Select Committee on Home Affairs Minutes of Evidence

Examination of Witnesses (Questions 480 - 499)



  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 than that.

  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 the UK?
  (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 know—you just have to read newspapers and you learn how to use it—into 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 more addictive?
  (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 of memory.

  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 happens.

  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 marathon—it is better to watch it—then 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.

previous page contents next page

House of Commons home page Parliament home page House of Lords home page search page enquiries index

© Parliamentary copyright 2002
Prepared 22 May 2002