British doctor claims pot kills 30,000/year?

[Gooch's dad]

British scientists warn of dangers of cannabis. (http://story.news.yahoo.com/news?tmpl=story&cid=570&ncid=753&e=4&u=/nm/20030502/sc_nm/health_cannabis_dc)

That doctor needs some lessons in basic logic:


Each year tobacco causes about 120,000 deaths among Britain's 13 million smokers. With about 3.2 million cannabis smokers in the country, Professor John Henry of Imperial College London and colleagues at St Mary's Hospital in the capital calculated the pot death toll could be 30,000.

The death toll could be 30,000. Right. If the average pot smoker chainsmoked 40 joints a day! :banghead: I am just astounded that someone who got through medical school would actually suggest something so idiotic.

By his logic, he should be able to extrapolate the smoker fatality rate to those who are exposed to secondhand smoke too.

Of course, the pro-war-on-drugs crowd will jump on this as 'proof' that pot is evil and dangerous. Oy.

[Gurdur]

*sigh*
this is the very first time I am moved to remonstrate with you, Gooch's Dad. :(


Originally posted by Gooch's dad

That doctor needs some lessons in basic logic:No, maybe you should read the article.
I'm also aware of studies showing lung damage from heavy marijuana smoking. However, as the article you cite says, the necessary research has not been done in anywhere near sufficient quantity ---- and it needs to be done.
Keep in mind most marijuana smoking is without filters, unlike most cigarettes.

The death toll could be 30,000. Right. If the average pot smoker chainsmoked 40 joints a day! :banghead: I am just astounded that someone who got through medical school would actually suggest something so idiotic. First off, how do you arrive at 40 per day ? Is that your reckoning for the average cigarette consumption ?
Are you sure you have your facts right ?
By his logic, he should be able to extrapolate the smoker fatality rate to those who are exposed to secondhand smoke too.Wrong.
He was talking direct inhalation in both cases.
Of course, the pro-war-on-drugs crowd will jump on this as 'proof' that pot is evil and dangerous. Oy. So censor medicine for political purposes instead ?
No.

[Gooch's dad]

Yes, Gurdur, I know that 'more studies need to be done'. But the doctor was obviously just extrapolating from the relative number of tobacco and marijuana smokers, using the same fatality rate for both. With NO evidence supporting that connection.

As for the 40 cigarettes/day, yes, that was a guess. Most people I know that smoke go through at least 2 packs per day, so it was a rough guess. The point was the huge disparity in how much smoke they inhale, vs. pot smokers.

I would call myself a regular user of marijuana, but I take one hit every few days. I would NOT call myself a tobacco smoker, even though I have a few clove cigarettes occasionally.

One of the major reasons that tobacco is a carcinogen is that the plant seems to preferentially absorb the radioactive isotope of polonium during growth. IIRC, the radiation is beta rays, which would be easily stopped by the skin. Inside the lungs, they're like bullets punching holes in the tissues of the lungs. I've seen nothing to suggest that cannabis has the same characteristic. The British doctors proclamation completely overlooks differences such as this.

[Gurdur]

Polonium ???
Now you've given me a whole new worry in life.
:(

However as ever I shall irresponsibly ignore it. :)

Back to the topic;
my point was you were being somewhat unfair.
But how about we get Dr Rick to haul ass in here and give us the benefit of his expertise on the questions ?
:)

[Godless Dave]

According to this article (http://news.bbc.co.uk/1/hi/health/298533.stm), "cold" kills 50,000 people each year in the UK. That's 20,000 more than are killed by pot. So before they go after pot they need to do something about the climate!

And I don't even want to speculate how many people are killed by English food each year.

[Gooch's dad]

Well, if those Brits would just pay their damned weather bills on time, they wouldn't have so much cold. Look at California, and what good weather their money can buy!

[Dr Rick]

From the article: "Each year tobacco causes about 120,000 deaths among Britain's 13 million smokers. With about 3.2 million cannabis smokers in the country, Professor John Henry of Imperial College London and colleagues at St Mary's Hospital in the capital calculated the pot death toll could be 30,000."

The professor appears to have extrapolated the pot death toll from tobacco-related mortality data, an unjustifiable methodology equivalent to calculating airline-related deaths from highway mortality data.

"If cannabis caused the same number of deaths as tobacco, given the number of smokers, then you would be seeing that number of deaths"

But you don't, and that's just one clue that the assumptions underlying the professor's conclusions are erroneous.

The scientific way to determine the mortality rate from marijuana or anything else is to actually evalutate populations that engage in the behavour or variable in question and adjust for potential confounders. When that's done, the results are a bit less dramatic then what Professor Henry calculated they should be:

A study published in 1997 on over 65,000 Kaiser Permanente Medical Care Program enrollees found no excess mortality from marijuana use.

Another study published that year on a similar group concluded that marijuana use was not associated with tobacco-related cancers or with cancer of the colon, lung, skin, prostate, breast, cervix or any other site.

"They think research should also be done into its effects on the heart and respiratory system"

"They" should read the medical literature a bit more; these issues have been investigated ad nauseum: A recent large cohort study showed no association of marijuana use with cardiovascular disease hospitalization or mortality. Marijuana has phamacologic effects that could increase the risk of myocardial ischemia (heart attack or MI) and at least one study found that marijuana users were more likely to have such an event within 60 minutes of smoking cannabis thean at any other time, but the overall rate of MI's was no greater for marijuana smokers than non-marijuana smokers. Marijuana is associated with an increased prevalence of acute and chronic bronchitis, but I know of know evidence that it is associated with an increased risk of emphsema or fatal respiratory events

These findings stand in stark contrast to the overwhelming clinical evidence that tobacco smoking is associated with a markedly increased risk of various cancers, heart diseases and death and essentially invalidate Professor Henry's simple-minded way of calculating overall mortality from marijuana use.

This quote sums it all up nicely: "Doreen McIntyre, who organizes Britain's annual "No Smoking Day," dismissed the editorial as speculation and said there was no comparison between smoking the occasional joint and smoking dozens of cigarettes every day.


'Cannabis smoking and tobacco smoking are two utterly different behaviors. The volume of smoke that is being taken in is microscopic compared to the volume regular smokers inhale and that is where the risk comes from,' she said."

Rick

[Duck!]

An article on this appeared in one of the Irish daily papers today which pointed that whereas the vast majority of the 15 million smokers in Britain smoke every day at an average at 15 cigs a day, the 3.2 million pot smokers simply refers to people who have used it in the last year, including people (like me) who only smoke it the odd time, every couple of weeks or so. It also points out that pot smokers generally smoke less and less as they grow older.

So the extrapolation of 30,000 deaths simply because there's roughly a quarter as much pot smokers definitely sounds like a dodgy conclusion to come to.

That's my uneducated 2c.


Duck!

[Jesus Tap-Dancin' Christ]

Originally posted by Gooch's dad

IIRC, the radiation is beta rays, which would be easily stopped by the skin. Inside the lungs, they're like bullets punching holes in the tissues of the lungs.
That would be alpha partivles. Beta will punch through your body without caring much.

[ps418]

As was already pointed out, the premise of the doctor's agument is not only highly questionable, its clearly false. IF cannabis use is associated with the same mortality as tobacco use, THEN cannabis use may be responsible for up to 30k deaths/yr in Britain. But, as Dr Rick already pointed out, the available evidence already indicates clearly that cannabis use is not associated with nearly this level of mortality! In fact, its not even close.



OBJECTIVES: The purpose of this study was to examine the relationship of marijuana use to mortality. METHODS: The study population comprised 65171 Kaiser Permanente Medical Care Program enrollees, aged 15 through 49 years, who completed questionnaires about smoking habits, including marijuana use, between 1979 and 1985. Mortality follow-up was conducted through 1991. RESULTS: Compared with nonuse or experimentation (lifetime use six or fewer times), current marijuana use was not associated with a significantly increased risk of non-acquired immunodeficiency syndrome (AIDS) mortality in men (relative risk [RR] = 1.12, 95% confidence interval [CI] = 0.89, 1.39) or of total mortality in women (RR = 1.09, 95% CI = 0.80, 1.48). Current marijuana use was associated with increased risk of AIDS mortality in men (RR = 1.90, 95% CI = 1.33, 2.73), an association that probably was not causal but most likely represented uncontrolled confounding by male homosexual behavior. This interpretation was supported by the lack of association of marijuana use with AIDS mortality in men from a Kaiser Permanente AIDS database. Relative risks for ever use of marijuana were similar. CONCLUSIONS: Marijuana use in a prepaid health care-based study cohort had little effect on non-AIDS mortality in men and on total mortality in women.
Sidney S, Beck JE, Tekawa IS, Quesenberry CP, Friedman GD., Marijuana use and mortality. Am J Public Health. 1997 Apr;87(4):585-90.

The association between level of cannabis consumption and mortality during a 15-year follow-up was studied in a cohort of 45,540 Swedish conscripts. The relative risk of death among high consumers of cannabis (use on more than 50 occasions) was 2.8 (95% confidence interval (1.9-4.1)) compared with non-users. However, after control for social background variables in a multivariate model, no excess mortality was found. A high level of consumption of other drugs was also associated with increased mortality; the relative risk of high consumption (greater than 50 times) was 4.6 (2.4-8.5) compared with non-users. After adjustment for social background a relative risk of 1.2 (0.8-1.9) remained; for those having used drugs intravenously more than once, the relative risk was 1.6 (0.9-2.7). Among causes of death a strong predominance was found for violent death, suicide or uncertain suicide being the single most important accounting for 34.4% of all deaths. The proportion of suicides increased sharply with the level of cannabis consumption.
Andreasson S, Allebeck P., Cannabis and mortality among young men: a longitudinal study of Swedish conscripts. Scand J Soc Med. 1990;18(1):9-15.

There is a new, massive (23,000 participants) cohort study being done in New Zealand (the New Zealand Blood Donors' Health Study), that is collecting data on, among many other things, cannabis use. We'll see what results come out of that.

Patrick

[ps418]

Originally posted by Gooch's dad
The death toll could be 30,000. Right. If the average pot smoker chainsmoked 40 joints a day! :banghead: I am just astounded that someone who got through medical school would actually suggest something so idiotic.

His assumption is more basic. The Dr is just assuming that the cannabis-attributable mortality rate in those who use smoke cannabis once a year or more is exactly the same as the tobacco-attributable mortality rate in regular smokers. This is unjustifiable a priori, and empirically unsupportable.


Duck:
An article on this appeared in one of the Irish daily papers today which pointed that whereas the vast majority of the 15 million smokers in Britain smoke every day at an average at 15 cigs a day, the 3.2 million pot smokers simply refers to people who have used it in the last year, including people (like me) who only smoke it the odd time, every couple of weeks or so. It also points out that pot smokers generally smoke less and less as they grow older.

That's exactly right. The number of people who answer yes to "ever used" is always much higher than those who answer yes to "use in last year," which is always higher than "use in last month," etc., no matter what drug you consider. Probably only a small fraction of those who report use in the last year are actually regular users. Its quite ridiculous to assume that someone who smokes a joint once a year, once a month, once a week, or even once a day, will face the same risks on average as a regular smoker, who is likely to smoke 15-25 cigarettes a day, which is exactly what the argument assumes.

Patrick

[ps418]

BTW, many of the potential harmful pulmonary side effects of cannabis use (e.g. bronchitis) are due to the method of administration -- smoking. These could be avoided altogether by using some other method of administration, such as eating. In the near future, there may be sublingual THC. But for those who want to smoke, the best way to avoid those problems is to smoke the highest potency available, preferably through a waterpipe that can filter out particulates. With a high THC content, you can get the desired effect with literally 2-4 inhalations (high THC delivery rate). The worst way to abuse your lungs is by smoking low THC ditchweed that requires 20-30 inhalations of cannabis smoke (low THC delivery rate).

Patrick

[ps418]

Other claims in the article merit comment as well:

"Smoking cannabis causes chronic bronchitis, emphysema and other lung disorders,"

There is indeed a higher prevalence of bronchitis and symptoms such as cough, weezing, and sputum production in cannabis smokers. However, the evidence for an association of cannabis smoking with emphysema or other forms of chronic obstructive pulmonary disorders (COPD), a much more serious illness, is inconsistent at best, even when the analyses is restricted to very heavy smokers (several joints per day). This is in contrast to cigarette smoking, where the evidence for increased risk of COPD is undeniable. To claim without qualification that cannabis smoking causes emphysema is misleading and very probably false.

According to the 1999 NAS Institute of Medicine report Marijuana as Medicine: Assessing the Science Base (http://www.nap.edu/html/marimed/ch3.html), no compelling evidence exists to link cannabis smoking with any form of COPD, or with lung cancer. Regarding cancer, the authors write:

As of this writing, Sidney and co-workers139 had conducted the only epidemiological study to evaluate the association between marijuana use and cancer. The study included a cohort of about 65,000 men and women 15—49 years old. Marijuana users were defined as those who had used marijuana on six or more occasions. Among the 1,421 cases of cancer in this cohort, marijuana use was associated only with an increased risk of prostate cancer in men who did not smoke tobacco. In these relatively young HMO clients, no association was found between marijuana use and other cancers, including all tobacco-related cancers, colorectal cancer, and melanoma.

Regarding COPD:

A number of animal studies have revealed respiratory tract changes and diseases associated with marijuana smoking, but others have not. Extensive damage to the smaller airways, which are the major site of chronic obstructive pulmonary disease (COPD),4 and acute and chronic pneumonia have been observed in various species exposed to different doses of marijuana smoke.41,42,128 In contrast, rats exposed to increasing doses of marijuana smoke for one year did not show any signs of COPD, whereas rats exposed to tobacco smoke did.67

Chronic Obstructive Pulmonary Disease. In the absence of epidemiological data, indirect evidence, such as nonspecific airway hyperresponsiveness and measures of lung function, offers an indicator of the vulnerability of marijuana smokers to COPD.154 For example, the methacholine provocative challenge test, used to evaluate airway hyperresponsiveness, showed that tobacco smokers develop more airway hyperresponsiveness. But no such correlation has been shown between marijuana smoking and airway hyperresponsiveness.

There is conflicting evidence on whether regular marijuana use harms the small airways of the lungs. Bloom and co-workers found that an average of one joint smoked per day significantly impaired the function of small airways.15 But Tashkin and co-workers146 did not observe such damage among heavier marijuana users (three to four joints per day for at least 10 years), although they noted a narrowing of large central airways. Tashkin and co-workers' long-term study, which adjusted for age-related decline in lung function (associated with an increased risk for developing COPD), showed an accelerated rate of decline in tobacco smokers but not in marijuana smokers.147 Thus, the question of whether usual marijuana smoking habits are enough to cause COPD remains open.


The abstract of Tashkin's 1997 paper:

To assess the possible role of daily smoking of marijuana in the development of chronic obstructive pulmonary disease (COPD), we evaluated the effect of habitual use of marijuana with or without tobacco on the age-related change in lung function (measured as FEV1) in comparison with the effect of nonsmoking and regular tobacco smoking. A convenience sample of 394 healthy young Caucasian adults (68% men; age: 33 +/- 6 yr; mean +/- SD) including, at study entry, 131 heavy, habitual smokers of marijuana alone, 112 smokers of marijuana plus tobacco, 65 regular smokers of tobacco alone, and 86 nonsmokers of either substance were recruited from the greater Los Angeles community. FEV1 was measured in all 394 participants at study entry and in 255 subjects (65 %) on up to six additional occasions at intervals of > or = 1 yr (1.7 +/- 1.1 yr) over a period of 8 yr. Random-effects models were used to estimate mean rates of decline in FEV1 and to compare these rates between smoking groups. Although men showed a significant effect of tobacco on FEV1 decline (p < 0.05), in neither men nor women was marijuana smoking associated with greater declines in FEV1 than was nonsmoking, nor was an additive effect of marijuana and tobacco noted, or a significant relationship found between the number of marijuana cigarettes smoked per day and the rate of decline in FEV1. We conclude that regular tobacco, but not marijuana, smoking is associated with greater annual rates of decline in lung function than is nonsmoking. These findings do not support an association between regular marijuana smoking and chronic COPD but do not exclude the possibility of other adverse respiratory effects. Tashkin et al, 1997. Heavy habitual marijuana smoking does not cause an accelerated decline in FEV1 with age. Am J Respir Crit Care Med 155(1):141-8.

And a 1987 paper examining a variety of measures of lung function:


To evaluate the possible pulmonary effects of habitual marijuana smoking with and without tobacco, we administered a detailed respiratory and drug use questionnaire and/or lung function tests to young, habitual, heavy smokers of marijuana alone (n = 144) or with tobacco (n = 135) and control subjects of similar age who smoked tobacco alone (n = 70) or were nonsmokers (n = 97). Mean amounts of marijuana and/or tobacco smoked were 49 to 57 joint-years marijuana (average daily number of joints times number of years smoked) and 16 to 22 pack-years of tobacco. Among the smokers of marijuana and/or tobacco, prevalence of chronic cough (18 to 24%), sputum production (20 to 26%), wheeze (25 to 37%) and greater than 1 prolonged acute bronchitic episode during the previous 3 yr (10 to 14%) was significantly higher than in the nonsmokers (p less than 0.05, chi square). No difference in prevalence of chronic cough, sputum production, or wheeze was noted between the marijuana and tobacco smokers, nor were there additive effects of marijuana and tobacco on symptom prevalence. We noted significant worsening effects of marijuana but not to tobacco on specific airway conductance and airway resistance (tests of mainly large airways function) in men and of tobacco but not of marijuana on carbon monoxide diffusing capacity and on closing volume, closing capacity, and the slope of Phase III of the single-breath nitrogen washout curve (tests reflecting mainly small airways function) (p less than 0.03, two-way ANCOVA). No adverse interactive effects of marijuana and tobacco on lung function were found. Tashkin et al, 1987. Respiratory symptoms and lung function in habitual heavy smokers of marijuana alone, smokers of marijuana and tobacco, smokers of tobacco alone, and nonsmokers. Am Rev Respir Dis 135(1):209-16.

Patrick

[Jackalope]

Originally posted by ps418
But for those who want to smoke, the best way to avoid those problems is to smoke the highest potency available, preferably through a waterpipe that can filter out particulates. With a high THC content, you can get the desired effect with literally 2-4 inhalations (high THC delivery rate). The worst way to abuse your lungs is by smoking low THC ditchweed that requires 20-30 inhalations of cannabis smoke (low THC delivery rate).


Actually, water pipes did extremely poorly in the one study I'm aware of. They ranked lower than an unfiltered joint. Vaporizers appear to work better, but there are some caveats. See the study results:
Marijuana Water Pipe and Vaporizer Study (http://my.marijuana.com/pipestudy.php3)

The point about potency is definitely true, though.

[EvilMudge]

Hmm, I wonder if this is the same guy who produced the so called 'immortality statistic'?

Briefly, they calculated that you had a 1 in 2 chance of dying from smoking tobacco. They proceeded to publish early as they felt it was important (for healthcare reasons). However, what they actually published was that you had a 1 in 2 chance of dying, if you smoked, ie 50% of smokers will never die.

I'd take a bet on that one.:)

[ps418]

Originally posted by Jackalope
Actually, water pipes did extremely poorly in the one study I'm aware of. They ranked lower than an unfiltered joint. Vaporizers appear to work better, but there are some caveats. See the study results:
Marijuana Water Pipe and Vaporizer Study (http://my.marijuana.com/pipestudy.php3)

Eeks. You're right. Ironically, I had read that article before.

Regarding vaporizers. Since that that study was done, various new vaporizers have come to market that are thought to be better. Gieringer, who conducted the tests described in the above article, has conducted preliminary tests on one new vaporizer in the spring 2003 issue of MAPS (www.maps.org), and the results look promising. This time, the tests are are for cannabanoids and individual substances in known to be in cannabis smoke, rather than simply a cannabanoids/tar ratio.


MAPS and California NORML have completed a first, preliminary round of experiments demonstrating the feasibility of testing the Volcano vaporizer (www.vapormed.de). Conducted by Chemic Labs, this $30,000 feasibility study indicated that the Volcano does produce remarkably clean vapor containing THC and other cannabinoids. We have raised an additional $25,000 from a grant from the Marijuana Policy Project (first grant proposal rejected, second approved) and have just completed a follow-up "protocol" study conducted according to FDA standards. This is the first vaporizer study designed to detect a broad spectrum of toxins in the gas phase of cannabis smoke or vapor, and will provide the necessary quantitative data to apply for FDA approval of human trials using the vaporizer. The results show that the vapor contains no detectable levels of a wide range of toxins present in marijuana smoke, but does contain substantial amounts of cannabinoids.

Vaporizer Research: An Update, MAPS 13:1, Spring 2003. (http://www.maps.org/news-letters/v13n1/13111gie.html)

Patrick

[infidelchic]

origianlly posted by Gurdur:
*sigh*
this is the very first time I am moved to remonstrate with you, Gooch's Dad :(

Sorry, but I just can't stop laughing at that sentence. Sometimes a person should just spit it out. lol

Back to your original programming.

chic

[Gooch's dad]

:D

Yeah, Gurdur made me chuckle with that one too!

-Kelly

[ps418]

Hello all,

In friday's issue of the British Medical Journal, Stephen Sidney, associate director for clinical research Kaiser Permanente Medical Care Program, explains that despite persistent popular claims to the contrary, there is no established increased risk of mortality associated with cannabis use. This is in response to the sensational claim made in the same journal in May (see the OP) that cannabis may kill as many as 30,000 a year in Britain alone (Henry et al, 2003), which in turn was based on the absurd assumption that using cannabis once a week or more has an equivalent impact on overall mortality as regular tobacco smoking.

A recent editorial in this journal implied that as many as 30 000 deaths in Britain every year might be caused by smoking cannabis.1 The authors reasoned that since the prevalence of smoking cannabis is about one quarter that of smoking tobacco the number of deaths attributable to smoking cannabis might be about one quarter of the number attributed to tobacco cigarettes (about 120 000). The idea that the use of cannabis increases mortality is worthy of closer examination. How do we assess this issue?

Firstly, we need to examine published data regarding use of cannabis and mortality. These data come from two large studies. The first study done in a cohort of 45 450 male Swedish conscripts, age 18-20 when interviewed about the use of cannabis, reported no increase in the 15 year mortality associated with the use of cannabis after social factors were taken into account.2 The second study was performed in a cohort of 65 171 men and women age 15-49, who were members of a large health maintenance organisation in California, United States. They completed a questionnaire assessing their use of cannabis, and reported no increase in mortality associated with use of cannabis over an average of 10 years of follow up, except for AIDS related mortality in men.3 A detailed examination showed that the mortality link between cannabis and AIDS was not a causal one. Thus published data do not support the characterisation of cannabis as a risk factor for mortality.

. . .

A third issue to consider is the potential relation of the use of cannabis to diseases that contribute the most to total mortality. For example, in the United States and the United Kingdom the leading cause of death is diseases of the heart, predominantly coronary heart disease, which is strongly associated with smoking tobacco cigarettes and accounts for nearly one third of all deaths. Mittleman et al noted the quadrupling of risk found in one study when cannabis was smoked within one hour before a myocardial infarction.9 However, since only 0.2% of the patients with myocardial infarction reported this exposure the number of myocardial infarctions attributable to the use of cannabis is extremely small. Cannabis does not contain nicotine, a component of tobacco that contributes importantly to the risk of coronary heart disease. Use of cannabis in a young adult population was not associated with the presence of calcium in coronary arteries—an indicator of coronary atherosclerosis10—and a cohort study conducted in a large health maintenance organisation showed no association between the use of cannabis and admission to hospital for myocardial infarction and all coronary heart disease.11

. . .

Although the use of cannabis is not harmless, the current knowledge base does not support the assertion that it has any notable adverse public health impact in relation to mortality. Common sense should dictate a variety of measures to minimise adverse effects of cannabis. These include discouraging the use by teenagers, who seem to be most at risk of future problems from drug use,12 not using before or during the operation of automobiles or machinery, not using excessively, and cautioning in people with known coronary heart disease.

Sidney, 2003. Comparing cannabis with tobacco—again. BMJ 327, 635-636. (http://bmj.bmjjournals.com/cgi/content/full/327/7416/635)

It should be pointed out that the data refuting the cannabis=tobacco assumption were readily available well before Henry et al published their editorial. Particularly, Henry et al wondered about cannabis mortality in relation to cancers, chronic respiratory disorders, and diseases of the heart and circulation, which are the 3 major tobacco-related killers. Yet, the large Kaiser Permanente cohort study (Sidney et al, 1997) found zero increase risk in cancer and circulatory disease in the cannabis-using group, and a major longitudinal study of lung function in heavy cannabis users strongly suggests that cannabis smoking does not cause the most serious chronic respiratory disorder, emphysema (Tashkin et al, 1997).

What motivated Henry et al and many other commentators was the assumption that cannabis is a lot like tobacco, and therefore it must also cause all of the health problems associated with regular tobacco use. This assumption is wrong for a variety of reasons. First and foremost is that cannabis users consume much less cannabis than tobacco users consume tobacco. Over a smoking career, a tobacco smoker may maintain an average 20 cigarette (=20 grams tobacco) a day habit. This is fairly typical. A typical cannabis smoker, on the other hand, smokes less than 1 gram a day. Even a dedicated pothead could hardly achieve a lifetime dose of cannabis equal to the lifetime dose of tobacco consumed by an average tobacco consumer.

Moreover, as it stands now, there are some compelling reasons to think that even on a per weight basis, cannabis is less carcinogenic than tobacco. Specifically, tobacco smoke contains nicotine and some very potent nicotine-derived carcinogens. For instance, nicotine and the nicotine-derived, tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) have been shown to inhibit apoptosis (programmed cell death) of airway epithelial cells via activation of an enzyme called Akt (West et al, 2003). NNK is one of the most, if not the most, potent carcinogen in tobacco smoke. Of all the known carcinogens in tobacco smoke, it is the only one that reliably induces lung tumors in all of the commonly employed animal models. It has a "remarkable" specificity for the lung, inducing adenoma and adenocarcinoma irrespective of mode of administration or animal strain used (Hecht, 1999). And remarkably, "the total dose experienced by a smoker in a lifetime of smoking is remarkably close to the lowest total dose shown to induce lung tumors in rats" (Hecht, 1999).

Thus, it is quite plausible that a major portion of the cancer risk associated with tobacco smoking is mediated by a tobacco-specific carcinogen. Nicotine itself is not a carcinogen, but can affect tumor growth and progression by inhibiting cell death (Maneckjee and Minna, 1994).

Cannabis tar also results in much less activation of CYP1A1 enzyme activity than tobacco tar. CYP1A1 is a an enzyme that converts polycyclic aromatic hydrocarbons, such as benzopyrene and benzanthracene, into active carcinogens. The activity of this enzyme is dose-dependently increased by tobacco smoke. Experiments using cultured cells in vitro show that although cannabis tar does result in increased expression of CYP1A1 mRNA, the CYP1A1 enzyme itself is competitively inhibited by THC, so that CYP1A1 enzyme activity induced by cannabis tar is only 40-50% that of tobacco tar (Roth et al, 2001).

I have put together a website focusing on the health effects, pharmacology, and medical applications of cannabinoids. You can find it here. (http://www.geocities.com/cannabinoidscience/)

Patrick

Refs

Hecht, 1999. Tobacco smoke carcinogens and lung cancer. Journal of the National Cancer Institute 91, 1194-1210.

Maneckjee and Minna, 1994. Opioids induce while nicotine suppresses apoptosis in human lung cancer cells. Cell Growth and Differentiation 5(10), 1033-1040.

Roth et al, 2001. Induction and Regulation of the Carcinogen-Metabolizing Enzyme CYP1A1 by Marijuana Smoke and delta 9 Tetrahydrocannabinol. American Journal Respiratory Cell and Molecular Biology 24, 339–344.

Sidney et al, 1997. Marijuana use and mortality. American Journal of Public Health 87, 585-590.

Tashkin et al, 1997. Heavy habitual marijuana smoking does not cause an accelerated decline in FEV1 with age. American Journal of Respiratory Critical Care Medicine 155(1), 141-1488.

Taylor et al, 2002. A longitudinal study of the effects of tobacco and cannabis exposure on lung function in young adults. Addiction 97, 1055–1061.

West et al, 2003. Rapid Akt activation by nicotine and a tobacco carcinogen modulates the phenotype of normal human airway epithelial cells. Journal of Clinical Investigation 111 (1), 81–90.

[Gooch's dad]

Fantastic post, Patrick!

:notworthy :notworthy :notworthy

[The Cromwell Institute]

Originally posted by Jackalope
Actually, water pipes did extremely poorly in the one study I'm aware of. They ranked lower than an unfiltered joint. Vaporizers appear to work better, but there are some caveats. See the study results:
Marijuana Water Pipe and Vaporizer Study (http://my.marijuana.com/pipestudy.php3)

The point about potency is definitely true, though.

Shit. I had no idea how much good bud I'd been wasting.

I wonder if an old grandpa pipe made of cherry wood would be more efficient?

[beausoleil]

Reality check:

Almost all the cannabis users I know (in the UK) smoke resin in small amounts crumbled into hand-rolled tobacco cigarettes.

They almost all smoke tobacco as well, sometimes because they got addicted from the way they smoke cannabis.

[Dylan]

Although it may be true that people who smoke marijuana also may behave in ways that are even more cruel to their bodies, I dont think there's a direct correlation between the two.

It would be an interesting study though, how many people got addicted to tobacco through its use with marijuana.