Cannabis users should wait at least five hours after smoking a joint before attempting to drive a car, according to a new study into the duration of impairment caused by the drug.
Presenting their findings in the journal Neuroscience and Behavioral Reviews, the researchers sought to provide evidence that could assist the authorities in devising laws regarding driving after cannabis use.
Analyzing the recorded data, they found that tetrahydrocannabinol – the main psychoactive component of cannabis – impairs a number of aspects of driving, including reaction time and the ability to remain in the center of a lane.
However, the majority of these skills tend to recover around three hours after smoking a moderate amount of THC, which the study authors define as 10 milligrams, with driving ability virtually back to regular levels after five hours.
Yet the study authors concede that “there appears to be no universal answer to the question of ‘how long to wait before driving?'”, as a number of factors appear to influence the amount of time it can take for the effects of cannabis to wear off.
“Our analysis indicates that impairment may last up to 10 hours if high doses of THC are consumed orally,” explained study author Dr Danielle McCartney in a statement.