Smoke without fire? Scaremongering by the British Lung Foundation over cannabis vs tobacco

by Professor David Nutt

The BLF is an admirable charity that promotes lung health and supports those
affected by lung disease. Unfortunately, last week they produced a press release

promoting unfounded claims about the harms of cannabis to the lungs. These
claims were uncritically parroted from this press release as ?news? by the BBC
, Channel 4
Sky , the Independent
Evening Standard
the Huffington Post

and more.

The BLF, who wish to promote awareness of ?the serious, even fatal impact
[cannabis] can have on the lungs?, managed to hit the headlines with a survey
about public attitudes to cannabis commissioned alongside their new report
existing evidence. Surveys, with their (often unsupported) appearance of
objectivity, are a popular way for groups, commercial or otherwise, to win press
attention. It has worked for them before – the Daily Mail has a ten-year old

archived online reporting a virtually identical story of BLF ?research?
apparently showing that the dangers of cannabis are underestimated, and worse
than tobacco. The, as now, the BLF received news coverage as if they had made a
breakthrough just through publishing a survey and a report of evidence
Confusingly, whilst this is the BLF’s second special report on cannabis, they
have never dedicated a special report to tobacco, which causes the vast majority
of lung cancer deaths and many other lung conditions.

This time around, the BBC, whose science coverage usually deserves praise,
rehashed the first lines of the BLF?s press release, writing ?88% [of the
public] incorrectly thought tobacco cigarettes were more harmful than cannabis
ones – when the risk of lung cancer is actually 20 times higher?. In this
sentence, as in almost every news article I have seen on the subject, almost 9
in 10 of the public are condescended to as being mistaken, but where is the
evidence for this assertion that tobacco is so much kinder to the lungs than
cannabis? Could the public perhaps be wiser about drug harms than the BLF and
the media? I had a closer look at the BLF?s report to check their evidence.

The BLF?s report itself references a great deal of scientific evidence, but it
seems to be an attempt to collect evidence that supports their predetermined
opinion that cannabis harms the lungs, rather than exploring the evidence to
find out what the balance of findings really suggests. When the evidence they
found was mixed, they came to firm conclusions that the most alarming
interpretation of the most alarming evidence was true. This is most striking in
the case of the lung cancer claim that tops the press release, that a cannabis
joint is 20 times as carcinogenic as a cigarette. This is an old chestnut,
listed amongst Wikipedia?s list of popular drug myths
But that didn?t stop Kenneth Gibson of the Scottish National Party lodging a
for S4M-03197) in the Scottish Parliament last week on 8th June endorsing the
BLF?s claims and recommendations.

This claim about the 20-fold cancer risk is prominent in the introductory
?background? information section of the BLF?s report. Here it assures the reader
that the evidence explored in the report (section 3.2) shows this. But the
report contradicts itself: Section 3.2 on cancer actually very reasonably says
that ?studies in human populations have yielded conflicting evidence on the
subject: some suggest there is a link between smoking cannabis and lung cancer
while others don?t [3 references]. It?s worth noting that these studies are of
limited value as they looked at relatively small numbers of people and didn?t
take into consideration the quantity of cannabis smoked or the effects of
smoking a mixture of tobacco and cannabis. In addition, some previous evidence
suggests that THC may have anti-carcinogenic effects?.

Having explained, with directions to three references, that the evidence is
mixed and inconclusive, the report?s writer(s) disappointingly then give a long
and overgenerous account of one of the three papers referenced, a 2008 study
by Aldington (a
thorough scientific rebuttal of which can be found here
). They then dubiously
interpret the study as suggesting that a joint is as carcinogenic as 20
cigarettes. Christopher Snowdon has written a blog post

on just why this interpretation is wrong. Do the BLF at least give other
evidence an airing? After considering Aldington?s paper, a much smaller account
is given of another of their references, which says cannabis increases lung
cancer risk 2.4 times, and they do not write anything about their third
reference, which found no link to lung cancer. This last study, by Hashibe et.
al., looked at more people?s cannabis use over a longer time, and so has a claim
to be the most valid. Why did the BLF reference three studies then largely
ignore the findings of two?

We cannot doubt the BLF?s worthy intentions to help us all look after our lungs,
and indeed there are harm-reduction messages that should be heard about cannabis
smoke, specifically that if you must use the drug despite the risks, rolling
with tobacco may increase risk of harms, and that using a cannabis vaporiser
instead of smoking it may decrease harms.

The BLF?s lack of care with the evidence, and the media?s lack of care in
fact-checking, could have the opposite effect from their good intentions. Public
confidence in science as a means of getting to the truth can only be harmed when
the BBC reports ?experts? mistakenly declaring that what 88% of us apparently
think about cannabis is wrong. What?s more, if the BLF?s misguided information
is believed, people could actually be put at greater risk of lung cancer, for
example by cutting down on the cannabis in their joints and padding them out
with more tobacco, or by making parents relatively more relaxed about finding
out that their teenagers smoking cigarettes every day than finding out that they
smoke the occasional joint.

(Apologies for low res image).

What can be done? The ISCD contacted the BBC on the 6th of June, but as yet the
BBC have not replied or removed the inaccuracies although they have now included
an alternative opinion on the subject from Peter Reynolds of Clear. The Metro,
on the other hand, can be thoroughly commended for their prompt and prominent
publication of critical responses to their article from me
and other
readers. We will pursue further corrections, firstly by contacting editors
directly, and if that fails, through the PCC. I will update readers of this blog
on any progress.

The ISCD’s aim is for ordinary people, without scientific expertise, to be able
to find reliable information about the effects and risks of drugs. With
thousands of voices clamouring to be heard, each offering conflicting views,
it?s a huge challenge. As I write, the BLF?s claim about cannabis cigarettes
being more carcinogenic than tobacco ones has already found its way onto
Wikipedia?s information about cannabis harms
so Wikipedia currently reports, on different pages, the same claim as an
evidenced fact and as a popular myth. Though I trust it won?t be there long,
this shows how easily misinformation can gain the stamp of truth. The ISCD
website,, should help individuals who are looking for
evidence-based information. Our drugs information page on cannabis provides
scientifically evidenced information on the drug and its effects and harms. For
information on the specific connection between cannabis and cancer, see Cancer
Research UK?s balanced information

We gave the BLF the opportunity to address the inaccuracies and inconsistencies
of their report which they declined, thus missing an important opportunity to
address the very real harms of smoking. Public health organisations are to be
commended for trying to help the general public make better choices.
Unfortunately in this case, the choice made was to confuse rather than inform.

*Professor David Nutt
* | June 11, 2012 at
3:07 pm | Categories: Uncategorized
| URL:


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