Wired but tired: arousal that won’t switch off
“Wired but tired” is one of the most common descriptions patients give — and one of the least examined. You are exhausted, but your system will not stand down. You cannot fall asleep, or cannot relax, even when you have no energy left.
It is easy to file this under “insomnia” or “anxiety.” A more specific idea is that it is an arousal-mismatch: the system that switches arousal on and off cannot make the transition it should.
Norepinephrine is one of the brain’s main arousal switches. If its output is low — and, plausibly, poorly regulated (the dysregulation is not measured in ME/CFS) — the system may fail to shut arousal off at the right time, producing the exhausted-but-hyperaroused state (Osorio-Forero et al. (2021); Lüthi and Nedergaard (2025)).
This is distinct from the sleepiness state in the “four flavors of fatigue” framing. There, a person cannot sleep because they are genuinely not sleepy. Here, they are profoundly tired yet unable to switch off.
We should be careful. “Wired but tired” is not proof of a norepinephrine lesion. Hyperarousal can also come from inflammatory cytokines, a dysregulated stress (HPA) axis, anxiety, or sensory hypersensitivity. So this is a candidate, not a diagnosis.
How to test it. If it is an arousal-transition failure, then measures of arousal control — pupil dynamics, sleep-onset latency with preserved sleep pressure — should differ in patients who report the pattern, and should track the norepinephrine pathway. That is a testable prediction.
Why it matters: giving a common, dismissed experience a mechanism makes it something research can study — and takes it out of the “it’s just anxiety” bucket.