Extended overview of the longitudinal pain-depression association: A comparison of six cohorts treated for specific chronic pain conditions

BACKGROUND The aim was to quantify and to compare the associations between longitudinal changes in pain and depression in different chronic pain conditions. METHODS 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. RESULTS 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). LIMITATIONS The construct of the full range of depressive symptoms is not explicitly covered by the SF-36. CONCLUSIONS 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