Human Studies

Children who develop greater negatively biased recall of pain (i.e., recalled pain is higher than the initial pain report) following surgery are at risk for developing chronic pain; therefore, identifying risk factors for the development of biased pain memories is important. Higher anxiety has been implicated in the development of greater negatively biased recall of pain; however, studies have not examined anxiety at multiple time points before and after a surgery and its relationship to children's post-surgical pain memories after one year. This prospective study examined a cohort of 237 children and adolescents undergoing major surgery. Anxiety sensitivity, pain catastrophizing, and pain anxiety were assessed at baseline, 48-72 hours post-surgery, and at 6- and 12-month follow-ups. Pain intensity at rest, movement-evoked pain intensity, and pain unpleasantness were assessed daily in hospital. Memories for pain were elicited via telephone one-year post surgery. Findings revealed that children who had higher levels of anxiety at baseline and 48-72 hours post-surgery developed greater negatively biased recall of pain intensity 12 months after surgery. Specifically, higher anxiety sensitivity at baseline and greater tendencies to catastrophize about pain at baseline and in the immediate acute recovery phase were most strongly linked to greater negatively biased recall of pain. Greater negatively biased recall of pain was related to higher pain intensity at 6- and 12-months post-surgery. Findings support conceptual models of anxiety and pain memory biases and can inform intervention efforts to reduce anxiety in the pre- and post-op periods to minimize negative biases in pain memories.

Despite growing interest in the role of stress mediators in pain chronicity, the effects of the stress hormone cortisol on acute pain remain incompletely understood. In a randomized, double-blind, placebo-controlled study with N=100 healthy volunteers, we tested the effects of oral hydrocortisone (20 mg) in two widely-used pain models for the visceral and somatic modality.Salivary cortisol was increased in the hydrocortisone group (time x group: p<.001). For the visceral modality, assessed using pressure-controlled rectal distensions, hydrocortisone decreased the pain threshold from pre- to post-treatment (time x group: p=.011), an effect primarily driven by women (time x sex: p=.027). For the somatic modality, cutaneous heat pain thresholds remained unaffected by hydrocortisone. Hydrocortisone did not alter perceived pain intensity or unpleasantness of either modality. Conditioned pain-related fear in response to predictive cues was only observed for the visceral modality (time x modality: p=.026), an effect that was significantly reduced by hydrocortisone compared ot placebo (time x group: p=.028).This is the first psychopharmacological study to support that acutely increased cortisol enhances pain sensitivity and impairs pain-related emotional learning within the visceral, but not the somatic pain modality. Stress-induced visceral hyperalgesia and deficits in emotional pain-related learning could play a role in the pathophysiology of chronic visceral pain.

The comorbidity between chronic pain and emotional problems has proven difficult to address with current treatment options. This study addresses the efficacy of a transdiagnostic emotion focused exposure treatment ("hybrid") for chronic pain patients with comorbid emotional problems. Adults (n=115) with chronic musculoskeletal pain, functional and emotional problems were included in a two centre, parallel randomized controlled, open label trial comparing this treatment to an active control condition receiving a guided internet delivered pain management treatment based on CBT principles (iCBT). The hybrid treatment (n=58, 10-16 sessions) integrates exposure in vivo for chronic pain based on the fear-avoidance model with an emotion regulation approach informed by procedures in Dialectical Behavior Therapy. The iCBT (n=57; 8 treatment modules) addresses topics such as pain education, coping strategies, relaxation, problem solving, stress and sleep management using standard CBT techniques. Patient-reported outcomes were assessed pre- and posttreatment as well as at a 9-month primary end point. Across conditions, 78% participants completed post-treatment and 81% follow-up assessment. Intent-to-treat analyses showed that the hybrid had a significantly better post-treatment outcome on pain catastrophizing (d=0.39) and pain interference (d=0.63) and significantly better follow-up outcomes on depression (d=0.43) and pain interference (d=0.51). There were no differences on anxiety and pain intensity. Observed proportions of clinically significant improvement favoured the hybrid on all but one comparison, but no statistically significant differences were observed. We conclude that the hybrid emotion focused treatment may be considered an acceptable, credible and efficacious treatment option for chronic pain patients with comorbid emotional problems.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.