Comparing cannabis with tobacco
BMJ 2003; 326 doi: https://doi.org/10.1136/bmj.326.7396.942 (Published 03 May 2003) Cite this as: BMJ 2003;326:942
All rapid responses
While there can be little doubt that smoking anything is likely to be
detrimental to the health of one’s respiratory system, scientific data
does not support the extension of the biological consequences
resulting from tobacco smoke to marijuana smoke(1). Two
complementary pieces of information support the position that the
effects of the two, tobacco and marijuana, are different.
The irritant
properties of all smoke will naturally tend to promote a pro-
inflammatory immune response with the corresponding production
of potentially carcinogenic free radicals. However, cannabis
promotes immune deviation to an anti-inflammatory Th2 response
via immune-system specific CB2 receptors(2). Thus, the natural
pharmacological properties of marijuana’s cannabinoids, that are
not present in tobacco smoke, would minimize potential irritant
initiated carcinogenesis.
In contrast, the nicotine present in
tobacco smoke, but lacking in cannabis smoke, specifically
activates nicotine receptors in respiratory pathways that in turn
protect these cells from apoptosis normally promoted by genotoxic
agents found in smoke(3). Thus, the pharmacological activities of
tobacco smoke would tend to amplify its carcinogenic potential by
inhibiting the death of genetically damaged cells. Together these
observations support the epidemiological study of the Kaiser
Foundation that did not find cannabis smoking to be associated
with cancer incidence(4). Additionally, the demonstrated cancer
killing activities of cannabinoids has been ignored. Cannabinoids
have been shown to kill some leukemia and lymphoma(5), breast
and prostate (6), pheochromocytoma(7), glioma(8) and skin
cancer(9) cells in cell culture and in animals.
1. Henry JA, Oldfield WL, Kon OM. Comparing cannabis with
tobacco. BMJ. 2003;326:942-943.
2. Yuan M, Kiertscher SM, Cheng Q, Zoumalan R, Tashkin DP,
Roth MD. Delta 9-Tetrahydrocannabinol regulates Th1/Th2
cytokine balance in activated human T cells. J Neuroimmunol.
2002;133:124-131.
3. West KA, Brognard J, Clark AS, Linnoila IR, Yang X, Swain SM,
Harris C, Belinsky S, Dennis PA. Rapid Akt activation by nicotine
and a tobacco carcinogen modulates the phenotype of normal
human airway epithelial cells. J Clin Invest. 2003;111:81-90.
4. Sidney S, Beck JE, Tekawa IS, Quesenberry CP, Friedman GD.
Marijuana use and mortality. Am J Public Health. 1997;87:585-
590.
5. McKallip RJ, Lombard C, Fisher M, Martin BR, Ryu S, Grant S,
Nagarkatti PS, Nagarkatti M. Targeting CB2 cannabinoid receptors
as a novel therapy to treat malignant lymphoblastic disease.
Blood. 2002;100:627-634.
6. Melck D, De Petrocellis L, Orlando P, Bisogno T, Laezza C,
Bifulco M, Di Marzo V. Suppression of nerve growth factor Trk
receptors and prolactin receptors by endocannabinoids leads to
inhibition of human breast and prostate cancer cell proliferation.
Endocrinology. 2000;141:118-126.
7. Sarker KP, Obara S, Nakata M, Kitajima I, Maruyama I.
Anandamide induces apoptosis of PC-12 cells: involvement of
superoxide and caspase-3. FEBS Lett. 2000;472:39-44.
8. Sanchez C, Galve-Roperh I, Canova C, Brachet P, Guzman M.
Delta9-tetrahydrocannabinol induces apoptosis in C6 glioma cells.
FEBS Lett. 1998;436:6-10.
9. Casanova ML, Blazquez C, Martinez-Palacio J, Villanueva C,
Fernandez-Acenero MJ, Huffman JW, Jorcano JL, Guzman M.
Inhibition of skin tumor growth and angiogenesis in vivo by
activation of cannabinoid receptors. J Clin Invest. 2003;111:43-50.
Competing interests:
None declared
Competing interests: No competing interests
There are serious problems and misunderstandings with this editorial.
I would like to list several:
1. Most of the mortality risk associated with tobacco use arises from
sustained use over several decades, and the risks increase sharply as
lifetime exposure accumulates. The importance of lifetime exposure was
underlined in a major study of tobacco smokers in 2000 which found that:
"People who stop smoking, even well into middle age, avoid most of their
subsequent risk of lung cancer, and stopping before middle age avoids more
than 90% of the risk attributable to tobacco." [1]. A similar pattern
should be expected for CHD and COPD - the two other major tobacco-related
fatal diseases.
To the extent there is data on use of cannabis, it suggests that most
users (so far) quit using it in their 30s. In the OPCS Psychiatric
Morbidity Survey carried out in 1993, some 14% of adults aged 16-24 were
users, but the figure dropped to 2% among those aged 35-44, and was less
than 0.5% in people aged over 45. There may be cohort effects operating
here, and it is possible that today's young people will have longer
cannabis careers, but at present what this seems to indicate is that few
people have accumulated 20 or more years of continuous use.
The very high risks due to tobacco use ultimately arise from its
addictiveness, which causes many tobacco smokers to continue to smoke well
after they would choose to stop. Over 70% of current users say they would
like to stop, and over 80% regret ever starting: a sure indicator of
addiction sustaining long term and heavy use. As cannabis has very
different dependency characteristics (it is much less addictive) then its
pattern of use is different most users smoke less and quit earlier.
2. Completely incompatible characterisations of the user population
are used in the editorial. The figure of 13 million tobacco users is
determined by those answering ‘yes’ to the question 'do you smoke
nowadays'. In practice over 80% of these are daily users and the average
consumption is just over 15 cigarettes per day per smoker. Tobacco /
nicotine is an intensive drug-using syndrome for most of its users. In
contrast, the Home Office figure of 3.2 million users quoted for cannabis
is 'use in the last 12 months'. The figure for use in the last month (not
quoted in the editorial) is 2,062,000. The Home Office does not assess how
many use cannabis daily, but it will be very substantially less. Again
the reason is grounded in addictiveness - the lower dependency-forming
characteristics of cannabis allow for more occasional use than cigarette
smoking, which generally consolidates into a powerful addiction needing
constant attention by the user.
3. The point that THC concentrations have increased by a factor of
ten over the last twenty years is dubious as a point of fact, but more
importantly, it is completely misinterpreted. Put bluntly, a ten-fold
increase in THC concentration does not mean that modern users are ten
times as stoned as in the past. Users of both cannabis and nicotine
control their drug exposure by varying how much smoke they inhale and
retain. Higher concentrations of THC may therefore lead to LOWER smoke
inhalation for a given drug exposure. This is well understood for tobacco
(and the reason why 'light' cigarettes are such a fraud) but not well
studied for cannabis - however it is unlikely that users do not control
their intake or they would be ten times as stoned as they were 20 years
ago. Ironically, the concern raised in the editorial about different puff
volumes for cannabis (based on 1987 data, by the way) may actually have
been alleviated by the asserted increase in THC concentration in the drugs
now in use leading to lower smoke exposure as users control their dose by
taking fewer and lighter puffs.
4. The derivation of the figure of 30,000 deaths is so facile it
shouldn’t really have been written down. At this stage, there is only
limited evidence linking cannabis use to the big tobacco-related killers -
cancer, CHD and COPD. While these links should be expected, the magnitude
of the risk to the user (simply assumed to be equivalent to tobacco in the
derivation of the 30,000 figure) will depend on a variety of factors, in
particular the lifetime exposure and patterns of use - and these are very
different indeed. Very few of the 120,000 smoking-related deaths occur
in people under 40, yet hardly any of the users of cannabis are over 40 –
so who are the 30,000 dying? Given that the smoking careers differ so
much, and the usage patterns are so different, the estimate of 30,000
deaths is ridiculous. Qualifying the calculation by saying it may be ‘a
fraction’ of that adds nothing if we don’t know whether the fraction in
question is one half or one-thousandth. It does leave the media-sensitive
headline number in place and puts the figure into the public domain as the
only estimate. It is sure to be used by those with agendas other than
forming rational evidence-based insights into public health issues.
5. The case has not made that cannabis is a 'major public health
hazard' as asserted in the editorial. It is certainly not harmless and the
authors suggest several harmful effects. But there is a continuum between
'harmless' and 'major public health hazard' and simply showing there are
dangers is insufficient to place a phenomenon like cannabis on that
continuum. Most credible reviews to date have tended to suggest limited
public health impacts. For example, the Advisory Council on Misuse of
Drugs [2], concluded in March 2002 after a thorough review of the
evidence... "The high use of cannabis is not associated with major health
problems for the individual or society." There is always a need to
challenge such assessments, but any challenge has to be credible.
6. To say there is no battle against cannabis when it is a criminal
offence (even after reclassification) to use it, grow it or sell it is
absurd. I agree that more could be done to promote understanding of the
harm it causes and I hope the findings about the link between cannabis
schizophrenia, which appear to settle the question over the direction of
causation, are filtering through to users. However, one reason why health
promotion efforts sometimes fail is the lack of credibility of the
arguments presented to users. The casually fabricated mortality figure and
'war-on-drugs' rhetoric of the editorial are wholly counter-productive in
that regard. (Incidentally, the illegal status of cannabis is a barrier to
wider and better understanding of its risks because it denies
opportunities for mandatory labelling and inserts in the packaging.)
Finally, the finding that cannabis is not harmless is not new and
adds little to the important and highly-charged debate about its legal
status, which is really about societal management of personal risk and
relationship between the state and the individual. Understanding of
addictiveness and its impact on personal choice and patterns of
consumption are crucial in positioning different drugs, and entirely
absent from the analysis presented in the editorial. Sadly, editorials
like this play well in a particularly rabid section of the popular media,
which has no interest in a thoughtful societal response to all drugs based
on harm-reduction, respect for civil liberties and cost effectiveness.
Rather than fanning the flames of tabloid ignorance, the BMJ is usually a
beacon of rational and measured debate on these vital issues. I fear the
editorial guard may have been down on this one.
Clive Bates
I don't think it is a competing interest, but in the interest of
clarity I would like to disclose that I was Director of Action on Smoking
and Health (UK) until March 2003. I am writing in a personal capacity.
[1] Peto R et al. Smoking, smoking cessation, and lung cancer in the
UK since 1950: combination of national statistics with two case-control
studies. BMJ 2000; 321: 323-329.
[2] Advisory Council on the Misuse of Drugs. The classification of
cannabis under the Misuse of Drugs Act 1971, (UK Government) Home Office,
March 2002 (5.1).
Competing interests:
None declared
Competing interests: No competing interests
Masters raises an interesting question: Should scientists involved in
the cannabis debate reveal if they have ever used the drug? He mentions
his own anti-smoking work and his recovery from nicotine addiction as a
parallel. The stigma associated with nicotine is not the same as that
associated with cannabis, which may weaken the analogy dramatically.
Readers often view those who break a nicotine habit with some admiration
for a job well done. They often view those who cannot break the habit as
unfortunate victims of the tobacco industry.
Cannabis users lack this luxury because of prejudice. Cannabis
remains illegal. American public service announcements suggest that
cannabis users might kill their siblings in traffic accidents, engage in
ill-advised sexual encounters, and support terrorism. Stereotypes about
cannabis users include notions that they will soon turn to hard drugs,
that they lack motivation, and that they might have cognitive impairments.
Despite extensive data to the contrary, these stereotypes persist. Why
believe the hard work and reasoned logic of someone with impaired
cognitive abilities?
Stereotypes about abstainers also exist. Readers may view them as
drug warriors. Some may see them as eager to publish Type I errors
suggesting cannabis-induced harm. Some accuse them of being quick to
exaggerate small effects in an effort to vilify the plant.
Many cannabis debates begin with data but soon degenerate into ad
hominem arguments about personal habits. We cannot resolve problems this
way. It’s easier to dismiss someone as a pothead or tea-totaller than it
is to listen to nuanced research. But we can do it. Good peer review and
extensive discussion of detailed presentations of data, especially in
forums like this one, will definitely help.
Let science prevail over stereotypes. The cannabis debate must be
judged on the merits of the arguments rather than the actions of the
arguers.
Competing interests:
None declared
Competing interests: No competing interests
Just as I willingly acknowledge that my anti-smoking passion is
driven by 17 years of addiction to tobacco which was overcome in 1983,
should not respondents declare whether they are or were cannabis users?
Competing interests:
Please see my response
Competing interests: No competing interests
Editor, The editorial by Henry et al on cannabis is quite simply the
most unbalanced and inappropriate piece of writing on this subject I have
seen for some time. It puts together questionable assumptions, wooly
science and urban myths (such as the "potency" of modern cannabis) which
conflict with the vast majority of reputable current literature. One must
ask what the authors reasons were for this article - it could hardly have
been to educate the profession.
And, as Wodak notes, such scare tactics are not likely to do much good -
entrenching hardline prohibitionist policy will, based upon 50 years of
evidence (rather than rhetoric), only increase the damage from cannabis,
most of which stems from its prohibition, not the drug itself.
Ashton raises the issue of 8 year old smokers without, apparently, asking
how these kids come to have the drug, where their parents or teachers are,
and whether these kids may have problems apart from cannabis use which may
impact upon their health and wellbeing. Easier to blame the drug, perhaps
but that gets us.......where? More prohibition, more money spent on a
counterproductive war on drugs, and thus not on schools, welfare, equity,
justice. Even if cannabis where the cause of these kids problems, do the
current policies and practices prevent these problems (clearly, no) or
worsen them (probably, yes).
Canada, The Netherlands and many other jurisdictions have broken away from
the mesmerised trance that chanting pro-prohibition mantras induces in
many otherwise thoughtful people and institutions. Time for Britain, and
Australia, to do likewise.
Competing interests:
None declared
Competing interests: No competing interests
Ms. Brett,
If concern for our children's future is indeed your primary motive,
should you not include the harm done to our children who must now somehow
try to succeed in life now with the ball and chain of a criminal record
with them.. "Them" is our children. The "outcast" status that a criminal
record bestows on our brothers, mothers and fathers, and of course our
children, and it's effect on their future needs no study to determine how
destructive it is on their lives. It is severe. And this is obvious. There
is no controversy here. It is common sense.
I snipped your references because you referenced nothing. You gave
an opinion.....your own opinion. You stated that cannabis "impairs" the
chemical transmission system. You also inserted the word "badly". Which
study used those value judgements?. Interfering with the bodies own
chemistry or natural functions is how drugs work. All drugs. Aspirin and
caffeine for example. This interference is not inherently a bad thing, as
you seem to be suggesting.
No, it's time that reality rather than blind hysteria is brought to
the subject of drugs. For example; have you ever been given a shot of
morphine in the hospital? Did you know that heroin is in fact nothing more
than morphine that has been slightly altered so as to pass the blood:brain
barrier more quickly, providing a faster onset of the morphine? . Yes...
morphine. The heroin, once past the blood brain barrier reverts back to
morphine and from that point on, the high is indistinguishable from
morphine because it is morphine.
My point is that the demonization of heroin has succeeded in turning a
useful drug into something that no one of their right mind would ever want
to do. Well unfortunately, millions of people, and perhaps you, although
convinced that heroin will kill them and is immediately addictive, etc,
have in fact, for all intents and purposes, already done it.
That is the power of misinformation Ms. Brett. Thousands of people in
jail for doing a substance that doctors are giving to patients, in the
hospitals, by the bathtubs full, daily.
If you want to help our children, please rethink your stance on
drugs. Driving the users of the seriously harmful drugs like the
stimulants, (methamphetamine and cocaine) into back-alleys only
exacerbates the problem. Drugs will not go away using laws. Countries that
summarily execute drug-dealers or users have not stopped it. Drugs,
whether you like it or not, are here to stay. All that can be done is to
reduce the damage done. Common sense.
Sincerely,
Gary Williams
Competing interests:
None declared
Competing interests: No competing interests
To the editorial board
Dear Sir,
I was surprised at some of the things said in the recent BMJ
editorial. "Can you compare cannabis with tobacco?"
In future, when someone editorialises on such a contentious issue,
could you please ask them to declare their political allegiance. In
particular do Dr Henry and Dr Oldfield support the current practice of
criminalising cannabis smokers? Should cannabis smokers be locked up in
prison? This is an issue they ignore but it is the major public policy
used to discourage cannabis use. In fact, the editorial states that "At
present, there is no battle against cannabis and no clear public health
message." Are they unaware that unauthorised possession of cannabis is a
criminal offence? Does a 'War on Drugs' not 'battle' against cannabis?
Cannabis and Tobacco can't be compared in this way.
In a ranking of addictivity of 6 drugs both Henningfield (NIDA) and
Benowitz (UCSF) ranked Nicotine as the most addictive and marijuana as the
least addictive (comparing Nicotine, Heroin, Cocaine, Alcohol, Caffeine
and Marijuana). [Hilts, P.J. The New York Times 2-Aug-94, C3]
The writer states that "there are indications that smoked cannabis
may cause similar effects to smoking tobacco, with many of them appearing
at a younger age"
But cannabis smokers
* smoke fat less than cigarette smokers (when indulging).
* do not generally smoke everyday
* generally stop smoking as they progress out of their teens as it is easy
to stop smoking cannabis because there is no physical addiction.
While tobacco smokers:
* generally smoke at least 20 a day (when indulging)
* do smoke everyday
* often smoke for life and find it difficult to stop smoking.
It is impossible for me to understand how the writers arrive at their
'comparison', given that one of them is a consultant, specialist registrar
at a Department of Respiratory Medicine.
I'm all in favour of improving research into the harmful effects of
smoking and of discouraging the smoking of anything but scaremongering
and/or criminalisation are not the way to do it.
Competing interests:
None declared
Competing interests: No competing interests
I have contact (through North East Council for Addictions - NECA)
with cannabis users in the North East. The fact is that many young people
(including 1% of schoolchildren) do actually smoke at least 5 (up to 15)
spliffs daily and/or inhale from "buckets". Thus they obtain high
concentrations of cannabis smoke containing all the constituents of
tobacco smoke (except nicotine) including carbon monoxide, bronchial
irritants, and carcinogens. Smoking may start as young as 8 years and
more and more smokers are continuing for longer - into their 40s and 50s.
These kids do not use hash cakes or cookies as suggested by Leslie
Iverson. Figures for numbers involved not available, but NECA Counsellors
see such users daily. These young people also smoke tobacco and the
effects of cannabis and tobacco smoke on the lungs are additive.
Unlike tobacco (nicotine) cannabinoids also have adverse psychiatric
effects. A large amount of evidence shows that young and adolescent users
are especially vulnerable to these effects. Those starting to use
cannabis while in their early teens are more likely to suffer intellectual
and emotional impairment, escalate to weekly or daily use, to become
dependent, to progress to other illicit drugs, to become anxious,
depressed and suicidal and to be involved in deliquency and crime than
those starting later.
References: Fergusson DM, Horwood LJ, Swain-Campbell N. Cannabis
and psychosocial adjustment in adolescence and young adulthood.Addiction
2002; 97: 1123-35. Copeland J, Swift W, Rees V. Clinical profile of
participants in a brief intervention program for cannabis use disorders.
Journal of Substance Abuse Treatment 2001; 20: 45-52. British Lung
Foundation. The impact of cannabis smoking on respiratory health. A
smoking gun? 2002. Rey JM, Sawyer MG, Raphael B, Patton GC, Lynskey M.
Mental health of teenagers who use cannabis. Results of an Australian
Survey. British Journal of Psychiatry 2002; 180: 216-21. Swift W, Hall
Wa, Copeland J. One year follow-up of cannabis dependence among long-term
users in Sydney, Australia. Drug and Alcohol Dependence 2000; 59: 309-18.
Swift W, Hall W, Teeson M. Cannabis use and dependence among Australian
adults: results from the national survey of mental health and wellbeing.
Addiction; 2001; 96: 737-48.
Competing interests:
None declared
Competing interests: No competing interests
Professor Henry and others quite rightly draw attention to the
damaging effects of cannabis and the potential problems likely to emerge
from its increasing use.(1) There are many aspects to this debate, not
least the inevitability of the progress to further use, although other
countries have shown this to peak in young people and to deteriorate
subsequently. It is also, like most addiction problems, complicated by
there being many different side effects, some more serious than others.
Like alcohol, cannabis is likely to cause acute physical and psychological
as well as long-term damage.
Research therefore is urgently required in all these areas. Our own
recent study showed, we think, importantly, the relationship between dose
and at least some complications.(2) It makes intuitive sense that, like
other drugs of intoxication, the harmful effects of cannabis are likely to
be dose-related. The public health message, therefore, becomes like that
of illegal drugs, not geared towards total abstinence so much as
minimising the damage and diverting habitual users from the most serious
complications. Cannabis used in small quantities, that is, less than 2 or
3 grammes per day, presents quite a different prospect from more heavy use
and truly recreational (intermittent, infrequent and non-dependent type
use) must present less of a poor prognosis than dependent type use.
Patients with dependent type use, similarly to opiate and alcohol use of
this sort, are more likely to be unemployed, maringalised and in the
poorer part of the population and it is frequently our experience that
self-medication with cannabis is a control mechanism for another wise
unrewarding lifestyle.
Rather than becoming absorbed with the mechanisms for control or the
morality of use of the drug, the Health Service requires an urgent
response to another healthcare imperative, that of providing services for
the acute effects and the chronic damage caused by another largely ignored
(by the Health Service) addictive drug.
Yours sincerely
Dr Roy Robertson
References
(1)Henry, J. A., Oldfield, W., L., G., Min Kon, O. Comparing cannabis with
tobacco. The British Medical Journal 2003; 326: 942.
(2)Robertson, J. R., Miller, P., Anderson, R. Cannabis Use in the
Community. The British Journal of General Practice 1996; 46: 671-674.
Competing interests:
None declared
Competing interests: No competing interests
Numerous Discrepancies, Excessive Bias
I could write a dissertation as to why this article is the most
ridiculous piece of scientific research (if you could even call it
that)I've ever seen, but I'll get to the main points.
There are dozens of studies that refute the statement that marijuana
is harmful. It can prevent cancer as well as shrink tumors and in may
cases, even cure cancer. I've met some of these people. I recommend the
Madrid study on the inhibition of tumor angiogenesis caused directly by
cannabinoids. This is one of the few studies ever actually performed on
live test subjects, which lends itself to be far more credible than
hundreds of other studies that claim to be an accurate source. Marijuana
can also help people with chronic pain disorders, eating disorders,
cataracts, diabetes, Parkinson's, Alzheimer's and literally hundreds of
other ailments and even more symptoms of ailments.
Additionally, the article you sited for showing the obvious
correlation between mental illness and schizophrenia caused by marijuana
use, is inconclusive as to the direction of causality. If there is no
proof of causality then the source cannot automatically prove that
marijuana use causes schizophrenia. It IS however conclusive that people
who are predisposed to schizophrenia and other mental illnesses should
avoid the use marijuana or any other drugs (particularly LSD) for risk of
setting off that trigger.
Also, you stated that most cannabis smokers also use tobacco, which
you did not site. It is likely but I have not been able to find a single
study that proves it. If you have a comprehensive study on the matter I
would like to read it.
You further stated that "Tobacco smoking is responsible for 120 000
excess deaths each year in Britain, 46 000 from cancers, 34 000 from
chronic respiratory disorders, and 40 000 from diseases of the heart and
circulation. However, there are indications that smoked cannabis may cause
similar effects to smoking tobacco, with many of them appearing at a
younger age. "
This statement is not only biased, it is incredibly misleading. You
are comparing cigarettes, which you wrote, caused about 120,000 deaths per
year in just Britain alone. Yet no one has ever died from smoking
marijuana. In 4000 years of cultivation and use globally, there is not a
single recorded death that was conclusively attributed to the consumption
of marijuana. However, there is an increased risk for people who have
cardiovascular problems because tetrahydracannabinol-9 increases the heart
rate considerably, as it is a stimulant. If someone is also on
prescription drugs that happen to increase the heart rate, the person
would be at risk as well because of the over-stimulation. In such cases a
person at risk should avoid usage, but the use of marijuana cannot be a
direct causal link to their death because that person already had a
condition which made their cardiovascular system unstable.
By the same token of your argument, someone with persistent arythmia
could die from drinking too much coffee but that doesn't mean we should
ban caffeinated beverages. The few sudden deaths that have ever occurred
after cannabis ingestion were caused either by an allergic reaction to the
THC (which is very rare but possible) or a predisposition to cardiac
abnormalities.
Competing interests: Excessive bias, lack of research, numerous discrepancies