By Pat Anson, Editor

A new study helps explain why so many chronic pain patients also suffer from anxiety or depression.

Researchers at the University of Vermont discovered that the body releases the same neurotransmitter in response to stress as it does to chronic neuropathic pain. The findings, published in the journal Biological Psychiatry, could lead to the development of a new and safer class of medication that could treat both pain and anxiety.

In studies on laboratory mice, researchers found that pain signals and the PACAP neurotransmitter (pituitary adenylate cyclase activating polypeptide) share the same pathway to the brain - the spino-parabrachiomygdaloid tract - which travels from the spinal cord to the amygdala, where the brain processes emotional behavior.

"Chronic pain and anxiety-related disorders frequently go hand-in-hand," says senior author Victor May, PhD, a professor of neurological sciences at the University of Vermont. "By targeting this regulator and pathway, we have opportunities to block both chronic pain and anxiety disorders."

May and his colleagues found that anxious behavior and pain hypersensitivity were significantly reduced when a PACAP receptor antagonist -- designed to block the release of the neurotransmitter -- was applied.

"This would be a completely different approach to using benzodiazepine and opioids - it's another tool in the arsenal to battle chronic pain and stress-related behavioral disorders," said May, who found in a previous study that PACAP was highly expressed in women exhibiting symptoms of post-traumatic stress disorder (PTSD).

May’s findings are important because anxiety and stress are currently treated with sedatives, benzodiazepines and other central nervous system (CNS) depressants. When taken with opioid pain medication, the combination of the drugs can lead to extreme sleepiness, respiratory depression, coma and death.

Yesterday, the U.S. Food and Drug Administration ordered new “black box” warning labels be put on all medications that contain opioids, benzodiazepines and CNS depressants, warning patients and physicians about the increased risk.

According to a 2015 study, over a third of the patients prescribed opioids for chronic musculoskeletal pain were given a sedative. And patients with a history of psychiatric and substance abuse disorders were even more likely to be co-prescribed opioids and sedatives.