Underage male college students who admitted to smoking marijuana in the past 28 days tended to drive under the influence of the substance.

The rates of these individuals driving under the influence of marijuana was double what it was for drunk driving, a University of Massachusetts at Amherst news release reported.

"[Forty-four] percent of males and [nine] percent of females drove after using the drug, and 51 percent of males and 35 percent of females rode as a passenger with a marijuana-using driver," the news release reported.

Many people believe driving under the influence of marijuana is safe.

"There seems to be a misconception that marijuana use is totally safe, but as an injury prevention researcher I dispute that. We've done a good job in public health with messages about the risks of driving after alcohol use. Clearly the idea not to drink and drive has come through for these students, because we found only [seven] percent engage in that behavior. But our study suggests we must do better when it comes to marijuana, since we found that 31 percent of marijuana-using students drive under its influence," Lead author Jennifer Whitehill at UMass Amherst said in the news release.

"What I feel is, let's create a culture where we don't engage in any of these risk enhancing behaviors before we get behind the wheel," she said.

Marijuana is currently decriminalized in 16 states, raising concerns about drug-impaired drivers.

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

In the study 30 percent of male and 13 percent of female participant admitted to using within the previous 28 days.

"Our findings are consistent with common knowledge and anecdotes indicating that students drive after using marijuana. And it wasn't surprising to find that more men in particular drive after using marijuana compared to women. But our study quantifies the prevalence, which is useful in setting priorities for public health action. We also quantified the likelihood that someone will ride as a passenger with a driver who has used marijuana, and how much it rises with the proportion of their friends who use marijuana," Whitehill said.

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