THURSDAY, Dec. 10, 2015 (HealthDay News) -- Fewer teens and young adults are driving under the influence of alcohol or a combination of alcohol and marijuana, U.S. health officials reported Thursday.
From 2002 to 2014, self-reported driving under the influence of alcohol alone dropped by 59 percent among those aged 16 to 20 and by 38 percent among those aged 21 to 25, the study found.
"The decline in driving under the influence of alcohol is probably due to a combination of factors," said lead researcher Dr. Alejandro Azofeifa, an epidemiologist at the U.S. Substance Abuse and Mental Health Services Administration.
Among these factors are the decline in drinking overall and the decline in binge drinking among high school students, he said.
In addition, underage drinking laws have been more strictly enforced, and graduated driving license laws have required that young drivers don't drink and drive, Azofeifa said.
The researchers also found that driving under the influence of alcohol and marijuana combined declined by 39 percent across both age groups.
However, driving drunk did increase with age, Azofeifa said. Among 16-year-olds, only 1.5 percent drove under the influence of alcohol, but 18 percent of 21-year-olds did, according to the report.
And although there were significant drops in the prevalence of driving under the influence of alcohol and alcohol and marijuana combined, there was little decrease in the number of young adults driving under the influence of marijuana alone, Azofeifa said.
Though driving under the influence of marijuana alone declined 18 percent, from 3.8 percent in 2002 to 3.1 percent in 2014, this drop was seen only among those aged 16 to 20, researchers found.
The reasons why driving under the influence of marijuana alone hasn't declined among other drivers aren't clear, Azofeifa said.
"Driving under the influence of alcohol and marijuana is a risky behavior, and can result in a fatal car accident," he said. "Regardless of the encouraging numbers we are seeing in this report, there are still too many people driving under the influence and too many people dying in car accidents."
Car crashes are the leading cause of death among American teens and young people, he noted.
J.T. Griffin, chief government affairs officer at Mothers Against Drunk Driving, called it "good news that the prevalence of drunk driving is down among young people. It's proof that things like the 21 minimum drinking age are working."
But, he added, "alcohol remains the number one drug that is killing people on the road. There are still too many people dying at every age. We are making good progress, but until we get to a place where there are no more fatalities we still have a lot of work to do."
The study findings appear in the Dec. 11 issue of the Morbidity and Mortality Weekly Report, a publication of the U.S. Centers for Disease Control and Prevention.
For more on drinking and driving, visit Mothers Against Drunk Driving.