Multimorbidity in Chronic Overlapping Pain Conditions: From Burden to Integrated Care.

Chronic overlapping pain conditions (COPCs) refer to a set of chronic pain disorders that frequently co-occur and may involve partially overlapping mechanisms. The U.S. National Institutes of Health currently recognizes ten COPCs: fibromyalgia, painful temporomandibular disorders, chronic low back pain, chronic migraine headache, chronic tension-type headache, irritable bowel syndrome, endometriosis, interstitial cystitis/bladder pain syndrome, vulvodynia, and myalgic encephalomyelitis/chronic fatigue syndrome. When multiple COPCs coexist, they are associated with a disproportionate multimorbidity burden, including greater pain, poorer psychological well-being, functional limitations, disability, fatigue, sleep disturbances, diminished quality of life, and increased healthcare utilization. Despite their impact, COPCs remain under-recognized, underdiagnosed, and undertreated. Combining structured literature searches and citation tracking with narrative syntheses, this review examines comorbid relationships, the burden of multimorbidity, and potentially overlapping nociplastic mechanisms. By adopting a multimorbidity-based perspective rather than a one-disease, one-treatment approach, it highlights barriers to care-including limited clinical awareness, under-recognition of additional COPCs, limited mechanistic understanding, and fragmented care-and proposes integrated strategies emphasizing prevention, systematic screening, mechanism-informed assessment, and coordinated, patient-centered multimodal management.