The mechanics beneath chronic complex illness How autonomic gain, sleep failure, central sensitisation, connective-tissue load, immune priming and energy restriction may converge in ME/CFS, Long COVID, fibromyalgia and dysautonomia. MAY 25 l This is the second piece in the Somatica pair. The first article introduced the map: Martial Law of the Soma, the idea that some chronic complex illnesses behave less like one broken part and more like a whole system reorganising around protection. This piece goes underneath that map. It is more technical, but the aim is still translation. I am not trying to replace medical research, diagnose anyone, or claim a final theory of ME/CFS, Long COVID, fibromyalgia, dysautonomia, hypermobility, trauma physiology or neurodivergent burnout. The question here is narrower: How does a body move from flexible regulation into a state where energy, sleep, pain, cognition, circulation and recovery all become unstable together? The answer is unlikely to be one cause. It is more likely to be a coupled system: alarm regulation, autonomic control, sleep maintenance, immune signalling, connective-tissue load, pain processing, metabolism and cognitive modelling all beginning to feed each other. That is the territory of Somatica Mechanistica. The claim, stated carefully The claim is not that ME/CFS, Long COVID, fibromyalgia, POTS, hEDS, trauma physiology and neurodivergent burnout are all the same disease. They are not. The better claim is this: chronic complex illness can sometimes be understood as layered regulatory collapse, where different triggers push the body into overlapping defensive states. In one person, the dominant face may be pain and sensory amplification. In another, it may be orthostatic intolerance and heart-rate instability. In another, it may be post-exertional malaise and low-power collapse. In another, it may be cognitive fog, sleep failure, nausea, migraine, shutdown or functional neurological symptoms. The labels differ because the dominant surface differs. The shared pattern is that the system no longer returns cleanly to baseline. This is why ME/CFS and Long COVID matter together. Komaroff and Lipkin’s review argues that ME/CFS and Long COVID share symptoms and biological abnormalities, while still requiring careful work to separate subtypes and mechanisms [1]. NICE guidance also makes clear that ME/CFS is not simply “fatigue” , but involves post-exertional malaise, unrefreshing sleep, cognitive difficulty and activity intolerance [2]. So the Somatica claim is not: virus → fatigue. It is closer to: trigger → instability → poor recovery → sensitisation → tighter restriction → deeper instability. That is a different model. Evidence posture Before going further, the evidence has to be separated. Some parts are well supported. Some are plausible integrations. Some are speculative and need testing. High confidence means the mechanism is established generally, even if its exact role in every patient differs. Moderate confidence means there is converging evidence, but it may apply to subgroups or require better longitudinal proof. Speculative means the idea is mechanistically useful, but should be treated as a hypothesis rather than an established fact. This matters because chronic illness discourse often collapses in both directions. Either everything becomes vague and psychosomatic, or every interesting mechanism becomes treated as proven. Both are bad. The useful middle is: strong enough to investig