OPRM1 and Chronic pain: These analyses have identified upregulation of genes related to neuroinflammation (e.g., TNF, IL1B, CCL2), neuronal excitability (e.g., SCN9A, TRPV1, CACNA1H), and neuromodulatory signaling (e.g., BDNF, TAC1, OPRM1) in patients with various chronic pain phenotypes, including fibromyalgia, neuropathic pain, and chronic low back pain.