Pubdate: Thu, 14 Aug 2014
Source: Boulder Weekly (CO)
Copyright: 2014 Boulder Weekly
Contact:  http://www.boulderweekly.com/
Details: http://www.mapinc.org/media/57
Author: Leland Rucker

CRUNCHING NUMBERS IN THE CANNABIS DEBATE

When it comes to statistics, both sides of the cannabis issue have
plenty to show off.

"Thirty-six percent of high-school seniors have used cannabis in the
past year, and an alarming 6.5 percent smoked cannabis daily, up from
2.4 percent in 1993," states a report released in April by Springer
International Publishing. Yet, "30-day marijuana use fell from 22
percent in 2011 to 20 percent in 2013, and lifetime use declined from
39 percent to 37 percent during the same two years," are among the
findings just released from the Colorado Public Health and
Environment's 2013 Healthy Kids Colorado Survey.

A Rocky Mountain High Intensity Drug Trafficking Area report says:
"From 2006 to 2011, traffic fatalities decreased in Colorado 16
percent, but fatalities involving drivers testing positive for
marijuana increased 114 percent." But a Washington Post study of
traffic in Colorado since legalization shows that traffic fatalities
in Colorado in 2014 are down from last year.

WTF? Who to believe? The cannabis debate is being waged in a blur of
disparate numbers. It appears, at least from state reports and a few
outside ones, for instance, that legalization in Colorado and
Washington and the medical cannabis allowed in 35 other states seem to
be proceeding fairly smoothly, yet if you listen to Patrick Kennedy or
Kevin Sabet, the mouthpieces for national prohibitionist group SAM
(Smart Approaches to Marijuana), you'd think an impending zombie
apotcalypse [sic] is being unleashed upon us.

When it comes to statistics, I come from the old school. I generally
don't trust them and follow the precepts outlined by C. Davenport
Hughes in The Incorporated Statistician in March 1964. The dangers of
statistics, he wrote, include: 1) Too much hurry to know too many
things 2) Having to deal with too much data whose nature and quality
are too little known 3) Too great an insistence on positive,
unreserved conclusions 4) Too naive a belief in the ability of
statisticians to prophecy 5) Too much confidence in purely
mathematical processes 6) Coming to think of data only in terms of
numbers and thus seem more valid or significant than they sometimes
are.

All of these, I think, are in play today in the cannabis debate. We
won't really have any real numbers or serious analyses of how
legalization will play out for at least a couple of years, but that
hasn't stopped both sides from promoting whatever numbers and stats
help prove their point. Data and studies on cannabis are voluminous -
type "marijuana" into PubMed.com for a more-than-generous sample - and
there are enough contradictions that either side can draw "unreserved"
conclusions from the same data set.

News media unwittingly play into the statistics game. We need look no
farther than April, when news stories began to circulate in seemingly
every newspaper and website about a study published in The Journal of
Neuroscience under the general headline, "Even casual marijuana use
can cause abnormalities in the brain."

The researchers took one MRI scan of the brains of 40 Boston-area
college students, 20 of whom reported being occasional users and 20
who said they weren't, and found that that certain parts of the brains
of those who used cannabis were shaped differently than those who weren't.

"People think a little recreational use shouldn't cause a problem, if
someone is doing OK with work or school," lead researcher Hans
Breiter, who led the new study, told USA Today. "Our data directly say
this is not the case."

The first thing that struck me was that a study that looked at only 40
people who reported being users or non-users is using a mighty small
sample to reach a major conclusion. It breaks almost every one of the
Hughes danger signs, especially the one that warns of thinking of data
only in terms of numbers and thus seeming more valid or significant
than they sometimes are.

As it turns out, others with much more medical experience than me also
have questioned Breiter's methodologies and conclusions. Lior Pachter,
in a weblog post titled "Does researching casual marijuana use cause
brain abnormalities?," finds serious issues with the study's sample
size, definition of "recreational user" and the extent of testing.
Most seriously, he finds that "correlation does not imply causation,"
and that the research doesn't match the conclusions.

But check a search engine and you'll see mostly pages and pages of
headlines that parrot Breiter's findings and state that occasional use
of cannabis can cause brain abnormalities. And already, like another
controversial study (which suffers from similar methodology problems)
that suggests that cannabis use by young people can cause permanent IQ
loss as they get older, the "abnormal brain" meme is now prominent on
prohibition websites as another example of the multiplicity of
problems associated with cannabis.

I can't say it enough. When it comes to cannabis, be careful what you
read.

You can hear Leland discuss his most recent column and Colorado
cannabis issues each Thursday morning on KGNU.

http://news.kgnu.org/category/features/weed-between-the-lines/
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MAP posted-by: Matt