Drug dependence in patients with chronic pain: A retrospective study

Drug dependence, which can exist concurrently with chronic pain, is seen as one of the major causes of rapidly increasing medical expenses. However, drug dependence in patients with chronic pain has not been evaluated. The aim of this study was to identify the risk factors for drug dependence in patients with chronic noncancer pain. This retrospective study included 151 patients with chronic noncancer pain (43 males, 108 females; mean age, 72 years). Low back pain (LBP) occurred in 96 patients, whereas 22 had shoulder pain, 8 had hip pain, and 77 had knee pain. Patients were divided into drug dependence and nondrug dependence groups based on the Severity of Dependence Scale (SDS) scores. Patients with SDS scores ≥5 and <5 were classified into drug dependence and nondrug dependence groups, respectively. All patients completed self-report questionnaires. Factors that predict drug dependence were identified by performing univariate and multivariate analyses. Sixty (40%) of the 151 patients met the SDS criteria for drug dependence. Significant differences were found between patients with and without drug dependence for the LBP, hip pain, number of medications, and for the Numerical Rating Scale, Pain Disability Assessment Scale (PDAS), Hospital Anxiety and Depression Scale, and Pain Catastrophizing Scale (PCS) scores. Multiple regression analysis identified LBP, hip pain, PCS, and PDAS scores as factors related to drug dependence in patients with chronic noncancer pain. Drug dependence tends to differ in patients based on the location of their chronic pain. Pain catastrophizing and disability indicated a greater tendency for drug dependence. Thus, PCS and PDAS scores are useful screening tools for predicting drug dependence in patients with chronic pain.