MERCED, Calif.—Parents worried about drug use by their teenage children need look no farther than the medicine cabinet.

A study from the American Journal of Preventative Medicine showed that teens are abusing prescription drugs at a higher rate than ever.

“Teens are getting into the medicine cabinet and helping themselves,” said Dr. Kathleen Cowling, vice president of the American College of Emergency Physicians.

Parents are often oblivious to their children’s misuse of prescription drugs, and, along with the teens themselves, don’t realize the seriousness of using those drugs, Cowling said.

“Prescription drug abuse is second only to marijuana use in teens,” she said.

Access is the primary reason teenagers turn to prescription drugs, Cowling said. A common scenario: A parent undergoes surgery, puts leftover pain pills in a cabinet — and the teen finds those pills.

And once teens get addicted, they can buy the drugs illegally, although Cowling said pills are fairly expensive: One Vicodin tablet fetches $5 to $10 on the street.

According to the Substance Abuse and Mental Health Administration, 15.2 million Americans age 12 and older had taken a prescription pain reliever, tranquilizer, stimulant or sedative for nonmedical purposes at least once in the year before being surveyed.

For teenagers, the numbers are scary: 4.7 percent of 12th graders had abused Oxycontin in 2008, and 9.7 percent had abused Vicodin.

Dr. Najeeb Ansari, a Merced, Calif., pediatrician who has taken care of children for 12 years, said the majority of youngsters under the age of 18 who abuse drugs in Merced County are from a lower socioeconomic group.

“A lot of these kids are seeing drug use in their homes,” Ansari said. “Access to any type of prescription drug would come through their family.”

Ansari said prescription drug use isn’t a major problem in the county. It’s more common to see teens using marijuana.

And it’s not just teenagers who abuse prescription drugs, Ansari said. “College students will use amphetamines or over-the-counter caffeine shots to help them study or get through tests,” he said.

Some of the signs of drug use, according to Ansari, are losing weight, not eating well, sleeping at odd times of the day and losing interest in sports and schoolwork.

Ansari said he talks to teens about drug use when they have an appointment with him, but teenagers don’t see a doctor very often.

“The best approach to drug use is to prevent it,” Ansari said. “The main thing is to be involved in your child’s life. Children need to know someone cares about them.”

A generation after the Rolling Stones sang about “Mother’s little helper,” today it’s her kids who may be popping pills.