The row over the sacking of Professor David Nutt is, it seems, rumbling on nicely with this exchange between Evan Harris and Alan Johnson in regards to the accuracy, or otherwise, of comments made by Johnson in his statement to the House of Commons:

The exchange contains this classic example of politician, Johnson, answering the question he’d have preferred to have been asked, not the one he was actually asked:

Evan Harris:

5. You stated: “My final point is about what Professor Nutt did last week at King’s College; incidentally, he was opposed by Professor Robin Murray, the head of psychiatric research, who takes a completely different view.”

This is incorrect. As we saw above, the King’s College event was four months ago not last week. Professor Robin Murray was not there.

Alan Johnson:

5. Professor Robin Murray did, indeed, oppose Professor Nutt’s comments. These were made in the Guardian on 30 October and Professor Murray does take a different view on cannabis to Professor Nutt.

Johnson was sloppy in making his statement to the House, not only in getting the date Nutt’s lecture at King’s College completely wrong but in referring to Prof. Robin Murray is a way which implied that he had been present at the lecture and had spoken in opposition to Nutt’s position.

Interestingly, in response to this point, Johnson makes yet another sloppy error of fact – Murray’s commentary on Nutt’s Guardian article of 29th October 2009 was also published on the 29th October 2009 at 5:30pm at 5:30pm, a matter of three hours after Nutt’s commentary and not the following day as Johnson claims in his reply to Harris.

Murray has rapidly become the politician’s favourite cannabis expert due to his trenchant views on its association with schizophrenia and other psychotic disorders. He is also, it sad to say given his status as an otherwise respected acadmic, not above grossly misrepresenting the past work of David Nutt and other members of the ACMD:

The Advisory Council on the Misuse of Drugs (ACMD), on which Professor David Nutt sits, has an unfortunate history in relation to cannabis. In 2002, it boobed by advising David Blunkett, then home secretary, that there were no serious mental health consequences of cannabis use; the council had done a sloppy job of reviewing the evidence. Since that time, they have been trying to regain credibility, and now accept that heavy use of cannabis is a risk factor for psychotic illnesses including schizophrenia.

In truth, the ACMD’s 2002 report on the classification of cannabis did nothing of the sort:

4.3.7 Acute cannabis intoxication can also lead to panic attacks, paranoia and confused feelings that drive users to seek medical help. These effects are generally short lived and usually respond to reassurance or a minor tranquilliser. In some cases acute cannabis intoxication can produce a psychotic state that may continue for some time and require treatment with antipsychotic drugs. This is similar to the psychotic states following intoxication with cocaine or amphetamines. In a few cases such an episode may be the start of a long-lasting psychotic illness, usually schizophrenia (see below). In people with pre-existent mental illness, especially schizophrenia, acute cannabis use can aggravate the condition…

4.4.6 The other main concern about the chronic use of cannabis is whether it can lead to mental illness (especially schizophrenia). Although debated for well over a century, no clear causal link has been demonstrated. The onset of schizophrenia often occurs in the late teens, when cannabis use is most common, so that an association is inevitable. This does not, though, necessarily mean that the relationship to cannabis is causal. To make the interpretation of such findings more difficult, many of these individuals have used other drugs such as amphetamines that may also precipitate schizophrenia. Moreover, as discussed in paragraph 4.3.7, cannabis intoxication can itself lead to psychotic symptoms that may be mistaken
for schizophrenia.

4.4.7 On the other hand cannabis use can unquestionably worsen schizophrenia (and other mental illnesses) and lead to relapse in some patients. Its use should therefore be particularly discouraged in all people with mental health problems. We do not know why those with schizophrenia use cannabis when it can make their condition worse. It may be cultural or related to peer pressure; but it is also possible that cannabis helps deal with some aspects of the illness, or possibly ameliorates some of the adverse consequences of their medication.

In a slightly more informal vein, a 2007 article in the Guardian, at the height of the ‘reefer madness’ scare, offered this information/advice on the effects of cannabis on mental health to a 39 year old who had become concerned that her recent bouts of anxiety and insomnia might be related to her past use of cannabis:

The risk of smoking cannabis is a bit similar to that of drinking alcohol. Most people who drink alcohol, and most people who smoke cannabis, don’t come to any harm. However, just as drinking a bottle of whisky a day is more of a hazard to your health than drinking a pint of lager, so skunk is more hazardous than traditional forms of cannabis, such as herb or resin, because it may contain three times as much of the active ingredient tetrahydrocannabinol (THC).

The adverse effects of cannabis use are different to those you describe. They usually start with either memory difficulties or paranoid and suspicious ideas, and can progress to psychotic symptoms such as hallucinations and delusions. These symptoms usually come on while the individual is still smoking, and there is no good evidence that smoking cannabis can cause either anxiety or insomnia.

That seems to offer pretty much the same view as that advanced in the 2002 ACMD report, doesn’t it? So its interesting to note the name of the individual who’s opinion this is:

Professor Robin Murray works at the Institute of Psychiatry

Oops…

One bout of misrepresentation could be happenstance, but what about two, as Murray goes on to state that:

Professor Nutt states that, in 2007, the ACMD were asked to review the situation again because “supposedly, skunk use had been increasing and it was getting stronger”. In fact, the ACMD itself concluded that street cannabis was getting more potent and a Department of Health survey has shown that skunk has been taking an ever-larger share of the market.

What Nutt actually wrote was:

The Advisory Council on the Misuse of Drugs (ACMD) was requested by the home secretary in 2007 to review the status of cannabis because: “Though statistics show that cannabis use has fallen significantly, there is real public concern about the potential mental health effects of cannabis use, in particular the use of stronger forms of the drug, commonly known as skunk.”

So, there was a skunk scare. Cannabis had gone from class B to C, but, supposedly, skunk use had been increasing and it was getting stronger, so we were asked to review whether the decision to go from B to C was still appropriate.

This followed a review in 2005, ordered by Charles Clarke, which concluded that:

The extent to which the potency of cannabis products, as used by consumers, has increased over the past few years is unclear. The available evidence is based solely on material seized by law enforcement officers. This suggests that, while the potencies of cannabis resin and “traditional” imported herbal cannabis have remained unchanged over the past 10 years, the average potencies of sinsemilla seizures have increased more than two-fold. There is, however, too little information about the potency and pattern of use of cannabis products by consumers. Further research in this area is also urgently needed.

As a result, it was only after a further review was requested in 2007 that the new evidence on patterns of use and the increased THC content of skunk were considered by the ACMD’s technical committee, but not, as the minutes of its meeting in November 2007 show, until February 2008:

Agenda Item 7. Cannabis Review Update

7.1 The Chair stated that, as the Council is aware, the Home Office has asked for a review of the classification of cannabis. A steering group has been convened to bring together the meeting and work programme. The Council will hold a 2 day evidence gathering meeting in February; the first day of which will be in public and the second in private for consideration of the evidence and deliberations. The report will be presented to the Home Secretary in April.

And it was only during that review that the ACMD were able to conclude, from the evidence that:

10.6 The available evidence therefore confirms that sinsemilla now appears to dominate the cannabis market and to have a substantially higher THC content than cannabis resin or traditional herbal cannabis and minimal quantities of CBD. Whether THC content of cannabis resin, traditional herbal cannabis or sinsemilla has changed since our previous report is less clear because the results of the analyses in Tables 6 and 7 represent results from heterogeneous samples.

And they were also able, finally, to arrive at a conclusion on the alleged causal relationship between cannabis and schizophrenia:

12.8 The evidence to support an association between the use of cannabis by young people and the development of a psychotic illness (including schizophrenia) is not entirely consistent (Section 8). There is a significant increase in the risk of the development of a psychotic illness (including schizophrenia) in controlled observational studies (Section 8.7), but this does not appear to have been accompanied by an increase in the incidence of psychotic illness or schizophrenia at a population level (Sections 8.9 and 8.10). This may reflect a weak and complex causal link, or some other factor(s) such as a common predisposition to schizophrenia and also to cannabis use. Miller and colleagues reported that individuals at high risk, because of a family history of schizophrenia, appeared to be susceptible to cannabis-related illnesses if they had a history of certain behavioural problems between the ages of 13 and 16 years.

12.9 On balance, the Council considers that the evidence points to a probable, but weak, causal link between psychotic illness and cannabis use. Whether such a causal link will become stronger with the wider use of higher potency cannabis products remains uncertain.

Far from back-pedalling on their 20o2 conclusions in order to save face, the ACMD have done no more than follow the evidence in each of their reviews, taking into account any new data that may have emerged in the period between reviews.

For good measure, Murray also tosses in this criticism of the ACMD’s data on trends in the incidence of schizophrenia:

Professor Nutt claims that the incidence of schizophrenia is falling while consumption of skunk has been rising. Sadly, the paper he points to is a study of diagnosis in general practice and we know that GP records on psychosis are far from accurate. The only good longitudinal data on the incidence of schizophrenia in the UK comes from south London, where the incidence doubled between 1964 and 1999. There are probably several factors contributing to this but abuse of drugs is likely to be one.

Murray, in a fit of modesty no doubt, fails to mention that the ‘good longitudinal data’ comes from the Maudsley Hospital in Camberwell, where he’s an honorary consultant psychiatrist in addition to his position as Professor of Psychiatric Research and that the data he’s referring to is from a paper on which he is cited as a co-author:

As for which provides the more reliable picture of the prevalence of schizophrenia, the research commissioned by the ACMD in 2008 has since been published in a peer reviewed journal with an abstract that notes that:

Retrospective analysis of the General Practice Research Database (GPRD) was conducted for 183 practices in England, Wales, Scotland and Northern Ireland. The study cohort comprised almost 600,000 patients each year, representing approximately 2.3% of the UK population aged 16 to 44. Between 1996 and 2005 the incidence and prevalence of schizophrenia and psychoses were either stable or declining. Explanations other than a genuine stability or decline were considered, but appeared less plausible. In conclusion, this study did not find any evidence of increasing schizophrenia or psychoses in the general population from 1996 to 2005.

By way of contrast, Murray’s paper is based on longitudinal data from a single hospital (Maudsley) serving an area with a population that is markedly atypical compared to the rest of the UK.

Brixton and Lewisham make up a sizeable chunk of the Maudsley Hospital’s catchment area, which means that – for starters – around 21%% of the local population are African-Caribbean, compared to 10% for London as a whole and a mere 2% for the whole of the UK, a population which exhibits significantly higher incidence rates for psychotic disorders, including schizophrenia, for reasons that are extremely complex and difficult to unpick.  There are also significant, long-standing, question marks against the reliability of schizophrenia diagnoses, particularly those made prior to the publication of DSM III in 1980, although studies conducted as recently as the late 1990s exhibit significant problems that could easily act as confounding factors in Murray’s research:

METHOD: … All in-patients on four wards at the Maudsley hospital were approached for the study; 66 participated: 24 White, 29 Black African- Caribbeans and 13 Blacks from other countries of origin. F.W.H., a Black Jamaican psychiatrist, conducted his standard clinical assessment and performed the Present State Examination (PSE) on these patients. His diagnoses were compared with the case note diagnoses made by British psychiatrists, and with the PSE CATEGO diagnoses.

RESULTS: Of 29 African and African-Caribbean patients diagnosed with schizophrenia, the diagnoses of the British and the Jamaican psychiatrists agreed in 16 instances (55%) and disagreed in 13 (45%). Hence, interrater reliability was poor (kappa = 0.45). PSE CATEGO diagnosed a higher proportion of subjects as having schizophrenia than the Jamaican psychiatrist did (chi 2 = 3.74, P = 0.052).

CONCLUSIONS: Agreement between the Jamaican psychiatrist and his UK counterparts about which patients had schizophrenia was poor. PSE CATEGO may overestimate rates of schizophrenia.

Interestingly, the two doctors diagnosed about the same number of people as having schizophrenia, but disagreed significantly over which ones.

According to abstract of Murray’s paper, his data was controlled for age, sex (gender) and ethnicity – although whether that takes into account the complex issues surrounding the prevalence of schizophrenia in the African Caribbean population is entirely unclear – but not other potential confounding factors, particularly social class and the chronic stress of poverty, both of which are likely to be significant factors given the area of London served by the Maudsley hospital.

For all that Murray is the current flavour of the month amongst politicians, because he’s telling them more or less what they want to hear, many of the arguments he deployed against David Nutt appear not to stand up to close scrutiny and, in some cases, to be as much a misrepresentation of Nutt’s position as anything that Alan Johnson or Ann Widdecombe has said over the last week.