Pubdate: Thu, 03 Nov 2016
Source: Province, The (CN BC)
Copyright: 2016 Postmedia Network Inc.
Authors: Stephanie Lake and M-J Milloy
Page: 14


Re: Fatal car crashes triple among drivers high on marijuana after 
legalization in Colorado; double in Washington state, Oct. 30

Before raising the alarm on cannabis-impaired motor vehicle accidents,
the stats presented in this article require additional clarification
and contextualization.

Unlike alcohol, for which there is a close correlation between
blood-alcohol content and impairment, there is no defined standard of
impairment for cannabis.

Determining whether or not these drivers were impaired by cannabis is
further complicated by the fact tetrahydrocannabinol (THC) - the
primary psychoactive component in cannabis - can be detected in the
blood several days or even weeks after consuming cannabis.

This means the observed increases in the proportion of fatally injured
drivers testing positive for cannabis in these states might not
indicate increases in cannabis-impaired driving, but rather general
increases in cannabis use following legalization.

This is particularly plausible when we take into consideration the
overall rate of motor vehicle accidents over time. Surveillance for
cannabis among drivers in Colorado and Washington likely increased
with legalization.

While close monitoring of cannabis and driving will be a top public
health priority following legalization in Canada, it is important we
carefully consider the context and limitations of this type of data.

Stephanie Lake and M-J Milloy, Urban Health Research Initiative, B.C.
Centre for Excellence in HIV/AIDS
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MAP posted-by: Matt