Cannabis consumers overestimate impairment

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Cannabis consumers overestimate impairment

Re: "Cannabis front and centre in on Parliament Hill"

Kudos to NDP MP Alistair MacGregor for pressuring the federal government to desist from criminalizing cannabis consumers while we wait for their new regulatory regime.

MacGregor cautioned, "We do not yet know how much cannabis needs to be in the body for a person to be too impaired to drive, and we are unsure if the devices that test cannabis levels can work in cold temperatures."

We will never know how much cannabis needs to be in the body for a person to be too impaired to drive because the amount varies depending on experience and tolerance.

We also lack a roadside screening device and legally established blood concentrations for a medicine cabinet full of impairing OTC medications and pharmaceuticals, including marinol (dronabinol), the legal, synthetic THC pill.

Cannabis usage rates rise and fall with no statistical relationship to cannabis laws and their enforcement, so there is no reason to presume more motorists will be impaired by cannabis post legalization, however cannabis is an economic substitute for alcohol and other more impairing substances, such that when cannabis use goes up, drinking and impaired driving go down.

An average dose of cannabis impairs an average cannabis consumer less than a glass of wine, less than a .08 BAC. The label on marinol warns patients not to drive until they are accustomed to the drug. Happily, cannabis and marinol consumers tend to overestimate their impairment and either refrain from driving or drive more defensively to compensate. The exact opposite is true of alcohol. Drinkers tend to underestimate their impairment and drive more aggressively.

Matthew M. Elrod


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