(427) Could depression be a causative factor in the development of CRPS types I?

CRPS (Complex regional pain syndrome) is a debilitating pain disorder characterized by allodynia, hyperalgesia and trophic changes. It has been sub classified into CRPS type I and type II. While CRPS type II is considered to be caused by a prior nerve injury, CRPS type I, also known as reflex sympathetic dystrophy is a poorly understood medical condition with no definitive identifiable etiology. Studies have shown that patients with depression have an increased rate of having chronic pain, including CRPS. These patients also have poorer outcomes of recovery. No trials have however analyzed the differences in rates of depression between CRPS types I and II. The aim of our study was to identify whether depression could be an etiological factor in patients with CRPS type I. For this study, we consulted the Nationwide Inpatient Sample (HCUP) database between 2003 and 2011 and compared the incidence of depression between CRPS type I and II patients. Overall 95637 patients were found to have CRPS type I and 5012436 patients had CRPS type II. Of these patients 21% and 9.9% respectively had depression. The rate of depression was significantly higher amongst patients with CRPS type I vs. CRPS type II (P= < 0.001). Since patients with CRPS type I by definition have no known nerve injury, it may suggest depression as a causative agent for this disease. Our study is limited due to paucity of data and we have therefore not been able to analyze other confounding factors. A comprehensive retrospective chart analysis is needed for patients with CRPS type I to identify the validity of this study.