Pain memory in patients with chronic pain versus asymptomatic individuals: A prospective cohort study.

Abstract

The main objective of this study was to assess pain memory as well as long-term episodic memory, both in patients with chronic pain (CP) and in asymptomatic participants (AP). A prospective cohort study design was used. Sixty-eight participants were divided into two groups: CP (n=34) and AP (n=34). The protocol consisted of taking eight tests, four painful provocation tests and four distracting tests, and completing a memory test on the order of the tests at the end of the experiment and at 1-month post-experiment. Patients with CP showed acceptable concordance in the classification, in ascending order from lower to higher pain perception, both post-experiment and 1-month post-experiment (κ=0.41-0.60, p<.001). No differences were found regarding recall of the order of the tests, but differences were found in painful tests isolated only post-experiment in the CP group with a moderate effect size (p<.05, d=0.77). Patients with CP had a more reliable memory than AP in relation to the memory of the pain caused experimentally until at least 1month after the experiment. Interspersing distraction tests appeared to result in increased complexity and difficulty in coding and decoding information in patients with CP, leading to similar reliable long-term memory consolidation in comparison with AP. Treatments directed towards chronic pain should consider the influence of painful memories and their establishment towards long-term explicit episodic memories in patients with chronic pain, as well as the influence of cognitive-evaluative and affective-motivational variables on memory. Not causing pain while implementing a treatment whose objective is to reduce pain could reduce the probability of developing new painful memories in patients with chronic pain.