Seniors who smoke weed and drive are road hazards: Study

Many studies have found that getting high on weed and then getting behind the wheel is dangerous for young drivers, and now new research finds it's no different for seniors.

In a driving-simulator experiment, seniors who were long-term marijuana smokers were weaving in and out of their lanes 30 minutes after getting high, Canadian researchers report.

The effect was not seen when the same drivers were tested again three hours after smoking weed. However, the seniors themselves still rated their ability to drive as "impaired."

There was one silver lining: Senior tokers tended to slow their driving speed once high, perhaps because they knew they were intoxicated, said a team led by Patricia Di Ciano, a scientist at the Center for Addiction and Mental Health in Toronto.

Di Ciano's team noted that the percentage of aging Boomers who regularly use marijuana continues to rise.

They believe that "older adults may be particularly affected by cannabis, given age-related changes in cognition," they added. Many seniors are also prescribed medications, and the combination of those meds with marijuana could also be problematic.

While there's been lots of study on the effect of marijuana on younger drivers, the effects of cannabis on driving among seniors "remain unknown," according to the Toronto team.

To help answer the question, they recruited 31 seniors, averaging about 69 years of age, to sit in a special virtual driving simulator.

All participants were longtime, frequent weed users (40 years, on average), and all were told to come to the experiments with their preferred type of legal marijuana. They were told to smoke the marijuana at their "usual amount."

Each participant's driving skills were then tested in the simulator at two time points: 30 minutes after getting high and then again at 180 minutes.

Significant evidence of "weaving" appeared at the 30-minute mark, although drivers also tended to slow down at this point, the researchers noted.

This wandering in and out of lanes appeared to disappear by the 180-minute mark, Di Ciano's group said.

However, when queried, participants "still rated their ability to drive at 180 minutes as impaired," according to the study.

Blood samples were taken during the experiments, and "THC levels were above the legal threshold [for driving] for most participants," Di Ciano's group noted.

There's a theory that people who've regularly smoked marijuana for decades might build up a "tolerance," so perhaps their driving skills wouldn't be affected.

The new study proved that theory false.

Based on the findings, "cannabis can impair driving in older adults when they smoke their usual product," Di Ciano and her team concluded.

Their advice: "Older drivers should refrain from using cannabis when contemplating operation of a motor vehicle."

The study was published in the Jan. 18 issue of JAMA Network Open.

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