Single study, big claims: why n=16 matters
The most exciting recent thread in ME/CFS — a selective central norepinephrine deficit — comes from a study of 16 patients, at one centre, using a new composite measure, and it has not been independently replicated (Aregawi et al. (2026)).
That does not make it wrong. It makes it provisional, and it changes how every downstream claim should be read.
What a small single-centre study can do: generate a clean, testable hypothesis; produce a striking pattern (norepinephrine down, dopamine statistically indistinguishable from controls) that is hard to dismiss as simple chance, though it could partly be an artefact of the novel index; and set an agenda.
What it cannot do: establish a disease mechanism, prove causality, or support confident treatment claims. A novel composite index has not been validated against other cohorts; a single centre carries shared-method and shared-population risks; and physical deconditioning can lower norepinephrine without causing symptoms — a confound not eliminated.
Why we still write about it. Because a hypothesis that is specific, measurable, and falsifiable is valuable even when the evidence is thin — provided the thinness is stated every time. In our paper, the environment types (speculation, hypothesis) carry certainty values, and the noradrenergic threads are mostly 0.25–0.40.
The bottom line: “there may be a selective norepinephrine deficit in ME/CFS, and if it replicates, it would tie together effort intolerance, unrefreshing sleep, and a clearance problem.” The “if it replicates” is the operative clause.