Stoned drivers are ‘significantly’ impaired for up to 4 hours after cannabis use: study

Cannabis use can “significantly” impair drivers for up to four hours after use, a new study revealed, stressing the urgency for a better understanding of the effects its use increases aroudn the country.

“Expanding cannabis medicalization and legalization increases the urgency to understand the factors associated with acute driving impairment,” researchers wrote.

The randomized clinical trial of 191 regular cannabis users in the study by University of California, San Diego, the FDA and the Research Advisory Panel of California published last week in the JAMA Psychiatry journal determined that THC consumption “comprised key driving simulator variables, assessed prior to smoking and at multiple time points post-smoking.”

Researchers also measured additional indicators including self-perceptions of driving impairment and cannabis use history.

Gov. Charlie Baker, in his final year in office, is pushing lawmakers to act on legislation filed by his office to toughen up enforcement and penalties for Massachusetts drivers who get behind the wheel when they’re stoned.

His bill is named for State Police Trooper Thomas Clardy, who was killed while conducting a traffic stop on the Mass Pike in Charlton in 2016 when a man with THC in his system crashed his car into Clardy’s cruiser.

A previous version of the bill stalled during the last session.

“Unfortunately, our road safety laws have not caught up to the current public safety landscape with respect to impaired driving,” Baker said when he introduced the bill last November.

But the proposal hasn’t gained support from the Cannabis Control Commission and Democrats have expressed skepticism over the bill’s reliance on so-called “drug recognition experts” — trained police — to detect impairment as study after study has cast doubt on the accuracy of stoned driving tests.

The push to crack down on high driving is likely to continue after Baker leaves office, however, with nearly every candidate agreeing that stricter enforcement is needed.

Frontrunner and current Attorney General Maura Healey said through a spokeswoman “the issue of drugged driving is one that needs careful attention in our impaired driving law” but that any update should “strike the right balance in prioritizing both public safety and civil rights.”

“It’s important to have the tools and technology in place for accurate detection, require transparent data collection, and ensure enforcement without racial bias,” she said.

Danielle Allen, a Harvard professor and Democratic candidate for governor, said while “we absolutely need to prevent impaired driving,” Baker’s bill “is not the way to do it.”

“We don’t yet have accurate tests for whether a driver is cannabis-impaired, so this is an unsafe, unscientific approach that will put people at the mercy of subjective enforcement decisions,” Allen said.

State Sen. Sonia Chang-Diaz, D-Boston, another Democratic contender for governor, declined to comment on Sunday.

Both Republican candidates, however, support Baker’s bill.

Former Whitman state Rep. Geoff Diehl called the bill “long overdue.”

“It will undoubtedly save lives. Police and prosecutors must have the appropriate tools at their disposal to hold people accountable if they endanger the public by operating a vehicle unsafely,” Diehl said in a statement to the Herald.

The newest candidate on the trail, Chris Doughty, also endorsed the bill, saying through a spokeswoman that he’s “in favor of increasing the penalties for driving under the influence of drugs” and having “district attorneys who will prosecute these crimes.”