Marijuana users may think they’re perfectly capable of handling a car, when in fact their impaired judgement clouds their abilities. Researchers from RTI International have found that stoned people are more likely than those who are sober to believe it is safe to drive while under the influence.

"When people are sober, most acknowledge they can't safely drive under the influence of alcohol or marijuana,” said Jane Allen, research analyst at RTI and co-author of the study, in a statement. “The problem is, being intoxicated affects our perceptions of risk."

Allen and her colleagues surveyed 1,352 marijuana users living in Colorado and Washington in 2014. Among these respondents, 865 reported marijuana or hashish use in the past 30 days. Sixteen percent of those users even admitted to being under the influence at the time of the survey.

Respondents who reported being high at the time of the survey were more likely to agree that “it is OK to drive a little bit stoned.” They also said that they might drive high “in certain situations” and wouldn’t get caught doing so.

Allen’s research team hopes its findings can be used to assess whether certain messages are more memorable and persuasive among people who are high. "The public health community would do well to address this in campaign planning and development," she added.

Researchers from the University of Massachusetts Amherst conducted a similar study to examine whether or not college students were against getting in the car with a driver who is under the influence of marijuana. In a survey of marijuana-using students attending the University of Washington and University of Wisconsin, 44 percent of males and 9 percent of females drove under the influence of the drug while roughly half of males and a third of females had ridden with a stoned driver.

“The issue of marijuana-impaired driving is particularly salient for young drivers, for whom the combination of inexperience and substance use elevates crash risk,” said lead researcher Jennifer Whitehill in the statement. “If they are part of a culture that accepts the behavior, their risks increase at a predictable rate that we understand better now.”

The Governors Highway Safety Association recently revealed that while the number of car accidents caused by drunk drivers has declined, car accidents caused by drivers under the influence of marijuana or other drugs has increased. Drivers who tested positive for illegal drugs jumped from 12.4 percent in 2001 to 15.1 percent in between 2013 and 2014 with marijuana being the most common.

Source: Zarkin B, Novak S, Allen J, et al. Association Between Self-Reports of Being High and Perceptions About the Safety of Drugged and Drunk Driving. Health Education Research. 2016.