1. 2023;26;E1-E49The Prevalence of Perceived Injustice and Factors Associated With Perceived Injustice in People With Pain: A Systematic Review With Meta-analysis
   Systematic Review
   Annick Timmermans, PhD, Marijke De Couck, PhD, David Beckwee, MSc, Paul van Wilgen, PhD, Jo Nijs, PhD, Eva Huysmans, MSc, Kenza Mostaqim, MSc, Ella Smout, BS, Anke Robbeets, BS, Astrid Lahousse, MSc, Eva Roose, MSc, Rinske Bults, MSc, and Laurence Leysen, PhD.

BACKGROUND: Perceived injustice (PI) is a multidimensional appraisal cognition comprising the severity of loss consequent to injury, blame, a sense of unfairness, and/or irreparability of loss. PI gained increasing interest in pain research since it potentially contributes to the experience and burden of (chronic) pain.

OBJECTIVES: This systematic review aimed to determine the prevalence of PI and factors associated with PI in people with pain.

STUDY DESIGN: Systematic review with meta-analysis.

METHODS: Web of Science, PubMed, and Embase were screened for cross-sectional or cohort studies encompassing human patients who were diagnosed with a condition causing pain and reported prevalence rates for PI and/or associations between a factor and PI. Meta-analyses were carried out, and subgroup analyses were undertaken based on the methodological quality of the studies, the type of pain population, and whether the outcome measure was valid or not in case of heterogeneity (P < 0.05).

RESULTS: Fifty-four studies were found eligible. The prevalence of PI ranged from 23% to 77% (I2 = 99%, P < 0.001). Association with PI, assessed using the Injustice Experienced Questionnaire, were found with pain catastrophizing (pooled Pearson’s r [rp] = 0.66 [0.64, 0.69], P < 0.00001), posttraumatic stress (rp = 0.63 [0.59, 0.67], P < 0.00001), anger (rp = 0.59 [0.49, 0.67], P < 0.00001), anxiety (rp = 0.59 [0.52, 0.64], P < 0.00001), pain acceptance (rp = -0.59 [-0.66, -0.49], P < 0.00001), depressive symptoms (rp = 0.57 [0.52, 0.60], P < 0.00001), kinesiophobia (rp = 0.57 [0.50, 0.64], P < 0.00001), academic functioning (rp = -0.54 [-0.65, -0.41], P < 0.00001), disability (rp = 0.53 [0.47, 0.59], P < 0.00001), emotional functioning (rp = -0.52 [-0.64, -0.39], P < 0.00001), pain interference (rp = 0.49 [0.35, 0.60], P < 0.00001), state anger (rp = 0.48 [0.41, 0.54], P < 0.00001), mental functioning (rp = -0.48 [-0.57, -0.38], P < 0.00001), symptoms of central sensitization (rp = 0.47 [0.39, 0.55], P < 0.00001), social functioning (rp = -0.47 [-0.60, -0.31], P < 0.00001), and physical functioning (rp = -0.43 [-0.53, -0.33], P < 0.00001), pain perceptions (rp = 0.40 [0.40, 0.64], P < 0.00001), trait anger (rp = 0.40 [0.29, 0.49], P < 0.00001), pain intensity (rp = 0.37 [0.33, 0.42], P < 0.00001), and anger inhibition (rp = 0.35 [0.26, 0.43], P < 0.00001).

LIMITATIONS: Some articles had to be excluded due to the absence of a full-text version. The findings can largely be applied to developed and high-income countries, but further research is needed in developing countries. Also, no validated cutoff values were available for the National Institutes of Health to determine the methodological quality of the included studies. Lastly, high heterogeneity was observed in many of the performed analyses. However, this was addressed by performing subgroup analyses, which could decrease heterogeneity in some cases.

CONCLUSIONS: The prevalence of PI was >= 33% in 75% of the studies indicating that PI is important to consider in people with pain. There is evidence for the association of PI with psychological, pain, and quality of life characteristics in people with pain. The associations of PI with personal, injury, and recovery characteristics were overall not significant or negligible.

KEY WORDS: Pain, perceived injustice, psychological, quality of life, prevalence, association, systematic review, meta-analysis