Comparison of psychiatric comorbidity in treatment-seeking, opioid-dependent patients with versus without chronic pain

Aim To compare psychiatric morbidity in treatment-seeking, opioid-dependent patients with versus without chronic pain. Design A retrospective comparative cohort design was used involving record linkage from routinely collected, nationally held data sets. Data were managed within a Scottish Government-certified Safe Haven. Setting and participants Participants comprised all patients of an NHS Substance Misuse Service in the East of Scotland (n = 467) who were in treatment during 2005 and had been in treatment for varying lengths of time. Their mean age at study inception was 35.0 years in the chronic pain group and 32.1 years; 68% of the chronic pain group and 74% of the no pain group were male. Measurements The outcomes were (a) psychiatric comorbidity assessed at study inception using the 28-item General Health Questionnaire and the Clinical Outcomes in Routine Evaluation-Outcome Measure and (b) receipt of at least one prescription for a psychiatric condition during a 5-year period following study inception. The independent variable was chronic pain measured at study inception using the Brief Pain Inventory-Short Form. Findings A total of 246 (52.7%) reported chronic pain and 221 (47.3%) did not. A higher proportion of patients with chronic pain had at least one psychiatric morbidity (62.4 versus 46.3%, P < 0.001). At the study inception, a higher proportion of patients with chronic pain were prescribed anxiolytics (49.0 versus 39.1%, P = 0.015) and antimanic drugs (9.9 compared with 4.9%, P = 0.015). Conclusions Patients of opioid treatment services in Scotland who report chronic pain may have a higher prevalence of psychiatric comorbidity than those who do not.