New research headed by Mark Sullivan at the University of Washington finds that many veterans use opioids over the long term to address chronic pain -- even though the medication doesn't work well if used that way and can lead to addiction.

Researchers tracked the opioid use of one million veterans using recent data from the Veterans Healthcare Administration. They found that more than half continued to use the drugs long term, or at least beyond 90 days.

Pain doctors say that opioids work best in patients who are experiencing acute pain, after surgery or an injury, or to ease patients with terminal cancer.

When used to control chronic pain, the body tends to adjust to the dose, and most patients don't experience significant benefits from taking them long term, according to Michael Ashburn, director of the Pain Medicine Center at the University of Pennsylvania.

Research points to a need for more training, he said.

"Physicians and other health care providers need  have the proper education and training on how to  properly use medications to treat pain, including chronic opioids, how to monitor patients, how to receive these medications, and importantly, know when to stop these medications when they are no longer effective," Ashburn said.

At Philadelphia's VA Medical Center, experts say they have changed how they use opioids -- and try to take a comprehensive approach to pain management.

In many cases, that means adjusting expectations, said Nancy Wiedemer, pain management coordinator at the medical center.

"Helping an individual to know that we're going to help them improve function, and quality of life, but maybe not take all of their pain away, is a very difficult concept for individuals to understand," she said.

The Philadelphia VA hospital offers a seven-week course on pain management, and comprehensive care includes yoga and cognitive behavioral therapy.