Study: How Long Does Cannabis Intoxication Last?

A new study from Sydney University aims to find out precisely how much cannabis impacts driving ability.

Unlike alcohol, testing for cannabis intoxication while driving isn't a straightforward process. A roadside saliva test can find if someone has consumed cannabis (typically yielding positive results if cannabis was consumed within 12 hours of testing), but can't tell how intoxicated they are or when they consumed the plant.

This is particularly problematic when one considers the rising use of cannabinoid medicines, and that cannabis patients will likely have to drive within 12 hours of cannabis consumption.

Older studies focusing on driver behaviour under the influence of different intoxicants suggest that weed is less likely to cause problems on the road than other substances like alcohol, however, until now there has been no data that has accurately demonstrated precisely how cannabis consumption can impact driving.

As such, the Lambert Initiative for Cannabinoid Therapeutics, based out of Sydney University, has been conducting research into THC impairment in humans.

Having analysed 80 scientific studies on the subject, the new results are encouraging in that they reveal a more exact spectrum of intoxication. The hope now is that any incapacitation will be more easily gauged at roadside tests and DUI laws can be applied in more relevant ways for patients.

Breaking it down, the results show that those having taken moderate to high levels of THC are likely to be impaired between 3 and 10 hours. when compared to having taken high levels of alcohol, is on a par or indeed points to fewer hours needed to recover in order to complete complex tasks.

The study shows that the frequency and method of THC ingestion will affect the level of impairment, with high-dose THC edibles being more likely to incapacitate individuals for longer periods.

Interestingly, on average, results also showed that regular cannabis users were less likely to be incapacitated by the THC, however, the Lambert Initiative stresses that this is not an excuse to drive under the influence. They concluded that people should wait for at least 6 or 7 hours after inhaling moderate to high doses before thinking about completing complex tasks like driving.

The hopes are now that these studies will be used to reform current DUI laws in Australia, which are increasingly seen as outdated and ostracising to those with cannabis prescriptions.

Australia's existing roadside saliva tests do not effectively determine whether the subject is actually impaired or not, which raises questions of the test's suitability in our evolving cannabis landscape.

Australian laws state that any THC in your system whilst driving or operating heavy machinery is illegal and punishable with charges of driving under the influence (DUI), which can include fines and loss of license.

The results of the Lambert Initiative studies will hopefully contribute toward more effective roadside testing for weed users that will measure the amount of THC in one's system and therefore, the level of incapacitation (if any) rather than enforcing the blanket ban that currently exists.

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Gabrielle Gross
Gabrielle Gross

Gabrielle is based in Sydney and has an extensive history in broadcast media. An interest in the growth of local cannabis industries has led to her seeking further education and involvement in that sector where possible.