Frequent pot smokers are dangerous drivers when sober study suggests

Frequent marijuana use can affect someone’s driving ability long after the "high" dissipates, a new study suggests.

In a study published in the Drug and Alcohol Dependence journal, researchers at McLean Hospital found that heavy, recreational marijuana users were worse drivers even when sober, compared to non-users.

“People who use cannabis don’t necessarily assume that they may drive differently, even when they’re not high,” said Staci Gruber, senior author of the study. “We’re not suggesting that everyone who uses cannabis will demonstrate impaired driving, but it’s interesting that in a sample of non-intoxicated participants, there are still differences in those who use cannabis relative to those who don’t.”

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After conducting a driving simulation, researchers found that users, specifically those who started using before the age of 16, had more accidents, drove at higher speeds, and drove through more red lights than non-users.

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However, as legal recreational cannabis use expands across the United States, so has public concern about the drug's effect on activities, like driving, that present safety issues. To date, cannabis is the most widely cultivated, trafficked and abused illicit drug, according to the World Health Organization.

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For the purpose of the study, researchers compared 28 cannabis users against 17 non-users from the Greater Boston Metropolitan area. Heavy users were defined as those who smoked at least five of the last seven days, reported at least 1500 lifetime uses, and tested positive for urinary cannabinoids, the study said.

At the time of the experiment, the marijuana users had not smoked pot for at least 12 hours and were not intoxicated. Overall, researchers found that the "bad driving" was localized to those who began using the substance regularly before age 16.

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Coincidently, the results of study came just ahead of the 100th anniversary that America went dry — at least for 13 years.

America’s happy hour was officially threatened on Jan. 16, 1919, when Congress ratified the 18th Amendment, instituting a ban, which prohibited the creation, transportation and sale of alcohol in the country, which was known as Prohibition. It went into effect on January 17, 1920 — 100 years ago, this Friday.

The Associated Press contributed to this report. 

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