Adults with mental health disorders are consuming more than half of all painkillers prescribed in the United States, according to a new study.

While adults suffering from depression, anxiety and mood disorders represent just 16 percent of the nation's population, they received 51 percent of all opioid prescriptions.

Researchers at the University of Michigan and Dartmouth-Hitchcock Medical Center said that rethinking pain management among this group is "critical" to combat a growing national opioid addiction epidemic — one that has hit Tennessee particularly hard.

Tennessee leads the nation in the number of opioid prescriptions per person and has a five-year overdose death toll that has climbed to 6,036 people.

"When we got the results, we were completely shocked at the large discrepancy in prescribing," said Dr. Brian Sites, an anesthesiologist at the Dartmouth-Hitchcock Medical Center and a co-author of the study published in the Journal of the American Board of Family Medicine.

"The sheer magnitude suggests the possibility of over-prescribing," Sites said. "There's just no way all these prescriptions are needed."

But the leader of Tennessee's Department of Mental Health and Substance Abuse Services cautioned against drawing sweeping conclusions or tailoring public policies around the conclusions of one study.

"If the study bears out with further research, our department will be the first to say we want to develop ways in which we can serve that population," said Marie Williams, the department's commissioner.

"If it doesn't, we don't want to further stigmatize a group that is already stigmatized."

Opioids were the number one substance abused in 2016 by individuals with mental illness who were receiving services from the Department of Mental Health and Substance Abuse Services, with alcohol a close second.

Opioid crisis 'knows no bounds,' says Health and Human Services Secretary Tom Price

Williams noted the study did not focus on individuals known to be abusing opioids. The study defined opioid users as anyone who had two or more prescriptions per year. It also did not include people living in institutions such as mental health facilities or jails.

Addiction treatment experts say they have long seen a correlation between mental health disorders and substance abuse, but the study is a first to put a number on those cases.

"The large number using opioids — that's more than would have been anticipated," said Dr. Karen Rhea, chief medical officer for Centerstone, which treats more than 65,000 people in Tennessee at its behavioral health centers.

Rhea said chronic physical pain among people with depression and anxiety is a real problem, not a phantom one, she said.

An internal analysis of Centerstone patient data found that chronic pain was a risk factor for attempted or completed suicide, Rhea said.

The cause and effect may differ among individuals, she said. People with back pain or those who suffered debilitating injuries may be at risk for depression, while individuals who suffer anxiety can experience so-called somatic disorders, which are symptoms of physical pain exacerbated by intense anxiety about that pain.

Sites, the study researcher, said while more research is needed, one key to solving it is clear.

"This isn't a drug cartel problem," he said. "This is a physician prescribing problem. We know where it starts."

The majority of physicians would agree with the study's conclusion that improving pain management is critical to reducing opioid dependency among all populations, said Nita Shumaker, a Chattanooga pediatrician and president of the Tennessee Medical Association said

But Shumaker said physicians need more tools to help patients with chronic pain and those at risk for addiction.

Although mandatory training is now required for medical professionals who prescribe opioids, Shumaker said the group would be working in the coming year to provide education to both doctors and their patients to help them manage "complex medical conditions while managing pain with alternative treatment models."

Meanwhile, there are efforts underway in Tennessee aimed specifically at people with "dual diagnoses" — those with mental health illness and addiction.

Centerstone in February launched an anxiety recovery program aimed at educating patients with chronic anxiety about how it interacts with physical pain, Rhea said.

And the Department of Mental Health and Substance Abuse Services has launched an initiative with the Tennessee Hospital Association to create a protocol for emergency rooms that identify people with anxiety or depression and treat them for those conditions, rather than prescribing opioids.

Reach Anita Wadhwani at awadhwani@tennessean.com, 615-259-8092 or on Twitter @AnitaWadhwani.

Need help for addiction or mental health care? Call Tennessee REDLINE: 800-889-9789

Timeline: How the opioids crisis took hold