Pain is not a response that's simply caused by a physical lesion alone; it's a complex phenomenon with massive psychosocial and neurochemical contributors as well. And just like how poor sleep can (indirectly) cause an increased sensitivity to pain, perhaps mental distress can as well.
We all know negative stress as causing potentially negative effects on the body. Many of you may also have heard of cortisol, the stress hormone. Or, to get technical, the hormone released by your body in response to stress to take part in the fight-or-flight response, regardless of how major or minor.
Cortisol also has this interesting effect on pain, with several demonstrations showing a decreased pain threshold and increased sensitivity while subjects were under mental strain.
This can have huge implications from a rehab perspective, especially in chronic pain cases. Even as tissue heals and rehab programs are followed, negative stress can certainly interfere in the regression of pain symptoms. This is largely why conditions such as fibromyalgia are commonly looked into, at least in part, as a stress disorder.
This could be particularly problematic with progressive pain and stress before intervention occurs. As we are finding, chronic pain clients typically have an elevated cortisol level even when looking at them in absence of stress-specific factors. This implies that the body may be pumping out even more stress hormones simply in response to pain (as seems reasonable), resulting in a potential cycle of pain and cortisol continually causing one another to spike.
Fortunately, this opens up more avenues of treatment as well. Simply doing mental relaxation exercises and activities is showing positive effects on many chronic pain conditions. This goes to show the importance of stress management when it comes to long-term or complicated pain cases. We often overlook this mental side of physical pain, but disregarding it means overlooking a crucial avenue for recovery.