Psychosocial factors predict opioid analgesia through endogenous opioid function

Abstract

Use of opioid analgesics for management of chronic nonmalignant pain has become common, yet there are presently no well-validated predictors of optimal opioid analgesic efficacy. We examined whether psychosocial factors (eg, depressive symptoms) predicted changes in spontaneous low back pain after administration of opioid analgesics, and whether endogenous opioid (EO) function mediated these relationships. Participants with chronic low back pain but who were not chronic opioid users (N = 89) underwent assessment of low back pain intensity pre- and post-drug in 3 (counterbalanced) conditions: (1) placebo, (2) intravenous naloxone, and (3) intravenous morphine. Comparison of placebo condition changes in back pain intensity to those under naloxone and morphine provided indexes of EO function and opioid analgesic responses, respectively. Results showed that (1) most psychosocial variables were related significantly and positively to morphine analgesic responses for low back pain, (2) depressive symptoms, trait anxiety, pain catastrophizing, and pain disability were related negatively to EO function, and (3) EO function was related negatively to morphine analgesic responses for low back pain. Bootstrapped mediation analyses showed that links between morphine analgesic responses and depressive symptoms, trait anxiety, pain catastrophizing, and perceived disability were partially mediated by EO function. Results suggest that psychosocial factors predict elevated analgesic responses to opioid-based medications, and may serve as markers to identify individuals who benefit most from opioid therapy. Results also suggest that people with greater depressive symptoms, trait anxiety, pain catastrophizing, and perceived disability may have deficits in EO function, which may predict enhanced response to opioid analgesics.

Conflict of interest statement

The authors report no conflicts of interest.

Figures

Figure 1

Scatterplot of derived blockade effects for MPQ-S ratings of low back pain versus Pain Catastrophizing Scale scores. Blockade effects reflect the difference between placebo condition pre-post drug changes in pain (residualized for baseline pre-drug pain and state negative affect) and the corresponding residualized change in back pain in the naloxone condition.

Figure 2

Scatterplot of derived morphine analgesic effects for MPQ-S ratings of low back pain versus Pain Catastrophizing Scale scores. Morphine analgesic effects reflect the difference between placebo condition pre-post drug changes in pain (residualized for baseline pre-drug pain and state negative affect) and the corresponding residualized change in back pain in the morphine condition..

Figure 3

Mediation pathway between Beck Depression Inventory (BDI) scores and morphine analgesia variable through EO function variable for McGill Pain Questionnaire-Sensory subscale (MPQ-S).

Figure 4

Mediation pathway between Beck Depression Inventory (BDI) scores and morphine analgesia variable through EO function variable for McGill Pain Inventory-Present Pain Intensity (PPI).

Figure 5

Mediation pathway between Trait Anxiety Inventory (TAI) scores and morphine analgesia variable through EO function variable for McGill Pain Questionnaire-Sensory subscale (MPQ-S).

Figure 6

Mediation pathway between Pain Catastrophizing Scale (PCS) scores and morphine analgesia variable through EO function variable for McGill Pain Questionnaire-Sensory subscale (MPQ-S).

Figure 7

Mediation pathway between Pain Catastrophizing Scale (PCS) scores and morphine analgesia variable through EO function variable for McGill Pain Questionnaire-Present Pain Intensity (PPI).

Figure 8

Mediation pathway between Pain Disability Index (PDI) scores and morphine analgesia variable through EO function variable for McGill Pain Questionnaire-Sensory subscale (MPQ-S).