What it isA state of chronically elevated physiological and psychological arousal — including elevated heart rate, heightened threat sensitivity, and inability to relax — that persists even in the absence of current threat. The hallmark physiological state of PTSD and primary insomnia.

Why it mattersHyperarousal is the central mechanism that disrupts sleep in veterans with PTSD and combat insomnia. It keeps the nervous system on alert during sleep, fragmenting sleep architecture and preventing the restorative depths of slow-wave and REM sleep that the brain requires.

Think of it like thisHyperarousal is a car alarm that stays triggered long after the threat has passed. The system is calibrated to respond to danger and hasn’t received the signal to stand down.

A neurobiological state characterized by elevated activity in the hypothalamic-pituitary-adrenal axis, locus coeruleus-norepinephrine system, and amygdala, producing sustained sympathetic nervous system activation, elevated physiological arousal markers, and reduced threshold for threat response. Distinct from acute stress response in being persistent and stimulus-independent.

MechanismHyperarousal is maintained by: (1) HPA axis hypersensitivity producing elevated cortisol and CRH; (2) locus coeruleus sensitization producing chronic NE elevation; (3) amygdala hyperreactivity to threat cues with reduced prefrontal inhibition. During sleep, these systems fail to downregulate, preventing entry into slow-wave and REM sleep and producing the characteristic fragmented sleep architecture of PTSD and primary insomnia.