Teen drug use continues its overall decline, but that progress does not extend to powerful prescription painkillers, such as OxyContin and Vicodin, a new national study shows.

The report found the highly addictive narcotic painkillers that imitate morphine remain as popular as ever among the nearly 50,000 teens surveyed. Painkiller abuse is second only to marijuana use, according to the survey by the University of Michigan's Institute for Social Research, funded by the National Institute on Drug Abuse.

Drugs with some of the steepest declines in use over the past five years are marijuana, Ritalin and methamphetamine. In 1999, the year the survey began tracking meth use, 4.7 percent of high school seniors said they had used the stimulant in the past year. This year, 1.7 percent reported doing so.

Such declines have driven overall usage data down significantly from its peak years in the late 1990s. In 1997, 42.4 percent of high school seniors reported using some type of illicit drug in the previous year, compared with 35.9 percent this year.

Eighth-graders showed the sharpest decline in reporting past-year drug use, decreasing from 14.8 percent in 2006 to 13.2 percent this year.

Meanwhile, the number of teens who reported using OxyContin in the past year has increased 30 percent since 2002, when survey researchers first asked about the drug. OxyContin use this year ticked up slightly among high school seniors to 5.2 percent, from 4.3 percent in 2006.

One out of 10 high school seniors reported using Vicodin in the past year, a rate that has not changed significantly since the 2002 survey.

Marijuana remains the most widely used drug. One in 10 eighth-graders, one in four 10th-graders and nearly one in three 12th-graders say they smoked marijuana in the past year. Use among eighth-graders declined from 11.7 percent in 2006 to 10.3 percent in 2007, while use in other grades remained steady.

Use of over-the-counter cough medicine to get high also remained steady at 4 percent of eighth-graders, 5.4 percent of sophomores and 5.8 percent of seniors.

The University of Michigan study, in its 33rd year, surveyed 48,025 students in eighth, 10th and 12th grade in 403 public and private schools.