The loop that could keep ME/CFS going
Many chronic illnesses are described as “self-reinforcing,” but a loop is only a serious idea if you can name the arrows. Here is one candidate, built on the arousal system.
Norepinephrine drives slow vasomotion — the rhythmic squeezing of blood vessels — that pumps cerebrospinal fluid through the brain and clears waste during sleep; this has been shown in mice (Hauglund et al. (2025)). The 2026 Science review of sleep oscillations describes neuromodulators as the mechanical force behind this clearance (Nedergaard (2026)).
Now the loop:
- Central norepinephrine falls.
- Vasomotion weakens, so clearance falls.
- Metabolic waste and inflammatory signals accumulate.
- Neuroinflammation impairs locus-coeruleus function.
- Norepinephrine falls further. Back to step 1.
If that loop exists, ME/CFS is not a fixed deficit but a system that can slowly ratchet downward — progression better described as a loop tightening than as simple cumulative damage.
What supports it, and what does not. The norepinephrine-to-clearance arrow has real evidence (animal and review level). The clearance-to-inflammation-to-locus-coeruleus arrows are inferred; they have not been measured in ME/CFS.
Where the evidence is unsettled. The loop’s inflammation-to-locus-coeruleus arrow assumes that norepinephrine suppresses neuroinflammation. Two mouse studies largely support that: norepinephrine acting on microglial β2 receptors suppressed microglial activity (Bu et al. (2025)), and inhibiting locus-coeruleus adrenergic signalling increased neuroinflammation (Evans et al. (2024)). But a sub-analysis of the second study found that deleting the β2 receptor in microglia reduced inflammation in females only — so the direction is not fully settled and may be sex- or context-dependent. The loop is a hypothesis, not a claim.
As throughout this series, the underlying deficit is a single unreplicated finding (Aregawi et al. (2026)). Why it matters: if a loop drives progression, then treating one node (say, norepinephrine alone) may not be enough; the loop may need to be broken at more than one point.