MARIJUANA CAN IMPAIR DRIVING ABILITY

Neuroscientist Dan Small says there is significant scientific evidence to
refute the belief of Rick Reimer that smoking marijuana doesn't impair
his ability to drive. Mr. Reimer, like Julian Roy, above, is a user of
medicinal marijuana to ease the symptoms of chronic illness.

Re: 'I smoke marijuana constantly': Retired lawyer tackles the law on
driving under influence of drugs, Dec. 12.

As a former resident of Ottawa, I am concerned after reading about Rick
Reimer's intention to argue that smoking marijuana does not impair his
driving ability.

I have sympathy for him having multiple sclerosis, and can appreciate the
desperation he must feel, given that there is no cure yet. As a
neuroscientist, I am working to find effective therapy for multiple
sclerosis.

I do not agree, however, with his argument that marijuana does not
impair him in any way. If smoking marijuana really does improve his
driving, then perhaps his licence should be revoked.

I have not conducted careful studies of the effects of marijuana, or more
precisely THC, marijuana's active ingredient, on cognitive performance
or driving ability, but many competent scientists have.

Although two studies show there is some discrepancy about whether
cognitive performance is adversely affected by acute exposure to THC, a
third study has clearly shown that driving ability is significantly impaired
immediately following cannabis consumption, due to impaired perceptual
motor speed and accuracy.

This finding is consistent with a fourth study in which reaction time was
found to be most sensitive to the effects of marijuana. In a fifth study,
THC impaired visual attention of rodents, another important faculty
required by humans for driving.

The failure to convict the truck driver in the 1997 impaired-driving trial
in Ottawa mentioned in this story is somewhat understandable, given that
these important studies above were only recently published in medical
journals.

I am not opposed to Mr. Reimer's medicinal use of marijuana for
treating his multiple sclerosis, but I hope that in his search for
retribution against the government for having its head in the sand about
the matter of medicinal marijuana, he does not facilitate dangerous
driving conditions.

Dan Small,

The Woodlands, Texas