 Criticisms of Dr. Apkarian's work include his focus on chronic low back pain, low rates of depression in his clinical cohorts, and emphasis on cortical mechanisms of chronic pain.Nevertheless, his use of rigorous statistical analyses, validation of findings in independent cohorts, replication of findings using multiple imaging modalities, use of longitudinal neuroimaging, and replication of key fMRI findings in rodent models of neuropathic pain have created a consistent body of research.Chronic pain is one of the biggest health problems in the world.