Earlier this week, I wrote about the problem of Chinese whispers in scientific papers. That is the difference between what the media says, what the press release says, what the abstract says and what the paper itself says.
Today, I came across another similar situation but with the added complication of the ‘paper’ not really being that, i.e. it is a non-peer reviewed report that looks like a paper, plus internal inconsistency about what it has to say and a difference, in some instances, between the document's claims and what the references used to support that claim say.
You may have seen the news reports; headlines like ‘One Joint 'Same Cancer Risk As 20 Cigarettes'’1 or ‘Cannabis users warned they face higher lung cancer risk’2 announced the publication of a report from the British Lung Foundation (BLF) reviewing the risks of smoking Cannabis sativa, marijuana, and detailing the results of a survey into people’s understanding of those risks.
Let’s follow the whispers backwards. The Yorkshire Post says;
‘in fact (emphasis added) the risk of developing lung cancer is 20 times greater from a cannabis joint than a legal tobacco cigarette.’
And Sky News uses the same words with;
‘in fact the risk of developing lung cancer is 20 times greater from a cannabis joint.’
The shift from possible to certain is clear from the press release from the British Lung Foundation3 which begins;
‘Risk of developing lung cancer is up to (emphasis added) twenty times greater in a cannabis cigarette than in a tobacco cigarette’
And goes on to quote Dame Helena Shovelton, BLF Chief Executive, saying;
‘each cannabis cigarette [young people] smoke could (emphasis added) increase their chances of developing lung cancer by as much as an entire packet of 20 tobacco cigarettes.’
There’s nothing unusual about that sort of escalation by the media. There’s a belief that the public can’t understand nuance so everything has to be reported as absolutes.
The report itself, however, begins by acknowledging that;
‘We know far less about the effects of cannabis smoke than the impact of tobacco smoke.’4
But, after saying that it says in the conclusions;
‘There are established links
(emphasis added) between
cannabis smoking and:
• chronic coughing;
• sputum (phlegm) production;
• legionnaires’ disease;
• acute bronchitis;
• airway obstruction;
• pneumothorax, and
• lung cancer’
I want to look at three of those ‘adverse effects’; legionnaires’ disease, aspergillosis and tuberculosis (TB).
The report states that;
‘One study shows that cannabis smokers are at increased risk of developing legionnaires’ disease.’
One study is never really enough to be able to claim an ‘established link’ unless it is a really large well-conducted study. The study cited by the BLF, however, is a case report on three cases of legionnaires disease5 that relies heavily on the fact that two of the patients were younger than the normal age for contracting this infection to make the connection between their cannabis use and their disease.
In the case of aspergillosis, the ‘established link’ is based on one case study concerning a patient recovering from a bone marrow transplant to treat leukemia6, hardly typical of the mass of cannabis users. Plus the paper finds that the cannabis the man was using was contaminated with mould meaning there is no ‘established link’ with cannabis produced under controlled conditions.
The report gives four references for TB resulting from cannabis use. All four are case studies and all four are related to unusual circumstances of cannabis use.
In Queensland, 57 people were reactors to tuberculin skin tests. 45 of them had shared the same water pipe for smoking cannabis but the paper concludes (in spite of its title ‘A cluster of tuberculosis associated with use of a marijuana water pipe’);
‘the most important risk factor for acquiring TB infection in this cluster was close household contact with a case’7
In Baltimore, an outbreak of TB occurred in a community of gay men, predominantly HIV positive, living communally and using cannabis.8 The abstract makes no suggestion that this last was the dominant factor.
Another of the cited accounts deals with the practice of ‘shotgunning’ that is transferring exhaled cannabis smoke from person to person.9 Obviously, this practice is a good means of spreading infection with or without the presence of cannabis in the exhalations.
‘Hotboxing’ refers to smoking
cannabis in a confined space, typically a car, so that exhaled
smoke can be re-inhaled by anyone in the group. It is a means of
ensuring the maximum use is made of the available marijuana.
A recently published biography of Barack Obama says that ‘hotboxing’ was his preferred method of using marijuana in his student days.11 The president hasn’t denied his student drug use but says he now realises it was wrong. That’s fine; many people regret things they have done in the past.
It would be helpful, however, if Obama would acknowledge that his luck in not being caught undertaking criminal acts means that he was able to go on to become president but, under his presidency, there are young people whose futures are being blighted because they haven’t been so lucky and are saddled with a criminal conviction for marijuana offences.
A case study from Seattle found that ‘hotboxing’ involving a group that included at least one TB carrier had caused the infection to be passed on.10
I’m really not sure I understand the motivation of the BLF. The report makes it quite clear that;
‘Although cannabis is the world’s most widely used illicit drug, there has been surprisingly little research into its effects on respiratory health.’
And then takes that ‘surprisingly little research’ and makes statements about the effects of cannabis smoking that simply cannot be supported by what evidence there is.
There is also the usual thing about cannabis being stronger these days. This the report believes means that;
‘the conclusions of many previous studies investigating the long-term effects of smoking cannabis may not be applicable to current cannabis smokers’
Yet of its 86 references 23 refer to papers that are over twenty years old.
It also includes a section on mental health and cardiovascular issues related to cannabis. This has no place in a report that is supposed to be about lung diseases and destroys any possibility of it being seen as an impartial assessment.
We know that smoking is harmful and it would be foolish to suggest that smoking cannabis, especially if done with tobacco, will not also be harmful but overstating what little evidence there is will not make people respond.
Much better to just say that there are almost certainly risks but that more research should be done to protect public health. It occurred to me that cannabis smokers might, when smoking tobacco, draw more on their cigarettes than a tobacco only smoker. I asked on Twitter if anyone knew if such research had been done but it seems not. I'm grateful to @AlexStevensKent and @TransformDrugs for the information they provided.
The truth is that prohibition, which is supposed to protect people from the harm of drugs (but doesn't), also prevents researchers from making better assessments of what those harms might be.
1.One Joint 'Same Cancer Risk As 20
Cigarettes' Sky News 4th June 2012
2.Cannabis users warned they face higher lung cancer risk Yorkshire Post 3rd June 2012
3.New report reveals dangerous lack of public understanding of the health risks of cannabis British Lung Foundation 6th June 2012
4.The impact of cannabis on your lungs British Lung Foundation 1st June 2012
5.Legionnaires Disease in Cannabis Smokers 10.1378/chest.10-0410 CHEST October 2010 vol. 138 no. 4 989-991
6.Fatal Aspergillosis Associated with Smoking Contaminated Marijuana, in A Marrow Transplant Recipient DOI 10.1378/chest.94.2.432 Chest 1988;94;432-433
7.A cluster of tuberculosis associated with use of a marijuana water pipe Munckhof, Konstantinos, Wamsley, Mortlock & Gilpin INT J TUBERC LUNG DIS 7(9):860–865
8.A multi-state outbreak of tuberculosis among members of a highly mobile social network: implications for tuberculosis elimination. Sterling, Thompson, Stanley, McElroy, Madison, Moore, Ridzon, Harrington, Bishai, Chaisson & Bur Int J Tuberc Lung Dis. 2000 Nov;4(11):1066-73.
9.“Shotgunning” as an illicit drug smoking practice Perlman, Perkins, Paone, Kochems, Salomon, Friedmann & Des Jarlais Journal of Substance Abuse Treatment - January 1997 (Vol. 14, Issue 1, Pages 3-9)
10.Tuberculosis Outbreak in Marijuana Users, Seattle, Washington, 2004 Oeltmann Oren, Haddad, Lake, Harrington, Ijaz, & Narita
11.Thanking his drug dealer in his yearbook and inventing the best ways to inhale: Book lifts lid on 'Barry' Obama's marijuana-smoking school days Daily Mail 25th May 2012