Federal officials calling it a warning sign said drug use among U. S. adolescents went up between 2008 and 2009.

The results from an annual survey of U. S. teenagers show that previous declines in marijuana, alcohol, and inhalant use have largely leveled off over the past years. Overall declines in drug use have also ticked up since 2007, reversing a trend of less substance use by teens since the late 1990s.

But the researchers who crunch those numbers warned that some of the statistics gleaned from an annual survey of 46,000 Americans in eighth, 10th and 12th graders was worrisome.

"The 2009 Monitoring the Future survey is a warning sign, and the continued erosion in youth attitudes and behavior toward substance abuse should give pause to all parents and policymakers," said Gil Kerlikowske, director of the White House Office of National Drug Control Policy.

Alcohol remains the most common drug used by U. S. adolescents and 43per cent of high school seniors, 29 per cent of 10th graders and 16 per cent of eighth graders reported drinking in the past month.

Nearly one in 10 high school seniors reported taking the narcotic pain killer Vicodin for recreational use, and one in 20 reported using the narcotic OxyContin illegally, the report says.

In a news conference Monday, Kerlikowske called such numbers a warning sign. "When beliefs soften, drug use worsens," Kerlikowske said.