Table 1.

Contributions of key stress models.

ANS-HPA emphasis	Model example	Author/Key citation	Primary measures	Core contributions
SNS HPA	Allostasis/Allostatic Load	McEwen (1998, 2007, 2017)	EDA; PEP (SNS) Cortisol (HPA)	Allostasis—expected stress and stress recovery cycle that allows one to return to baseline Proposed four allostatic load (AL) patterns based upon variation in SNS activation or HPA inhibition. Identified AL patterns underly many disease processes via imbalances in the activation (SNS) and inhibition (HPA) wherein the onset of an adult diagnosis is related to long-term immune system wear and tear.
PNS	Polyvagal Theory	Porges (2007); Porges et al. (1996)	RSA or HRV	Identified two PNS vagus nerve branches Offers sequential and hierarchical stages of activation from newer (ventral vagal) to older (dorsal vagal) High PNS activity through HRV measurement associated with better self-regulation and less stress over-reactivity
SNS and PNS	Modes of Autonomic Control	Berntson et al. (1991) Salomon et al. (2000) and Brush et al. (2019)	PEP and HRV PEP and RSA	Proposed nine modes of autonomic control from differing SNS and PNS dynamics—coupled, reciprocal, and uncoupled patterns Found four arousal profile patterns paralleling some patterns within the doctrine of autonomic control—Coactivation and co-inhibition, Reciprocal sympathetic, Reciprocal parasympathetic
SNS and PNS SNS, PNS, and HPA-axis	Adaptive Calibration Model	Del Giudice et al. (2012); Quas et al. (2014)	EDA and RSA PEP, RSA, Cortisol	Originally proposed four patterns of SNS/PNS activity (Sensitive; Buffered; Vigilant; Unemotional) Found six arousal profile patterns in the multi-site study; Moderate reactivity (most common); Parasympathetic-specific reactivity; Anticipatory arousal; Multisystem reactivity; HPA-specific reactivity; Under-aroused

SNS, Sympathetic nervous system; PNS, Parasympathetic nervous system; HPA-axis, Hypothalamic-pituitary-adrenal axis; EDA, Electrodermal activity; HRV, Heart-rate variability; RSA, Respiratory sinus arrhythmia; PEP, Pre-ejection period.