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Bad Science: Cannabis data comes to the crunch
Bad Science: Cannabis data comes to the crunch
< * w w w .guardian.co.uk/science/2007/jul/28/drugs.drugsandalcohol?
Bad science
Cannabis data comes to the crunch
* Ben Goldacre
* The Guardian
* Saturday July 28 2007
You know when cannabis hits the news you're in for a bit of fun, and this
week's story about cannabis causing psychosis was no exception. The paper
was a systematic review and then a "meta-analysis" of the data which has
already been collected, looking at whether people who smoke cannabis are
subsequently more likely to have symptoms of "psychosis" or diagnoses of
schizophrenia. Meta-analysis is, simply, where you gather together all of
the numbers from all the studies you can find into one big spreadsheet,
and do one big calculation on all of them at once, to get the most
statistically powerful result possible.
Now I don't like to carp, but it's interesting that the Daily Mail got
even these basics wrong, under their headline "Smoking just one cannabis
joint raises danger of mental illness by 40%". Firstly "the researchers,
from four British universities, analysed the results of 35 studies into
cannabis use from around the world. This suggested that trying cannabis
only once was enough to raise the risk of schizophrenia by 41%."
In fact they identified 175 studies which might have been relevant, but on
reading them, it turned out that there were just 11 relevant papers,
describing seven actual datasets. The Mail made this figure up to "35
studies" by including 24 separate papers which the authors also found on
cannabis and depression, although the Mail didn't mention depression at
all.
They also said that "previous studies have shown a clear link between
cannabis use in the teenage years and mental illness in later life". They
then described some of these previous studies. These were the very studies
that are summarised in the new Lancet paper.
But what was left out is as interesting as what was added in. The authors
were clear - as they always are - that there were problems with a
black-and-white interpretation of their data, and that cause and effect
could not be stated simply. For ongoing daily users, as an example, it's
difficult to be clear that cannabis is causing people to have a mental
illness, because their symptoms may simply be due to being high on
cannabis all the time. Perhaps they'd be fine if they were clean.
It was also interesting to see how the risk was numerically reported. The
most dramatic figure is always the "relative risk increase", or rather:
"cannabis doubles the risk of psychosis", "cannabis increases the risk by
40%". Because schizophrenia is comparatively rare, translated this into
real numbers this works out - if the figures in the paper are correct, and
causality is accepted - that about 800 yearly cases of schizophrenia are
attributable to cannabis. This is not belittling the risk, merely
expressing it clearly.
But what's really important, of course, is what you do with this data.
Firstly, you can mispresent it, and scare people. Obviously it feels great
to be so self-righteous, but people will stop taking you seriously. After
all, you're talking to a population of young people who have worked out
that you routinely exaggerate the dangers of drugs, not least of all with
the ridiculous "modern cannabis is 25 times stronger" fabrication so
beloved by the media and politicians.
And craziest of all is the fantasy that reclassifying cannabis will stop
six million people smoking it, and so eradicate those 800 extra cases of
psychosis. If anything, for all drugs, increased prohibition may create
market conditions where more concentrated and dangerous forms are more
commercially viable. We're talking about communities, and markets, with
people in them, after all: not molecules and neuroreceptors.
--
Phil Stovell, Hampshire, UK
< * w w w .guardian.co.uk/science/2007/jul/28/drugs.drugsandalcohol?
Bad science
Cannabis data comes to the crunch
* Ben Goldacre
* The Guardian
* Saturday July 28 2007
You know when cannabis hits the news you're in for a bit of fun, and this
week's story about cannabis causing psychosis was no exception. The paper
was a systematic review and then a "meta-analysis" of the data which has
already been collected, looking at whether people who smoke cannabis are
subsequently more likely to have symptoms of "psychosis" or diagnoses of
schizophrenia. Meta-analysis is, simply, where you gather together all of
the numbers from all the studies you can find into one big spreadsheet,
and do one big calculation on all of them at once, to get the most
statistically powerful result possible.
Now I don't like to carp, but it's interesting that the Daily Mail got
even these basics wrong, under their headline "Smoking just one cannabis
joint raises danger of mental illness by 40%". Firstly "the researchers,
from four British universities, analysed the results of 35 studies into
cannabis use from around the world. This suggested that trying cannabis
only once was enough to raise the risk of schizophrenia by 41%."
In fact they identified 175 studies which might have been relevant, but on
reading them, it turned out that there were just 11 relevant papers,
describing seven actual datasets. The Mail made this figure up to "35
studies" by including 24 separate papers which the authors also found on
cannabis and depression, although the Mail didn't mention depression at
all.
They also said that "previous studies have shown a clear link between
cannabis use in the teenage years and mental illness in later life". They
then described some of these previous studies. These were the very studies
that are summarised in the new Lancet paper.
But what was left out is as interesting as what was added in. The authors
were clear - as they always are - that there were problems with a
black-and-white interpretation of their data, and that cause and effect
could not be stated simply. For ongoing daily users, as an example, it's
difficult to be clear that cannabis is causing people to have a mental
illness, because their symptoms may simply be due to being high on
cannabis all the time. Perhaps they'd be fine if they were clean.
It was also interesting to see how the risk was numerically reported. The
most dramatic figure is always the "relative risk increase", or rather:
"cannabis doubles the risk of psychosis", "cannabis increases the risk by
40%". Because schizophrenia is comparatively rare, translated this into
real numbers this works out - if the figures in the paper are correct, and
causality is accepted - that about 800 yearly cases of schizophrenia are
attributable to cannabis. This is not belittling the risk, merely
expressing it clearly.
But what's really important, of course, is what you do with this data.
Firstly, you can mispresent it, and scare people. Obviously it feels great
to be so self-righteous, but people will stop taking you seriously. After
all, you're talking to a population of young people who have worked out
that you routinely exaggerate the dangers of drugs, not least of all with
the ridiculous "modern cannabis is 25 times stronger" fabrication so
beloved by the media and politicians.
And craziest of all is the fantasy that reclassifying cannabis will stop
six million people smoking it, and so eradicate those 800 extra cases of
psychosis. If anything, for all drugs, increased prohibition may create
market conditions where more concentrated and dangerous forms are more
commercially viable. We're talking about communities, and markets, with
people in them, after all: not molecules and neuroreceptors.
--
Phil Stovell, Hampshire, UK
Re: Bad Science: Cannabis data comes to the crunch
On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
> In fact they identified 175 studies which might have been relevant, but on
> reading them, it turned out that there were just 11 relevant papers,
> describing seven actual datasets.
I hope they haven't been cherrypicking - only selecting the reports that
give the conclusion sought.
--
Phil Stovell, Hampshire, UK
On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
> In fact they identified 175 studies which might have been relevant, but on
> reading them, it turned out that there were just 11 relevant papers,
> describing seven actual datasets.
I hope they haven't been cherrypicking - only selecting the reports that
give the conclusion sought.
--
Phil Stovell, Hampshire, UK
Re: Bad Science: Cannabis data comes to the crunch
Phil Stovell wrote:
> On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
>
>
>>In fact they identified 175 studies which might have been relevant, but on
>>reading them, it turned out that there were just 11 relevant papers,
>>describing seven actual datasets.
>
>
> I hope they haven't been cherrypicking - only selecting the reports that
> give the conclusion sought.
It is far from clear that there was a *causal* connection between
marijuana and psychosis. The authors themselves state:
"The researchers said they couldn't prove that marijuana use itself
increases the risk of psychosis... There could be something else about
marijuana users, 'like their tendency to use other drugs or certain
personality traits, that could be causing the psychoses' "
"The prevalence of schizophrenia is believed to be about five in 1000
people"
So in the worst case scenario that there is a causal connection,
marijuana would increase the risk of schizophrenia from .005 to .007 (7
in 1000 instead of 5 in 1000) or to about .01 to .02 for really heavy
users. In contrast, the risk of developing breast cancer for women is
.14 (28X higher), colorectal cancer about .06 (10X higher), and the
lifetime risk of developing any cancer is about 60X higher.
The main point would be the same: It is an individual's right to decide
whether he or she wants to take the risk of developing some disorder.
Eating a typical Western diet increases the risk of heart disease and
many cancers, but it's still the individual's right to make that choice.
Phil Stovell wrote:
> On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
>
>
>>In fact they identified 175 studies which might have been relevant, but on
>>reading them, it turned out that there were just 11 relevant papers,
>>describing seven actual datasets.
>
>
> I hope they haven't been cherrypicking - only selecting the reports that
> give the conclusion sought.
It is far from clear that there was a *causal* connection between
marijuana and psychosis. The authors themselves state:
"The researchers said they couldn't prove that marijuana use itself
increases the risk of psychosis... There could be something else about
marijuana users, 'like their tendency to use other drugs or certain
personality traits, that could be causing the psychoses' "
"The prevalence of schizophrenia is believed to be about five in 1000
people"
So in the worst case scenario that there is a causal connection,
marijuana would increase the risk of schizophrenia from .005 to .007 (7
in 1000 instead of 5 in 1000) or to about .01 to .02 for really heavy
users. In contrast, the risk of developing breast cancer for women is
.14 (28X higher), colorectal cancer about .06 (10X higher), and the
lifetime risk of developing any cancer is about 60X higher.
The main point would be the same: It is an individual's right to decide
whether he or she wants to take the risk of developing some disorder.
Eating a typical Western diet increases the risk of heart disease and
many cancers, but it's still the individual's right to make that choice.
Re: Bad Science: Cannabis data comes to the crunch
On Jul 30, 2:39 pm, "Dr. Zarkov" <M...@Mongo . com > wrote:
> Phil Stovell wrote:
> > On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
>
> >>In fact they identified 175 studies which might have been relevant, but on
> >>reading them, it turned out that there were just 11 relevant papers,
> >>describing seven actual datasets.
>
> > I hope they haven't been cherrypicking - only selecting the reports that
> > give the conclusion sought.
>
> It is far from clear that there was a *causal* connection between
> marijuana and psychosis. The authors themselves state:
>
> "The researchers said they couldn't prove that marijuana use itself
> increases the risk of psychosis... There could be something else about
> marijuana users, 'like their tendency to use other drugs or certain
> personality traits, that could be causing the psychoses' "
>
> "The prevalence of schizophrenia is believed to be about five in 1000
> people"
>
> So in the worst case scenario that there is a causal connection,
> marijuana would increase the risk of schizophrenia from .005 to .007 (7
> in 1000 instead of 5 in 1000) or to about .01 to .02 for really heavy
> users. In contrast, the risk of developing breast cancer for women is
> .14 (28X higher), colorectal cancer about .06 (10X higher), and the
> lifetime risk of developing any cancer is about 60X higher.
>
> The main point would be the same: It is an individual's right to decide
> whether he or she wants to take the risk of developing some disorder.
> Eating a typical Western diet increases the risk of heart disease and
> many cancers, but it's still the individual's right to make that choice.
Marijuana Psychosis Study, the new "Reefer Madness" scare.
We can very easily be willfully ignorant or willfully opposed to facts
we even know are true. This you well know has been the case with
millions of people in the history of science. For example, dismissing
testimony about a round earth because of popular opinion. An unjust
and unscientific person would have dogmatically stated that the earth
is flat when there was no way to even verify that.
One such assertion was reported as fact as the indisputable results of
a "study" that marijuana use increases the very small risk of
psychosis. The first point is when you look further into the newswire
released by rueters they say the only true statement in the article.
"The researchers said they couldn't prove that marijuana use itself
increases the risk of psychosis". Then we find out that they did not
actually do a "study" at all. Instead the "Selectively" looked at
other studies. Did they look at the Madrid studies or the numerous
studies from the U.S. government that showed marijuana increased brain
cells and fights cancer tumors? NO, I assume not.
Furthermore, The team did not look directly at people who used
marijuana but instead conducted what is called a meta-analysis by
reviewing 35 studies in search of a potential connection between
psychotic illness and using marijuana."
In other words they did not do science, they scoured documents trying
any way they could to dig up a possible connection. Why? Because as
we find out they were not real researcher , but were paid by drug
manufacturers who are lobbying to keep marijuana illegal.
Why do drug manufacturers want marijuana illegal. Because it is a
cancer cure and Alzheimer's treatment, and has thousands of medical
uses and up to 5,000 industrial uses. Including ethanol production, 4
times more efficient than any other plant on the earth. They want
marijuana illegal because legalizing it means lost profit. PERIOD.
It is interesting that this so called "study', by "researchers" paid
by the pharmaceutical lobby, who did no research , but rather dug
through selected research in search of any possible evidence and came
up with nothing but reported it as significant was released right
before a medical marijuana amendment is up for vote in congress. Any
co-incidence?
On Jul 30, 2:39 pm, "Dr. Zarkov" <M...@Mongo . com > wrote:
> Phil Stovell wrote:
> > On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
>
> >>In fact they identified 175 studies which might have been relevant, but on
> >>reading them, it turned out that there were just 11 relevant papers,
> >>describing seven actual datasets.
>
> > I hope they haven't been cherrypicking - only selecting the reports that
> > give the conclusion sought.
>
> It is far from clear that there was a *causal* connection between
> marijuana and psychosis. The authors themselves state:
>
> "The researchers said they couldn't prove that marijuana use itself
> increases the risk of psychosis... There could be something else about
> marijuana users, 'like their tendency to use other drugs or certain
> personality traits, that could be causing the psychoses' "
>
> "The prevalence of schizophrenia is believed to be about five in 1000
> people"
>
> So in the worst case scenario that there is a causal connection,
> marijuana would increase the risk of schizophrenia from .005 to .007 (7
> in 1000 instead of 5 in 1000) or to about .01 to .02 for really heavy
> users. In contrast, the risk of developing breast cancer for women is
> .14 (28X higher), colorectal cancer about .06 (10X higher), and the
> lifetime risk of developing any cancer is about 60X higher.
>
> The main point would be the same: It is an individual's right to decide
> whether he or she wants to take the risk of developing some disorder.
> Eating a typical Western diet increases the risk of heart disease and
> many cancers, but it's still the individual's right to make that choice.
Marijuana Psychosis Study, the new "Reefer Madness" scare.
We can very easily be willfully ignorant or willfully opposed to facts
we even know are true. This you well know has been the case with
millions of people in the history of science. For example, dismissing
testimony about a round earth because of popular opinion. An unjust
and unscientific person would have dogmatically stated that the earth
is flat when there was no way to even verify that.
One such assertion was reported as fact as the indisputable results of
a "study" that marijuana use increases the very small risk of
psychosis. The first point is when you look further into the newswire
released by rueters they say the only true statement in the article.
"The researchers said they couldn't prove that marijuana use itself
increases the risk of psychosis". Then we find out that they did not
actually do a "study" at all. Instead the "Selectively" looked at
other studies. Did they look at the Madrid studies or the numerous
studies from the U.S. government that showed marijuana increased brain
cells and fights cancer tumors? NO, I assume not.
Furthermore, The team did not look directly at people who used
marijuana but instead conducted what is called a meta-analysis by
reviewing 35 studies in search of a potential connection between
psychotic illness and using marijuana."
In other words they did not do science, they scoured documents trying
any way they could to dig up a possible connection. Why? Because as
we find out they were not real researcher , but were paid by drug
manufacturers who are lobbying to keep marijuana illegal.
Why do drug manufacturers want marijuana illegal. Because it is a
cancer cure and Alzheimer's treatment, and has thousands of medical
uses and up to 5,000 industrial uses. Including ethanol production, 4
times more efficient than any other plant on the earth. They want
marijuana illegal because legalizing it means lost profit. PERIOD.
It is interesting that this so called "study', by "researchers" paid
by the pharmaceutical lobby, who did no research , but rather dug
through selected research in search of any possible evidence and came
up with nothing but reported it as significant was released right
before a medical marijuana amendment is up for vote in congress. Any
co-incidence?
Re: Bad Science: Cannabis data comes to the crunch
On Jul 30, 2:39 pm, "Dr. Zarkov" <M...@Mongo . com > wrote:
> Phil Stovell wrote:
> > On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
>
> >>In fact they identified 175 studies which might have been relevant, but on
> >>reading them, it turned out that there were just 11 relevant papers,
> >>describing seven actual datasets.
>
> > I hope they haven't been cherrypicking - only selecting the reports that
> > give the conclusion sought.
>
> It is far from clear that there was a *causal* connection between
> marijuana and psychosis. The authors themselves state:
>
> "The researchers said they couldn't prove that marijuana use itself
> increases the risk of psychosis... There could be something else about
> marijuana users, 'like their tendency to use other drugs or certain
> personality traits, that could be causing the psychoses' "
>
> "The prevalence of schizophrenia is believed to be about five in 1000
> people"
>
> So in the worst case scenario that there is a causal connection,
> marijuana would increase the risk of schizophrenia from .005 to .007 (7
> in 1000 instead of 5 in 1000) or to about .01 to .02 for really heavy
> users. In contrast, the risk of developing breast cancer for women is
> .14 (28X higher), colorectal cancer about .06 (10X higher), and the
> lifetime risk of developing any cancer is about 60X higher.
>
> The main point would be the same: It is an individual's right to decide
> whether he or she wants to take the risk of developing some disorder.
> Eating a typical Western diet increases the risk of heart disease and
> many cancers, but it's still the individual's right to make that choice.
THE SO CALLED STUDY IS STATISTICALLY INVALID AND THEY CAN NOT CLAIM
ANY LINK TO PSYCHOSIS. ALCHOHOL ABUSE DOES HOWEVER HAVE A STRONG
CORRELATION TO PSYCHOSIS.
On Jul 30, 2:39 pm, "Dr. Zarkov" <M...@Mongo . com > wrote:
> Phil Stovell wrote:
> > On Sun, 29 Jul 2007 10:10:54 +0100, Phil Stovell wrote:
>
> >>In fact they identified 175 studies which might have been relevant, but on
> >>reading them, it turned out that there were just 11 relevant papers,
> >>describing seven actual datasets.
>
> > I hope they haven't been cherrypicking - only selecting the reports that
> > give the conclusion sought.
>
> It is far from clear that there was a *causal* connection between
> marijuana and psychosis. The authors themselves state:
>
> "The researchers said they couldn't prove that marijuana use itself
> increases the risk of psychosis... There could be something else about
> marijuana users, 'like their tendency to use other drugs or certain
> personality traits, that could be causing the psychoses' "
>
> "The prevalence of schizophrenia is believed to be about five in 1000
> people"
>
> So in the worst case scenario that there is a causal connection,
> marijuana would increase the risk of schizophrenia from .005 to .007 (7
> in 1000 instead of 5 in 1000) or to about .01 to .02 for really heavy
> users. In contrast, the risk of developing breast cancer for women is
> .14 (28X higher), colorectal cancer about .06 (10X higher), and the
> lifetime risk of developing any cancer is about 60X higher.
>
> The main point would be the same: It is an individual's right to decide
> whether he or she wants to take the risk of developing some disorder.
> Eating a typical Western diet increases the risk of heart disease and
> many cancers, but it's still the individual's right to make that choice.
THE SO CALLED STUDY IS STATISTICALLY INVALID AND THEY CAN NOT CLAIM
ANY LINK TO PSYCHOSIS. ALCHOHOL ABUSE DOES HOWEVER HAVE A STRONG
CORRELATION TO PSYCHOSIS.
