Buprenorphine may be more effective than opioid therapy in treating symptoms of post-traumatic stress disorder (PTSD) in veterans struggling with chronic pain, PTSD and substance use disorders, a new study suggests.

Researchers found twice as many veterans treated with buprenorphine experienced improvement in PTSD symptoms, beginning at eight months and improving up to 24 months. In contrast, symptoms worsened for veterans treated with opioids, Medscape reports.

The study included 382 veterans of the Iraq and Afghanistan wars who were diagnosed with chronic pain, PTSD and substance use disorders. The researchers found 23.7 percent of veterans in the buprenorphine group experienced significant improvement in PTSD symptoms, compared with 11.7 percent of those treated with moderately high doses of opioids.

“We rarely see patients who have isolated, chronic pain; and, for that matter we rarely see patients who have isolated PTSD or isolated opioid use disorder,” said lead author Karen Seal, MD, MPH of the San Francisco Veterans Affairs Medical Center and the University of California.

“It’s sometimes very hard to get avoidant patients ― and patients who have PTSD are naturally avoidant ― it’s hard to help these patients engage in care. When you have a single medication or a single treatment that can actually address several different components of what they’re suffering from, it’s often easier to get them engaged,” she said.

The study appears in the Journal of Clinical Psychiatry.

According to the researchers, among an estimated half million U.S. veterans who served in Iraq and Afghanistan and who received a diagnosis of chronic pain, those with PTSD were much more likely to receive opioid prescriptions, to misuse these medications, and to have a higher risk for overdose, injuries and suicides.