According to a new study, marijuana use among teens is currently at its highest level in 30 years and 19 percent of teen drivers reported driving under the influence of marijuana. What's more, 36 percent of the teens surveyed said they are confident the drug has no effect on their abilities behind the wheel.

The study, conducted by Students Against Destructive Decisions (SADD) and Liberty Mutual Insurance, also revealed that 19 percent of adolescents don't believe alcohol has a negative effect on driving.

Overall, teens are more likely to bring up safety issues with friends who've been drinking alcohol than those smoking marijuana, according to the report.

The study also revealed that females are more likely than males to ask a friend to refrain from driving after drinking or using marijuana.

On the other hand, 94 percent of drivers who've been drinking and 90 percent of drivers who've been smoking said they would hand over the keys if their passengers requested they do so.

Stephen Wallace, SADD's senior adviser for policy, research and education, told USA Today that the study highlights some disturbing perceptions.

"We hear from young people who believe that marijuana actually makes them a safer driver, that they concentrate harder, drive slower," Wallace told the paper. But "marijuana affects memory, judgment, and perception."

A recent study published in the British Medical Journal suggests that people who drive within three hours of using marijuana are twice as likely to get into an accident than those who are sober, the Atlantic highlights. The risk also increased among people younger than 35.

On the other hand, results of a 2010 study suggests precisely the opposite.

A double-blind, placebo-controlled trial conducted by Connecticut's Hartford Hospital and the University of Iowa revealed that people who smoked marijuana 30 minutes before getting behind the wheel did not react much differently than they had before being given the drug.

Regardless of the conflicting data and possible causes, the number of fatal car accidents involving teens increased during the first half of 2011, the Washington Post observed.

The data, released by the Governors Highway Safety Association on Feb. 16, show that while the number of total deadly accidents has decreased, the number has risen among 16 and 17-year-old drivers.

Although SADD's study suggests marijuana use is at a 30-year high among teens, the Hartford Courant points out that government surveys through 2009 have indicated a decline in marijuana use among adolescents.