The aim was to quantify and to compare the associations between longitudinal changes in pain and depression in different chronic pain conditions.
Data were retrieved from 6 observational cohort studies. From baseline to the 6-month follow-up, the score changes on the Short Form (36) Health Survey (SF-36) bodily pain (pain) and the SF-36 mental health (depression) scales (0=worst, 100=best) were quantified, using partial correlations obtained by multiple regression. Adjustment was performed by age, living alone/with partner, education level, number of comorbidities, baseline pain and baseline depression.
Stronger associations were found between changes in levels of pain and depression for neck pain after whiplash (n = 103, mean baseline pain=21.4, mean baseline depression=52.5, adjusted correlation r = 0.515), knee osteoarthritis (n = 177, 25.4, 64.2, r = 0.502), low back pain (n = 134, 19.0, 49.4, r = 0.495), and fibromyalgia (n = 125, 16.8, 43.2, r = 0.467) than for lower limb lipedema (n = 68, 40.2, 62.6, r = 0.452) and shoulder arthroplasty (n = 153, 35.0, 76.4, r = 0.292). Those correlations were somewhat correlated to baseline pain (rank r=-0.429) and baseline depression (rank r=-0.314).
The construct of the full range of depressive symptoms is not explicitly covered by the SF-36.
Moderate associations between changes in pain and depression levels were demonstrated across 5 of 6 different chronic pain conditions. The worse the pain and depression scores at baseline, the stronger those associations tended to be. Both findings indicate a certain dose-response relationship – an important characteristic of causal interference. Relieving pain by treatment may lead to the relief of depression and vice versa.

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