Researchers found “striking biological similarities” between 5 illnesses once viewed as separate: ME/CFS, Long COVID, PTSD, Rheumatoid arthritis and MS. Despite different triggers—viral infection, trauma or autoimmune responses—they share fatigue, brain fog, poor sleep and autonomic dysfunction. Source: https://www.uea.ac.uk/about/news/article/scientists-uncover-shared-biology-behind-profound-fatigue-in-five-major-illnesses Study: https://link.springer.com/article/10.1186/s12967-026-08874-9