A new study of U.S. military veterans has shown that those who abuse opioid painkillers are also highly likely to begin using heroin.

Published in the journal Addiction, the study’s authors recommend a close screening of veterans by health care providers for signs of non-medical use of the narcotic painkillers.

The health of almost 3,400 veterans who had never misused painkillers or used heroin was followed for 10 years, for the research. During the course of the study, 500 veterans started using heroin — 386 of these had also begun using prescription painkillers non-medically.

“This study quantifies the issue of starting painkiller misuse and heroin use in a specific, high-risk population — veterans around the U.S.,” said co-author Brandon Marshall of Brown University School of Public Health, in a press release. “Of the 500 participants who initiated heroin, 77 percent reported prior or concurrent non-medical prescription painkiller use.”

While other risk factors for heroin use included being male, being black and abusing stimulant drugs, researchers found that veterans who began misusing painkillers were 5.4 times more likely to use heroin than those who did not.

“Our findings demonstrate a pattern of transitioning from non-medical use of prescription opioids to heroin use that has only been demonstrated in select populations,” said study co-author David Fiellin, a Yale public health and medical professor. “Our findings are unique in that our sample of individuals consisted of patients who were receiving routine medical care for common medical conditions.”

The researchers recommend that even veterans with legal prescriptions should be screened for painkiller abuse, considering the “constellation of risks” they face.

“This paper shows that, as a general clinical practice, particularly for this population which does experience a lot of chronic pain and other risks for substance use including PTSD, screening for non-medical painkiller use, whether you are prescribing an opioid or not, may be effective to prevent even more harmful transitions to heroin or other drugs,” said Marshall.