Ten-year prevalence of mental disorders in patients presenting with chronic pain in secondary care: A register linkage cohort study

Background: Prevalence rates of mental disorders in patients with chronic pain vary and may be overestimated when assessed by screening instruments only. Objectives were to estimate the 10-year prevalence of different mental disorders diagnosed by psychiatrists in patients with chronic pain compared with the Danish general population. Methods: Patients (n = 7197) consulted in the interdisciplinary Pain Clinic South at Odense University Hospital, Denmark, from 2005 to 2015 were included. Data from the Pain Clinic were linked to the Danish National Patient Register-Psychiatry and the Danish Civil Registration System. Age and gender standardized prevalence ratios (SPR) were calculated. Results: In all, 17.8% of patients with chronic pain had been diagnosed with a mental disorder. The most frequent diagnoses were adjustment disorders (subcategory of anxiety disorders) (8.9%), depression (6.1%), personality disorders (3.8%), and substance abuse disorders (3.5%). Women and men with chronic pain had higher rates of anxiety disorders (SPR 3.1; 95% CI 2.9–3.4) and depression (SPR 2.5; 95% CI 2.3–2.8), whereas men had higher rates of substance abuse disorders (SPR 1.6; 95% CI 1.3–1.9) than found for the general population. Conclusions: Although depression and anxiety were noted more frequently among patients with chronic pain than the general population, prevalence rates were lower than previously reported. The most frequent diagnoses were adjustment disorders. Significance: Prevalence rates of anxiety and depression diagnosed by psychiatrists in patients with chronic pain were found to be lower than previous findings using screening instruments. Adjustment disorders were the most frequent disorders diagnosed, as this study is the first to investigate.