Saturday, February 9, 2008

Latest Anti-Pot Quack Science: 'Marijuana Makes Your

Teeth Fall Out'

By Bruce Mirken, AlterNet

Posted on February 9, 2008, Printed on February 9,



Recent weeks have seen a rash of new studies of

marijuana hitting the mass media, generating scary

headlines like "Smoking Pot Rots Your Gums," "Cannabis

Bigger Cancer Risk Than Cigarettes," and "Pot

Withdrawal Similar to Quitting Cigarettes. Most of

this coverage can be boiled down to a fairly simple



Flawed science + uncritical reporting =



Mercifully, the U.S. mass media were so distracted by

Super Tuesday, Heath Ledger's autopsy and the latest

Britney Spears trauma that reports of these studies

didn't get as much play as they might have. That's

good, because the research had significant gaps, and

the reporting ranged from slapdash to flat wretched.




The lung cancer study was the scariest. Since

cigarettes are a known lung cancer risk, it seems

plausible that marijuana might carry similar risks. In

fact, most of the scientific evidence tends in the

opposite direction -- though one would never know it

from reading either the study or the Reuters wire

story that got the heaviest circulation.


Conducted in New Zealand, this was what is called a

"case-control" study, in which researchers looked at a

group of patients who had lung cancer and compared

them to a group without cancer -- the controls --

matched for age and other demographics. All were asked

about various factors that might increase their lung

cancer risk, including smoking cigarettes or

marijuana. After running the data on 79 cancer cases

and 324 controls through myriad equations and

mathematical analyses, the researchers proclaimed that

one joint packed a cancer risk roughly equal to 20

cigarettes -- an assertion that became Reuters' lead.


What was downplayed in the study, published in the

European Respiratory Journal, and missing entirely

from most media reports was context -- context that

strongly suggests that its alarming conclusion is



For one thing, the new conflicts with other, much

larger studies. In a study published in 1997,

Kaiser-Permanente researchers followed 65,000 patients

for 10 years and saw no sign of marijuana use

increasing the risk of lung cancer or other

smoking-related cancers. And a UCLA study similar in

design to this one, published in 2006, found a trend

toward lower lung cancer rates among marijuana

smokers. Instead of 79 cancer cases, the UCLA team

looked at 1,212. The result was so striking that they

speculated that it "may reflect a protective effect of



That's right: Marijuana might protect from cancer.

Piles of published studies going back to the mid-1970s

document the cancer-fighting properties of marijuana's

active components, THC and other chemicals called

cannabinoids. Anticancer activity has been shown in

many types of malignant cells, including lung cancer

cells. So even though marijuana smoke contains tars

and other potentially carcinogenic compounds, it is

entirely plausible that cannabinoids counter any

harmful effects.


But even without such context, a closer look at the

New Zealand data raises questions that should have

been asked by reporters. For example, most marijuana

smokers in the study actually didn't show an increased

risk of cancer. The only group that did was those

whose marijuana use equaled at least 10.5

"joint-years" (one joint-year equals smoking a joint

every day for one year). That group constituted a

whopping 14 people. All those complicated mathematical

models leading to the "20 times the risk" assertion,

and contradicting reams of published research, rest on

exactly 14 people.




The gum disease study was even more tenuous, but again

you would never know it from most of the coverage.

Researchers -- also in New Zealand -- followed 903

participants from birth through age 32. At ages 18,

21, 26, and 32, they were asked whether they had used

marijuana in the past year, and how often. The

heaviest marijuana users had a 60 percent increased

risk for gum disease after controlling for several

factors that might affect their risk, including

cigarette use and professional dental care.


The researchers were careful to say they hadn't proved

cause-and-effect, but simply what scientists called an

"association." But that didn't stop one U.S. reporter

from writing that marijuana "could ... destroy gum

tissue," and an Australian headline writer from

declaring that marijuana "makes teeth fall out."


Reading the actual study -- something one suspects

most reporters never did -- raises questions the media

never asked. Why is there no indication that

participants were questioned about use of alcohol or

other illicit drugs, both of which are known risk

factors for dental and gum problems? Why were they not

asked about brushing and flossing habits?


Given the relatively small effect -- the statistical

margin of error meant that the increased risk could be

as low as 16 percent -- confounding by alcohol/drug

use or poor dental hygiene could easily explain the

whole difference. In other words, there is a very good

chance this study found nothing real at all.


I raised this issue with an editor at one news

organization, whose story had been particularly

hysterical and lacking in context, asking why they

hadn't noted these potential doubts. The rather snippy

reply: "As for the rest of your concerns, we are

dealing with a peer-reviewed journal study, and I

don't feel at all comfortable going beyond what they

are publishing. That is not our role."


Memo to editors: Journal peer-reviewers are human.

They sometimes miss stuff. When did it stop being a

reporter's job to ask questions?




If you haven't lost your teeth or died of lung cancer

yet, another set of grim headlines warned that

marijuana is as addictive as tobacco -- again, a

conclusion that went beyond the study's findings and

which was almost certainly wrong.


In this U.S. study, researchers took 12 people who

regularly smoked both marijuana and cigarettes and had

them stop using one, the other, and both, in varying

orders. Physiological tests and responses to

questionnaires were used to assess withdrawal symptoms

such as irritability and difficulty sleeping. The

withdrawal symptoms reported were roughly comparable.


But the limitations of this research are obvious. In

fairness, most were acknowledged in the study,

published in the journal Drug and Alcohol Dependence.


For one, the study looked only at regular users of

both substances, so it tells nothing about marijuana

users who do not use tobacco -- a considerable number,

by most accounts. Second, the researchers did not

publish the results for individual participants. In a

sample of 12, one or two extreme responses can skew

the averages enough to make them meaningless.


The researchers also did not note any changes in

participants' use of caffeine or alcohol, which could

easily have affected their findings. Volunteers were

asked not to change their use of these substances, but

we have no clue whether they followed these



And though the overall withdrawal symptom ratings were

similar, ratings of anger and craving were higher for

tobacco than for marijuana. And even in areas where

the two substances were statistically comparable,

there was often a trend toward the tobacco withdrawals

being stronger. Had this been a larger study, those

trends might have reached statistical significance.


Also, the 5-day abstinence period may not have been

enough to fully gauge withdrawal effects. For longtime

cigarette smokers, tobacco cravings can continue for



Finally, a reality check: It is an established fact

that about 32 percent of those who ever touch a

cigarette become dependent on tobacco. For marijuana,

the figure is nine percent. In the real world, it's

clear that marijuana is nowhere near as addictive as

tobacco -- but again, you'd never know it from the

coverage of this study.


In fact, you wouldn't learn much from the coverage of

any of these studies.


Bruce Mirken is communications director for the

Marijuana Policy Project.


© 2008 Independent Media Institute. All rights


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