Media Peddle Tired Cannabis Cancer Myth

In an extremely deceptive piece in the Independent and several of the UK papers today, The British Lung Foundation have been allowed to peddle a very tenuous claim that smoking cannabis poses a greater lung cancer risk than smoking the government’s tobacco cash cow.

Dame Helena Shovelton, BLF chief executive is quoted in the Independent as saying:
“Young people in particular are smoking cannabis unaware that each cannabis cigarette they smoke increases their chances of developing lung cancer by as much as an entire packet of 20 tobacco cigarettes.”

This is a curious increase on their old claim that 3 joints are equal to 20 cigarettes [1].

Both of these statements are oversimplified and counterintuitive to the majority of the scientific data. Unless they’ve been treated with obscene amounts of pesticides, Marijuana buds that are hand rolled by weed smokers are a far-cry from the mass produced chemical laden, poison filled, preservative stuffed and radioactive packs of cigarettes bought from the shops.

Cannabis simply does not contain the arm-long list of dangerous cancer causing additives that cigarettes do.

Dr. Melamede from the University of Colorado, Colorado Springs, USA, writes that cannabis smoke is also very different from tobacco smoke when inside the body.

While nicotine [from cigarettes] and THC [from cannabis] can act on related cellular pathways, they bind to different receptors to activate these pathways. The cells of lungs and the respiratory passages are lined with nicotine receptors, but do not appear to carry THC receptors. This explains why cannabis smoking has not been associated with lung cancer, a main cause of death from cigarette smoking [2].

The obvious question to ask is if the BLF’s claims are true where are all the deaths? A widely cited report by the Independent Drug Monitoring Unit states that there are at least 3 million cannabis smokers in the UK [3] (with some estimates higher and lower), and the general consensus is that there are about 9 million tobacco smokers [4].

National mortality statistics note that around 100,000 people die each year from illnesses directly linked to smoking cigarettes [5]. 42,800 are from smoking-related cancers, 30,600 from cardiovascular disease and 29,100 die slowly from emphysema and other chronic lung diseases [6].

So what amount of deaths are linked to smoking cannabis? None!

There are zero reported deaths linked to smoking cannabis each year. While it’s possible there are some here and there, they don’t make any recognized list and are clearly not on the scale of tobacco-related deaths, even though there are millions of cannabis users. If there were lots of deaths linked purely to cannabis (as opposed to those that smoke it with tobacco), don’t you think the likes of the Independent would have reported such facts in their article?

At one time the Daily Mail ran with the headline Cannabis ‘kills 30,000 a year’, but rather than sourcing the deaths directly it was simply a maths sum of how many pot smokers should be dying each year if cannabis is as bad or worse than tobacco, not that 30,000 were actually proven to be dying each year.

The BLF’s claim is based on a revamped version of a report they published 10 years ago, which they used to claim 3 joints were as dangerous to the lungs as 20 cigarettes. The new Impact of cannabis on your lungs paper is now being cited to claim 1 joint is equal to 20 cigarettes.

The Independent notes at the beginning of their article:

“The UK’s most popular illicit recreational drug is used by more than a third of people under 24, but 88 per cent believe it is less dangerous than tobacco. One in three said it did not harm health…The British Lung Foundation, which commissioned the survey, said the findings were ‘alarming’.”

Well just because they found it alarming, doesn’t mean that it is. Despite what lobbyists and Government bureaucrats might claim, the current scientific evidence shows cannabis to be relatively harmless if used recreationally by adults without underlying medical and mental health issues, and a very positive form of pain relief and medicine for many illnesses. Using basic death statistics, alcohol and tobacco are far more dangerous that pot, but are legal and a huge source of taxation.

David Nutt former head drugs adviser was sacked for making this obvious statement. Professor John Beddington, the government’s chief scientist backed Nutt, saying the evidence to support the claim was “absolutely clear cut” [7]. Despite these two leading experts stating the self-evident facts, politicians unsurprisingly have taken the political rout rather than the scientific one.

Origins of the Myth

In 2002 the British Lung Foundation released a report entitled A Smoking Gun, that compares the health risks of smoking tobacco to cannabis. Rather than new scientific data, the authors simply interpreted studies already conducted over the years.

The original claim that 3 cannabis joints equates to 20 cigarettes was a crude deception, and the BLF themselves sensationalized their own report to the media.

The data for the claim appears to be taken mainly from two papers published in 1987 [8], Tashkin, DP, Coulson, AH, Clark, VA, et al and Gong, H, Fligiel, S, Tashkin, DP, Barbers, RG, but these papers themselves did not make the explicit claim and did not make any numerical link between joints and cigarettes. Rather the BLF decided to play word games and present their own more severe conclusion to the press. As this was reported and exaggerated by the media, and other papers cited the BLF, the myth has spread without anyone bothering to trace back the source material.

The two 1987 studies on which the claim is based examine only a limited range of respiratory illness symptoms, and did not estimate the risks of lung cancer and emphysema.

To reiterate the original studies cited by the BLF to back up their claims that smoking cannabis puts you at a higher risk of developing lung cancer than cigarettes, didn’t actually make a conclusion on the link between cannabis and lung cancer!

In its report the BLF use political semantics to brush this glaring flaw under the rug, claiming that there are “conflicting findings” on the link between lung cancer and cannabis, and more research should be undertaken “to establish what link” there is. Given that the data used doesn’t actually cover the main risks, and the link between these major risks is acknowledged to be uncertain by the BLF, it is dishonest to allow the claim about cannabis and lung cancer to hit the mainstream media. Yet today, almost 10 years later the Independent and BLF spokespeople are still making the claim, and have increased the severity of it.

In their latest report the BLF put most of their eggs in a 2008 study that looked at just 79 lung cancer patients [9]. While it did conclude that “long-term cannabis use increases the risk of lung cancer in young adults,” it was strongly criticized by the European Respiratory Journal, who said the conclusion was “inadequately supported by the data”, and the study demonstrated “several methodological flaws”:

First, Aldington et al. 1 argue that the risk of lung cancer increases linearly by 8% per pack-yr smoked, based on the assumption that cancer risk from cannabis smoking is similar to cancer risk from tobacco smoking, which also increases linearly with pack-yrs. However, their own data show that the cancer risk from tobacco smoking does not increase linearly, but rather geometrically, rendering the assumption invalid. Furthermore, the authors found an increased risk of lung cancer only in the highest tertile of cannabis smokers, rendering the posited linear relationship inappropriate.

Secondly, since over half of the subjects were >50 yrs of age, it seems misleading to refer to them as “young adults”.

Thirdly, although the study is powered at 80% to detect an odds ratio (OR) of 2.4 for lung cancer in the 15% of the population who smoke cannabis, it is only the considerably smaller population that had smoked >10.5 joint-yrs that showed an increased risk. Epidemiological data on the percentage of the population that has smoked >10.5 joint-yrs are not available, but if the sample provided by Aldington et al. 1 is representative, the figure is only 4.5%. Therefore, the study is underpowered at 25% for an OR of 2.4 and 31% for an OR of 2.7. A sample of 12,000 cases and 50,000 controls would be required to detect, at 80% power, a relative risk of 1.08 per joint-yr reported by the authors. Consequently, their conclusion is probably only a chance finding.

Fourthly, although the study is termed “case–control”, the cases are adequately matched with controls only for sex. Subjects in the case group were disproportionate in age, education, wealth, heritage and smoking history; all of which are independent risk factors for lung cancer.

With that in mind, Aldington et al. 1 dismissal of a much larger study of 2,252 subjects by Hashibe et al. 2 in 2006, which found no increase in cancer risk, even in those patients who smoked >60 joint-yrs on the grounds that controls were matched for neighbourhood is puzzling, because controls should be matched for neighbourhood.

Finally, an observational study such as Aldington et al. 1 cannot establish causality, only correlation. Even presupposing that the study was methodologically impeccable, the strongest conclusion that could be drawn would be that “long-term cannabis use is associated with an increased risk of lung cancer”, not that cannabis use causes lung cancer.

What Science Says

Other than this flawed 2008 study that the BLF clamored to cite after 10 years of nothing to corroborate their agenda, other studies that have looked at links between cannabis and lung cancer have concluded that there is no direct link! Even a 2012 study (omitted by the BLF) concludes that “…analyses of pulmonary function and lung disease have failed to detect clear adverse effects of marijuana use on pulmonary function.”[10]

Hashibe et al carried out an epidemiological analysis of marijuana smoking and cancer. A connection was not observed [11]. These conclusions are reinforced by Tashkin et al who were also unable to demonstrate a cannabis smoke and lung cancer link [12]. As noted by the CLEAR Cannabis Law Reform group: “Extraordinarily, although the BLF report references a great deal of Dr Tashkin’s work, this, the most significant study of all, is not mentioned.”

Tashkin, a UCLA researcher funded by the National Institute on Drug Abuse, did a case-control study in 2006 comparing 1,200 patients with lung, head and neck cancers to a matched group with no cancer. Even the heaviest marijuana smokers had no increased risk of cancer, and strangely actually had less of a risk of cancer than non-smokers.

[Tashkin] was surprised to discover that those who smoke cannabis alone develop fewer cancers and less COPD than those who smoke nothing at all and those who smoke cannabis with tobacco do better than those who smoke tobacco alone. He concluded that cannabis provides some protective effect against lung damage and particularly the carcinogenic effects of tobacco smoke.

One possible explanation for the new findings, he said, is that THC, a chemical in cannabis smoke, may encourage aging cells to die earlier (a process known as apoptosis) and therefore be less likely to undergo cancerous transformation.

Tashkin is backed up by an earlier 1997 study by researchers at the Kaiser-Permanente HMO [13]. They monitored nearly 65,000 patients for nearly a decade, comparing cancer rates among non-smokers, tobacco smokers, and marijuana smokers. Tobacco smokers had massively higher rates of lung cancer and other cancers. Marijuana smokers who didn’t also use tobacco had no increase in cancer risk, and in fact their rates of lung and most other cancers were slightly lower than non-smokers.

This suggests that far from being more prone than cigarettes to cause lung cancer, cannabis may in fact lower the risk of lung cancer!

THC Cures Cancer?

Not only does smoking cannabis possibly protect you from cancer, but Marijuana’s active compound THC and other chemicals within the plant, administered in a variety of other ways has been found to actually slow down numerous cancer types directly.

– Researchers at Harvard University tested the compound with both lab analysis and studies where mice were injected. They found THC cuts tumor growth in common lung cancer in half and significantly reduces the ability of the cancer to spread [14].

– A 2007 study showed THC’s ability to inhibit aggressive breast cancer cells [15].

– In 2009 it was revealed that Cannabis cannabinoids have been found to stop prostate cancer cells from growing in the laboratory [16].

– Research led by Dr Wai Man Liu, at Queen Mary’s School of Medicine and Dentistry, showed that THC has the potential to be used effectively to destroy leukemia cells [17].

– Similar results have been found with Giloma (brain/spine tumors) [18], and skin cancers using topical application of THC oil [19].


It’s difficult to determine why the UK mainstream media and the British Lung Foundation are so biased and sensational about presenting facts regarding cannabis and cancer. An evening on Google with basic discernment will easily turn up a wealth of studies that show the health benefits of Cannabis and the complete lack of a link between smoking the plant and lung cancer. Considering the BLF claim to be “working for positive change for the future diagnosis and treatment of lung disease,” you’d think they’d be all over findings that THC cuts lung cancer growth in half for example.

It could be just a case of mediocrity through bureaucracy. Dame Helena Shovelton who is quoted by the Independent is not a scientist or an expert, she’s a life long bureaucrat. Before joining the BLF she was Chair of the UK National Association of Citizens Advice Bureau and former Chair of the UK National Lottery Commission. What they have to do with understanding cannabis is anyone’s guess.

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