About 25 percent of young Americans will abuse prescription pain drugs in their life time. For some, that will lead to street drugs, including heroin. A new study sheds light on that connection.

Researchers from Drexel University's school of public health questioned 18- to 25-year-old drug abusers about their drug history. Many said they started out with prescription pain medication in their early teens, and then moved on to heroin.

Drexel University's Stephen Lankenau, lead investigator for the study, cautioned that only a small portion of those who abuse prescription pain medications go on to become heroin users. He said, however, that most of the heroin users who were interviewed for the study started out with pain medications.

Many received pain killers from their doctors for legitimate reasons, a broken bone or wisdom teeth, or got the pills from relatives and friends. Lankenau said the link suggests that doctors prescribing these medications have to keep a close watch on their young patients, to make sure they are not abusing them or passing them on to friends.

Lankenau said doctors prescribing pain medicine or stimulants such as Ritalin should get a better sense of their young patients.

Doctors should be "delving deeper into their own history, family history, involving the parents in the discussion," said Lankenau.

In that way, they can "ensure that there is nothing out of the ordinary in terms of the young adult's behavior at home, school, interactions with friends, family," said Lankenau, who is working on a larger-scale study on the same subject.