After several years of declines, the rate of impaired driving among high-school seniors has leveled off at about 30 percent, according to the National Institute on Drug Abuse (NIDA).

NIDA researchers reported that after falling from 35 percent to 31 percent between 2001 and 2003, the percentage of seniors who said they had driven a car within the past two weeks after drinking heavily or using illicit drugs -- or rode with a driver who had done so -- has remained at about 30 percent through 2006.

Study author Patrick O'Malley noted that 13 percent of seniors reported driving under the influence of marijuana, and 10 percent said they had driven after consuming five or more alcoholic drinks

"These findings are another wake-up call that we cannot afford to be complacent about this great public health risk," said Elias A. Zerhouni, director of the National Institutes of Health. "This study shows that not only are too many teens putting themselves and others at risk by driving under the influence of drugs, but that there has been little improvement in the past six years."

The research was published in the November 2007 issue of the Journal of Studies on Alcohol and Drugs.