we go onto cocaine now with the same:
short-term risk, long-term risk, addictiveness?
(Professor Nutt) Short-term risk quite high in relation
to cardiovascular side effects and also to acute psychotic episodes.
Long-term risk high, particularly in terms of dependence, cardiovascular
damage and possibly psychiatric problems. Addictiveness high.
485. Physically addictive or mentally addictive
or is it difficult to separate the two?
(Professor Nutt) Harder to separate that with cocaine
than other drugs. A bit of both.
486. In terms of cardiovascular, people having
heart attacks, how many people die from cocaine abuse a year in
(Professor Henry) The latest figures were 87 for 1999,
but that had gone up from 18 in 1996, so there is a straight line
going up. We are now seeing problems from cocaine on a daily basis,
people with chest pains, occasional cases of stroke and heart
attack and it is early days, so I have no idea how it is going
to develop over time.
487. And you do not have a user base to measure
against the number of deaths in any effective way.
(Professor Henry) No.
488. Crack cocaine? Perhaps before you answer
that you could give us a little explanation as not all of us know
the difference between crack cocaine and normal cocaine, how it
is manufactured and taken.
(Professor Henry) Powder cocaine is snorted, as probably
most people knowyou just have to read newspapers and you
learn how to use itinto the nose, where it can cause local
damage. It is a very powerful constrictor of blood vessels so
areas where the concentrated substance hits directly are deprived
of blood and eventually the nasal septum, which divides the two
halves of the nostrils, can be damaged and eventually there is
a hole between the two halves of the nose. That is local damage.
Both types of cocaine have this powerful effect on the mind, which
can lead to confusion, aggression, convulsions, on top of the
euphoria which is sought. There are other effects, mainly related
to this vaso-constrictor effect, the fact that blood vessels right
through the body are tightened up to an extreme degree, blood
pressure goes very high, to dangerous levels in anyone who takes
even a so-called recreational dose. So the term Russian Roulette
can be applied because something goes wrong at a particular moment
in time, a blood vessel in the brain can burst, rupture, or the
spasm of the blood vessels in the heart can lead to a heart attack.
These stresses over years of use, not many years, but by the time
a younger person gets to the age of 30, will lead to ageing of
the blood vessels, stresses on the coronary arteries, so that
heart attack is more common. I have seen people aged 30 with triple
vessel disease which you would not normally expect until people
are in their fifties or sixties. Things can go wrong with regular
use of cocaine in terms of damage to blood vessels. Those are
the main acute medical effects. Coming to crack cocaine, all of
those blood vessel and mental effects apply to crack cocaine but
on top crack is a crystalline form of cocaine with relatively
small, about the size of a currant, so-called rocks of crystalline
cocaine base which are smoked. They are not smoked like cigarettes
or tobacco. They can be smoked in tobacco but almost always a
flame is played on the crystal and it is directly inhaled so one
can get damage to the airways, lung damage, collapsed lungs occasionally
over and above the general body effects. It seems that people
who are addicted to cocaine tend to opt for crack, possibly because
it has a more direct effect, maybe because it is cheaper, I have
not really gone into that, but the figures are quite startling.
The figures already available in this country show that there
is a much larger number of regular crack users than occasional
crack users, whereas there is a much smaller number of regular
cocaine users than occasional users.
489. Does this imply that crack cocaine is much
(Professor Henry) It would seem so, yes. This has
been alleged on many occasions, but the hard scientific evidence
is not there. However, the epidemiology seems to support it.
490. Heroin: short term, long term.
(Professor Nutt) In the short term, the danger of
heroin is that you overdose and the ratio between a dose which
will give you pain relief, a dose which will give you a hit or
a rush and a dose which will kill you is in the order of doubling.
You can die with 6mg intravenously if you are a completely naive
user. If you have gained a lot of tolerance as a street user you
might be able to take 50 or 100mg safely but the danger is overdose.
491. So 6mg could kill someone who has never
had it before and for a hard addict 50mg does not.
(Professor Nutt) Yes, that is right. There is a lot
of tolerance. People are occasionally given heroin to treat acute
myocardial infarcts and occasionally 6mg has been known to kill
people when given intravenously if they are completely naive.
There is a lot of tolerance, but the danger is respiratory depression.
The secondary dangers are that you vomit and you inhale your vomit
as a consequence of depression, basically throat reflexes. Really
those are the only dangers of heroin intravenously.
492. Apart from impurities. The biggest number
of deaths is from impure heroin.
(Professor Nutt) No the biggest number of deaths is
from respiratory depression not from impurities.
493. I thought the 40 cases in Edinburgh and
the impurities were what changed the figures.
(Professor Nutt) No. That was then a relatively small
proportion of the deaths and that epidemic has now ceased. It
was an interesting bacteriological incident.
494. Before going on to ecstasy, is it true,
as asserted to the Committee by Nick Davies of The Guardian,
that clean heroin harms neither the mind nor the body?
(Professor Nutt) Yes, I read that with interest. Clean
heroin clearly if used appropriately is safe and as he quotes
he has friends and we have seen patients who have been using heroin
for 20 or 30 years on a three to four times a day basis just to
keep their dependence at bay. Some of these are very successful
individuals. As long as you do not get the secondary complications
of heroin like hepatitis or AIDS, then heroin is quite safe provided
you do not overdose on it. You do get dependent on it, so it does
affect the mind and there is no doubt that these people are heavily
dependent but they are not physically harmed.
(Professor Stimson) A point about impurities. When
it is said that heroin is X per cent pure, it does not mean that
the other material in the heroin is not bio-active and the other
elements in it may be drugs like methaqualone or caffeine which
affect the bio-availability of the heroin. It is rare that there
are contaminants and the clostridium outbreak in Glasgow was a
contaminant. Heroin can also be taken in two ways, as can cocaine.
When heroin is injected there is an elevated risk of overdose.
Overdose is fairly rare when it is smoked and the major problems
with heroin are when it is injected and connected with the manner
of injection and the risk of blood borne infections.
495. On ecstasy could we just do short-term
risks, long-term risks and addictiveness?
(Professor Henry) May I first add one small point
about heroin? One of the reasons why people die, and I consider
it to be the most important reason, is loss of tolerance. David
Nutt has alluded to this question of tolerance where a very small
dose will kill a naive individual yet the user who is going to
a dependence clinic for help, who turns up, and is taking 750mg
per day of street heroin, that is the kind of escalation of dose,
that tolerance can be lost in a very short period of time. There
are cases of people who have run out of heroin for two to three
days and they go into withdrawal and they have a fix of the original
dose and it kills them. Tolerance is lost for certain over two
weeks, so you have to go right back to the naive dose, but a significant
proportion of that tolerance is lost very early on after discontinuing
the drug. I just wanted to clarify on that point.
(Professor Stimson) With heroin overdose, it is quite
uncommon only to find heroin. Other drugs will be used in conjunction
and the most common one would be alcohol. It is when you are taking
two respiratory depressants together and benzodiazepines. The
majority of heroin overdoses have other drugs implicated.
496. Could we just do the point about ecstasy
now, going through the same short-term risks, long-term risks,
addictiveness, which are very helpful to the Committee, to try
to scale that before I come on to the Drugs Act and the business
of how things are classified?
(Professor Nutt) John and I may disagree on this.
I personally think that ecstasy is relatively safe in the short
term. The long-term risk is to my mind unknown at present, although
as each year goes by I get relatively more sanguine about the
risk rather than less. I accept that there is still a great deal
of uncertainty about the long-term effects on the brain. In terms
of addictiveness, it is very low.
497. What are the long-term effects you read
about? Fluid draining from the spine.
(Professor Henry) Those are short-term effects. Quite
clearly it causes about 20 something deaths per year and that
is very small in terms of the large number of users. You could
even use the word minimal for the short-term risks of ecstasy
when you compare them with those of cocaine and heroin. Addictiveness
is low. The other thing is that there is emerging evidence that
it causes damage to memory processes. There are epidemiological
comparisons of users versus non-users and even more recently we
have seen studies which have followed up ecstasy users for a year
and they have shown that aspects of memory function deteriorate
during that year. Long-term use might lead to considerable impairment
498. Could we just deal with the deaths point?
We have had some differing evidence on this. Is it the drug in
the ecstasy, the MDMA which is causing the death or is it not
taking water or taking too much water? Could you break down these
deaths for us?
(Professor Henry) Very, very briefly and simply, people
are very confused why somebody should die after taking one or
two tablets of this drug. Many people take one or two tablets,
thousands of people may be taking one or two tablets and nothing
499. Two million a week.
(Professor Henry) Fair enough, that is probably the
top estimate. The reason why somebody can die after taking a very
small amount of drug is obviously not an overdose effect, it is
largely due to the pharmacology of the drug that can make them
exercise, it gives them the energy and the empathy and the euphoria
to dance for several hours. If one is running in a marathon, or
if one watches a marathonit is better to watch itthen
you will see people drinking water every two or three kilometres
in order to keep topped up and maintain their energy levels so
they can finish. Very, very few people die after running a marathon.
If they do it is most commonly hyperthermia. When somebody takes
ecstasy and does not replace fluid, their blood vessels constrict
to maintain blood pressure and they stop losing heat, their body
temperature goes up and systems fail one by one. That is why people
can die of ecstasy after exertion.