Many people are confronted with chronic pain that can last for months or even years. How to best treat chronic pain? First, pain must be categorized for the right treatment to be prescribed. However, is that it is very challenging for patients to define their pain, its intensity or even its location using questionnaires. To overcome this difficulty, scientists from the University of Geneva (UNIGE) have joined forces with the research department of the Clinique romande de réadaptation (CRR) in Sion to carry out a complete epigenomic analysis of patients, making it possible to find the epigenetic signatures specific to each pain category. Thus, a simple blood test would make it possible to define which pain the person suffers from and, in the future, to prescribe treatment accordingly and to observe whether the biomarkers modified by the pain return to normal. These results can be read in the Journal of Pain.