Strangely the Daily Mail didn’t pick up on the latest cannabis shock horror story, but not to worry because the BBC and the so-called “Independent” took up the slack

“Health risks of cannabis ‘underestimated’, experts warn” screamed BBC news (here) – oh dear, “experts” are warning about something, it must be serious. Worse, the Independent had this doom laden warning “Young cannabis users ‘do not realise the huge danger to their health'” and carried this bombshell

Cannabis smoking poses a 20-times greater risk of lung cancer per cigarette than tobacco smoking.

This, of course, from the same newspaper group that told us in 2007

The skunk smoked by the majority of young Britons bears no relation to traditional cannabis resin – with a 25-fold increase in the amount of the main psychoactive ingredient, tetrahydrocannabidinol (THC)

The Independent never lets fact get in the way of a good story and yet again – either through sloppy editing or a deliberate desire to spread anti cannabis hype – they misreported the facts. The BBC came closer when they reported this 20 times figure:

And 88% incorrectly thought tobacco cigarettes were more harmful than cannabis ones – when the risk of lung cancer is actually 20 times higher.

Spot the subtle difference? No? Read on.

The reason for all this is yet another report from the British Lung Foundation (BLF) – famous for it’s wildly alarmist 2002 report “A smoking gun” (read it here)  which  UKCIA critiqued here.  This new report is called “The Impact of Cannabis on Your Lungs” (read it here) and claims to be a scientific paper summarising the known health effects of smoking cannabis.

The paper lists a whole collection of studies most of which seem to point to dire warnings about the harms of cannabis smoking. Now at this point it’s important to make the point that cannabis smoking is not without risk. There is no doubt that cannabis smoke contains a lot of cancer causing agents, indeed breathing in any smoke is going to damage the lungs to some extent, if only because of the presence of PM10’s – solid particles small enough to penetrate the lungs. There is a simple truth, which is the less smoke you breath in the better.

However, it does seem that THC – the main constituent of cannabis – has anti-cancer properties which work to reduce the risk of cancers developing. It is, of course, entirely possible for cannabis smoke to be both cancer causing and cancer suppressing at the same time, the net result being whichever effect wins out. High potency cannabis is likely to be less carcinogenic than low potency cannabis, which would require much more smoke to be breathed in.

Ways of smoking which involve large amounts of smoke are to be discouraged; no-one is claiming that smoking cannabis is a healthy thing to do.

The BLF are making some serious claims here though, to the effect that cannabis is very much worse than tobacco, so how well do their claims stack up?:

On the evidence of cannabis causing cancer they write in some detail of studies which seem to prove a causal link between cannabis and cancer, but on studies of actual user populations

However, 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. 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..

Actually, the studies conducted by Tashkin et al were of substantial populations, why were they played down in this way and not properly discussed? Actually real life studies of cannabis using populations do not provide strong evidence of a link to cancer, if any at all.

Plus, almost in passing the BLF acknowledge the possible mechanism by which THC is acutally anti carcinogenic.

 In addition, some previous evidence suggests that THC may have anti-carcinogenic effects

There’s actually quite a lot of evidence to this effect now, so again, why play this down? Could it be because the results are so off message? This sort of thing is simply cherry picking the data, it’s close to being dishonest.

We’re being told by the BLF  there is proof that cannabis causes cancer and that it is 20 times more dangerous than tobacco. This is odd because the good old NHS tells us in its document “A summary of the health harms of drugs” from 2011 (UKCIA critique)

No cases of fatal overdose have been reported
No confirmed cases of human deaths
Cancers: no conclusive evidence that cannabis causes cancer

Although it does go on to state

cannabis use may be an important risk factor for the development of respiratory cancers but the relationship is unclear

So we have a substance that seems to have caused no deaths and with no hard evidence of being carcinogenic according to the NHS which the British Lung Foundation claim is 20 times more dangerous than tobacco. Something is not right here and the reason seems to be that the BLF is perhaps being fundamentally dishonest about another rather important issue.

It seems that what the Independent described as “cannabis smoking” and the BBC described as “cannabis cigarettes” is actually describing tobacco filled joints, which is still the normal way cannabis is used in the UK. The studies carried out by Taskin and others which the BLF  referred to in their paper which give cannabis a clean bill of health refer to the use of pure cannabis, not cannabis mixed with tobacco, as does the NHS “no cancer” information. Indeed the NHS information carried the rider

Studies of the harms associated with cannabis use are limited by confounding as many users smoke tobacco as well as cannabis, or use tobacco as vehicle for smoking cannabis resin.

Now although the BLF actually claim

• stronger evidence than ever before that smoking cannabis is linked to lung cancer;

They go on to say

• a lack of conclusive evidence on how smoking just cannabis (i.e., without tobacco) affects lung function and the development of chronic obstructive pulmonary  disease (COPD)

Which is a begrudging way of saying smoking  pure cannabis hasn’t been demonstrated as causing lung cancer or COPD, whereas of course, tobacco smoking has. The real message here is left to the last statement

• smoking both tobacco and cannabis appears to lead to a greater risk of COPD and pneumothorax than smoking  a similar amount of tobacco alone

So looking at these statements:

Smoking cannabis pure has not been shown to be strongly linked (if at all) with COPD or lung cancer. Smoking tobacco has, but smoking cannabis mixed with tobacco is more strongly linked to cancer and COPD than smoking pure tobacco. As if to demonstrate the fundamentally dishonest way the BLF have presented this argument they write again:

Current evidence is contradictory about the effect of  smoking cannabis on lung function and COPD.

But follow it up with

However,  it’s important to note that research suggests that smoking a mixture of tobacco and cannabis is linked to a greater risk of COPD than smoking a similar amount of tobacco alone. Evidence suggests that this is true for pneumothorax too.

New research provides stronger evidence than ever before to support a link between cannabis smoking and lung cancer.

So again they present a dishonest conclusion by claiming that cannabis smoking, as opposed to cannabis mixed with tobacco smoking leads to lung cancer.

If the BLF were to be honest in this report, they would be strongly advising that cannabis smokers do no mix cannabis with tobacco – the “Tokepure” message this site has been banging on about for years, that is clary the honest conclusion from the evidence they present. Actually, they do get close to doing this:

We recommend that public health education programmes be implemented to dispel the myth that smoking cannabis is relatively safe, and to highlight the adverse respiratory effects of smoking cannabis mixed with tobacco.

Now given that they seem to accept smoking pure cannabis has “not been shown” to be strongly linked to COPD or cancer it is clearly “relatively safe” compared to smoking tobacco – but or more importance is the second part where the BLF are supporting the call for a campaign similar to Toke Pure – “to highlight the adverse respiratory effects of smoking cannabis mixed with tobacco”. UKCIA agrees totally with this, it is urgently needed. It should be made totally clear that smoking cannabis is not the same as smoking cannabis mixed with tobacco, something the BLF don’t seem to understand.

Regarding the “relatively safe” issue, the BLF actually provide more proof that this is true. They give some interesting figures regarding dependence which demonstrate a bias in the way they present the data:

It is estimated that 9 per cent of cannabis users will become dependent over their lifetime. This rises to one in six for people who start using cannabis in adolescence

The equivalent risks are 32 per cent for nicotine, 23 per cent for heroin, 17 per cent for cocaine, 15 per cent for alcohol and 11 per cent
for stimulants

It’s actually true that any drug use in adolescence will lead to great degree of dependency for kids than adults, so why make the distinction for cannabis and not, say, alcohol or tobacco. This neatly distracts the reader fromt he fact that only 9% of cannabis users devleop any kind of dependence, whereas for all the other substances the rates are higher. On these figures of course, cannabis is correctly described as  “relatively safe”.

The BLF also point out the difficulty of studying prohibited substances while calling for more research. They should accept that unless cannabis use is legalised and the supply side properly controlled and regulated, proper hard research into the user population simply isn’t possible,