Can PTSD and chronic traumatic stress keep stress systems activated?

Chronic traumatic stress and PTSD systematically alter neurobiology, permanently shifting the basal set-points of key survival networks.

Autonomic and endocrine dysregulation

• Sympathetic hyperarousal: Chronic stress maintains sympathetic nervous system (SNS) hyperarousal, characterized by elevated catecholamines and reduced heart rate variability (specifically lower RMSSD and high-frequency HRV), which indicates diminished parasympathetic vagal tone.
• HPA axis dysregulation: Rather than classic hypercortisolism, individuals often exhibit relative hypocortisolism (low basal morning or 24-hour cortisol) and enhanced glucocorticoid sensitivity, as demonstrated by "super-suppression" during dexamethasone testing. This prevents the normal physiological "brake" on cortisol-releasing hormone (CRH) and norepinephrine.

Mechanistic pathways to somatic symptoms

• Cardiorespiratory and sleep disruptions: Chronic sympathetic tone stimulates cardiac $\beta$-adrenergic receptors to cause palpitations, while nocturnal cortisol and catecholamine elevation disrupt sleep architecture, driving insomnia and fatigue.
• Gastrointestinal and immune pathways: Elevated CRH and autonomic imbalance alter motility—slowing gastric emptying while accelerating colonic transit—and increase intestinal tight junction permeability. This barrier compromise, paired with sympathetic drive, upregulates pro-inflammatory cytokines such as IL-6 and TNF-$\alpha$.
• Self-reinforcing feedback loops: Systemic inflammation and sleep disruption cross the blood-brain barrier to act as endogenous stressors, further compounding HPA axis overactivation and sympathetic hyperarousal in a self-sustaining cycle.

Bottom line

• Strong scientific evidence confirms that chronic trauma drives a bidirectional stress-hyperarousal-gut-brain loop, where sustained HPA and sympathetic activation generate insomnia, palpitations, gastrointestinal distress, and inflammation, which then feed back to perpetuate autonomic and endocrine dysregulation.