Scientists in the US have made a discovery that helps to explain why people with chronic pain often suffer from anxiety.
Researchers at the University of Vermont (UVM) have found that the body releases the same neurotransmitter, known as PACAP, in response to chronic pain as it does to stress.
It's hoped the discovery could eventually reduce the need for the use of addictive prescription medication, such as opioids, to treat sufferers of both chronic pain and anxiety.
A mice study, published in journal Biological Psychiatry, 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 behaviour.
"Chronic pain and anxiety-related disorders frequently go hand-in-hand," said senior author Victor May a professor of neurological sciences at UVM.
"By targeting this regulator and pathway, we have opportunities to block both chronic pain and anxiety disorders," he said.
When May and his colleauges applied a PACAP receptor antagonist - designed to block the release of the neurotransmitter, anxious behavior and pain hypersensitivity were significantly reduced in the mice.
"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 behavioural disorders," said May.
A previous study found that PACAP was highly expressed in women exhibiting symptoms of post-traumatic stress disorder (PTSD).
Anxiety-related behaviours were increased among those who were also suffering from chronic pain.
One in five Australians experience chronic pain and many are treated "inappropriately" with prescription opioids, according to NPS MedicineWise.
When opiods and benzodiazepines - commonly used to treat anxiety disorders - are taken together they can can lead to extreme sleepiness, respiratory depression, coma and even death.
