Mindfulness physical therapy, pain management, rehabilitation

Psychological Factors and Endogenous Opioid Function

In a study examining the role of psychological factors in the efficacy of opioid analgesics in the treatment of nonmalignant chronic pain, participants with chronic low back pain who were not chronic opioid users (n=89), completed assessments for negative affect, anger, depression, anxiety, positive affect, pain catastrophizing and perceived disability.1 Subjects participated in three identical sessions, scheduled 1 week apart, during which pain was assessed before and after receiving 1 of 3 study drugs: a placebo, naloxone or morphine. Endogenous opioid function was indexed by the difference in pain intensity between the placebo and naloxone conditions. Opioid analgesic responsiveness was indexed by the difference in pain intensity between the placebo and morphine conditions.

Results revealed that those with elevated depressive symptoms, trait anxiety, catastrophic thinking and perceived disability were characterized by a deficit in endogenous opioid function. This, in turn, predicted an enhanced responsiveness to opioid analgesic medication. Greater positive affect was associated with comparatively more potent endogenous opioid function and less opioid analgesia.

Burns and colleagues concluded that patients with high levels of negative psychological factors may experience greater benefit from opioid medications than those with a more positive psychological profile. Unfortunately, these same patients may be at increased risk of opioid misuse.2 Given that opioid analgesics may work best for the patients most at risk of misuse, researchers suggest nonpharmacological interventions to boost endogenous opioid function, including aerobic exercise and relaxation training, may be important treatment options for these patients.

1Burns JW, Bruehl S, France CR, et al. Psychological factors predict opioid analgesia through endogenous opioid function. Pain. 2017;158(3):391-399.
2Arteta A, Cobos B, Hu Y, et al. Evaluation of how depression and anxiety mediate the relationship between pain catastrophizing and prescription opioid misuse in a chronic pain population. Pain Med. 2016;17(2):295-303.