Vagus nerve & stress
12th Oct, 2021

Vagus Nerve and Sress


Chronic stress can affect physical and psychological wellbeing by causing various problems, including anxiety, insomnia, high blood pressure, inflammation, and a weakened immune system. The consequences of chronic stress are serious and can lead to chronic diseases such as cardiovascular disease, depression, and obesity (1).

The vagus nerve, a cranial nerve that connects the brain to many body systems, plays a crucial role in the stress response via the autonomic nervous system (ANS) and the microbiota-gut-brain axis (2). Therefore, supporting healthy vagus nerve activity can improve resiliency to and recovery from physiological and psychosocial stress, improve emotional regulation and lead to better physical and mental health and wellbeing.

Electrical and transcutaneous vagal nerve stimulation methods are now used for treating conditions such as epilepsy and depression (3). However, there are simple and sustainable ways to improve stress resiliency, health and wellbeing by improving vagal tone. 


Vagus nerve structure and function

The vagus nerve, the largest and most complex of the twelve cranial nerves, is actually a set of nerves connecting most of the major organs between the brain and the gastrointestinal tract (4).

The word vagus is Latin for wanderer (5). As the name implies, the nerve branches numerous times from its origins in the medulla oblongata in the brain and projects to major visceral organs, including the heart, lungs, and gastrointestinal tract, independent of the spinal column (5).

The vagus nerve relays signals from the brain to the body (efferent) and the visceral organs to the brain (afferent). Physiologically, it plays a critical role in sensory, motor, and parasympathetic functions. These include the inflammatory response, respiration, digestion, heart rate, food intake and satiety, swallowing and speech (2,5).

The vagus nerve is often described as the mind-body connection because it provides a major neural connection between the gut and brain and plays a crucial role in facilitating signalling along the microbiota-gut-brain axis (5,6). The vagus nerve can sense microbial metabolites through its afferent fibres and transfer this gut information to the central nervous system (CNS), where it is integrated into the central autonomic network to generate a physiological or behavioural response (6).

One of the most important roles of the vagus nerve is regulating the parasympathetic nervous system (PNS) (rest-and-digest response), which acts as a counterbalance to the sympathetic nervous system (fight-or-flight response). To achieve this, efferent vagal neurons release acetylcholine into various organs, which helps facilitate blood pressure regulation, heart rate, respiration, and digestion to promote rest, repair, and growth (2,5). The vagus nerve is therefore essential for promoting a healthy stress response and enhancing physical and mental resilience.


Figure 1 Overview of the anatomy and functions of the vagus nerve and related disorders. Adapted from (5) CC BY

Vagus Nerve and stress Figure 1


Vagal tone and its effects on physical and emotional health

The activity of the vagus nerve is referred to as vagal tone, and a healthy vagal tone supports the ability of the PNS to counterbalance the SNS. Individuals with a higher vagal tone can regulate bodily functions more readily, including respiration, metabolism, and cardiac activity, than those with low vagal tone (2,5).

The time interval between successive heartbeats, called heart rate variability (HRV), is often used to indicate vagal tone. Higher efferent vagal activity triggers neurons projecting to the heart's sinoatrial node to release acetylcholine, thereby decreasing heart rate, and increasing HRV (7). Individuals with high resting HRV (i.e. high vagal tone) have been shown to have more rapid recovery in their cardiovascular, immune and endocrine responses to stress (8,9).

In contrast, low HRV (i.e. low vagal tone) is considered a marker of sensitivity to stress. Low HRV has been associated with impaired stress response, inflammation, deregulation of glucose metabolism and the hypothalamic-pituitary-adrenal (HPA) axis (10,11). Furthermore, low HRV has been linked to impaired neural activity in the prefrontal and limbic regions of the brain, which are involved in emotional and cognitive functioning (11,12).

Accumulating evidence reveals the link between vagal tone and physical and emotional health and wellbeing. For example, low vagal tone has been associated with a range of chronic health conditions, including migraine headaches, inflammatory bowel disease, epilepsy, arthritis, and cardiovascular disease (6,13,14). Furthermore, it has also been associated with depression, post-traumatic stress disorder (PTSD), loneliness, negative feelings, and poor emotional regulation.  In contrast, individuals with a higher vagal tone have more effective regulation of emotional responses, strong social connections, positive emotions, and better physical health (15,16).


Vagal nerve stimulation

Vagus nerve stimulation can be employed to increase the tone of the vagus nerve. It was first identified in the late 19th century when it was noted that epileptic seizures could be suppressed by massage of the carotid artery in the cervical region of the neck due to stimulation of the vagus nerve (17). 

Vagal nerve stimulation using implanted electrical devices in the chest has been used for more than 20 years to control seizures in epilepsy patients and has been approved for treating drug-resistant cases of clinical depression (18). It is also used in chronic heart failure (19). More recently, non-invasive vagus nerve stimulation devices that do not require surgical implantation (transcutaneous vagus nerve stimulation (tVNS)), have been approved for treating epilepsy (20), pain (21), depression (22), and migraines (23,24).

Currently, because of its influence on the immune system, researchers are investigating the vagus nerve’s role in treating inflammatory disorders such as traumatic brain injury (25), sepsis and  lung injury (26), diabetes (27) and autoimmune conditions including rheumatoid arthritis (28,29), systemic lupus erythematosus (SLE) (30,31) and Crohn’s disease (32,33).


Natural ways to stimulate the vagus nerve

Apart from electrical and transcutaneous vagal nerve stimulation, there are natural ways to stimulate the vagus nerve and improve and rebalance the function of the ANS, which can have significant physiological and psychological health benefits including:

  • Greater emotional stability
  • A sense of calm and wellbeing
  • Improved digestion and motility
  • Reduced inflammation
  • Improved ability to deal with stress
  • Reduced loneliness
  • Deeper relationship connections
  • Reduced pain sensitivity.


Mind-body interventions

Slow breathing exercises

Controlled, slow breathing or diaphragmatic breathing has been demonstrated to be an effective means of preserving autonomic function and has been associated with benefits for numerous conditions, including anxiety, depression, PTSD, pain, insomnia, hypertension, asthma, and chronic obstructive pulmonary disease (COPD) (34,35). 

Vagus nerve activity is modulated by respiration. It is supressed during inhalation and facilitated during exhalation and slow respiration cycles (36). The SNS facilitates a brief heart rate acceleration during the inhalation phase of a breathing cycle. During exhalation, the vagus nerve secretes the neurotransmitter acetylcholine. This release causes the heart rate to slow via the PNS and promotes a state of relaxation (37).

Typically, the breathing techniques used in contemplative activities such as yoga, meditation and tai chi include longer exhalations compared to inhalations (diaphragmatic breathing). Diaphragm breathing at six breaths a minute has been found to optimise the balance between the two branches of the ANS (38), making the system better able to adapt to both physical and mental stress.

Several clinical trials have demonstrated the positive effects of slow breathing on vagal activity, with a respiratory rate of 6 breaths/minute, reducing HRV and blood pressure (39,40,41).

Singing or chanting

The vagus nerve is connected to the vocal cords and the muscles at the back of the throat. Singing, humming, chanting, and gargling can activate these muscles and stimulate the vagus nerve. Furthermore, singing requires a slower than normal respiration which may, in turn, affect heart rate (42).

Om chanting is a meditation technique and an important exhalation exercise used in yoga, mantras, and different faiths such as Hinduism and Buddhism. Effective Om chanting causes a vibrating sensation around the ears, which is transmitted through the auricular branch of the vagus nerve, stimulating the vagal nerve (43) and deactivating the limbic system (44).

By increasing parasympathetic activity and reducing SNS activity, Om chanting has been found in clinical trials to reduce hypertension (45), alleviate menopausal symptoms (46), improve pulmonary function in healthy individuals (47) and reduce anxiety (48), depression and stress (49).


Meditation is a conscious mental process that induces a set of integrated physiologic changes involved in the relaxation response. Studies suggest that at least three types of meditation may stimulate the vagus nerve indirectly. In small studies, loving-kindness meditation, mindfulness meditation, and Om chanting increased HRV (44,50). Some researchers think that conscious, deep breathing that accompanies meditation and other contemplative practices might underlie this effect (50).


Mindfulness is a well-established technique for developing the ability to self-regulate attention and emotion. Specifically, mindfulness can be defined as the cognitive ability to pay attention to the present moment without judgment or attachment to a desired outcome (51). Benefits of mindfulness include reduced pain and stress, improved cognitive functioning, increased positive emotion, and emotional regulation (51).

Several recent studies have provided preliminary evidence for mindfulness practice and its association with the increased parasympathetic tone, including increased HRV response (52,53). Furthermore, long-term mindfulness retreats have been shown to increase HRV (54). The increases in HRV and dominance of the PNS during mindfulness may partly be caused by changes in respiration which are modulated by the vagus nerve, since awareness of breathing is central to mindfulness practice (55,56).


Numerous studies have shown the effect of various yoga practices for depression and anxiety (57,58), inflammatory conditions (59) and stress (60,61).

Yoga is known to exert its health benefits through several mechanisms of action including increasing neurotransmitter synthesis and neurotrophic factors, anti-inflammatory effects, HPA axis modulating effects (62) and effects on the vagus nerve (63).

A review of 59 studies with 2,358 participants suggested that yoga can affect autonomic regulation with increased HRV and vagal dominance during yoga practices. Regular yoga practitioners were also found to have increased vagal tone at rest compared to non-yoga practitioners. However, most studies were of poor quality, with small sample sizes, and insufficient reporting of study design and statistical methods and further rigorous studies with detailed reporting of yoga practices are required to determine the effect of yoga on HRV and vagal tone (63).

 Autonomous Sensory Meridian Response

Autonomous Sensory Meridian Response (ASMR) is an experience of calm and tingles, a tingling sensation like electricity radiating from the head and neck, which affects the ANS. ASMR experiences are caused by a stimulus or trigger which is usually an audio-visual stimulus and entails whispering, scratching, tapping and other noises (64). A recent study of university students found significant differences in heart rate and systolic and diastolic blood pressure occurred after watching a 3-minute ASMR video (65). Further rigorous studies are required to assess the effect of ASMR on vagal tone.


Several studies have shown an association between laughter, mood, and better health (66), with researchers attributing some of its benefits to effects on the vagus nerve. In a pilot study, yoga laughter therapy for 4 weeks improved mood and increased HRV in patients awaiting organ transplantation (67). Furthermore, laughter is also sometimes a side effect of chronic vagus nerve stimulation performed in children with refractory epilepsy (68).


Positive emotions and positive social connections

Social isolation has a negative impact on mental, physical, and emotional health and overall mortality (69). A meta-analysis including 148 studies (308,849 participants) showed a 50% increased likelihood of survival for participants with stronger social relationships. Furthermore, the influence of social relationships on mortality risk is comparable with well-established risk factors for mortality, such as smoking (69). 

Several studies demonstrate that positive social interactions affect HRV. For example, one study of 2066 male civil servants in the United Kingdom (the Whitehall cohort) found a correlation between lower HRV and low social integration (70).

A randomised controlled trial demonstrated that compared to a control group, participants who undertook 6 weeks of loving-kindness meditation were able to self-generate positive emotions and improve vagal tone, which was mediated by increased perception of social connections (71).

One mechanism by which social isolation may negatively impact health outcomes is via altered ANS function. For example, a lower HRV has been correlated with adverse health outcomes, including reduced cognitive function, depression, cardiovascular disease, and all-cause mortality (72).



Aerobic exercise

During moderate-to-vigorous physical exercise (e.g. cycling, running, swimming, rowing), SNS activity and adrenaline production increases, elevating heart rate, blood pressure, and breathing rate above basal levels and concurrently, vagal control drops. However, after exercise, vagal control (measured as HRV) rises again, as the PNS and SNS branches of the ANS interact to restore heart rate to its baseline value (73,74).

Research indicates that regular physical exercise of moderate intensity can increase vagal tone (i.e., during rest) and vagal control (i.e. in response to a stressor) (75). Compared to sedentary controls, athletes have increased cardiac vagal tone as assessed with HRV (76). In addition, clinical trials demonstrate that regular aerobic exercise can significantly change HRV parameters that indicate enhanced vagal tone in sedentary adults (77).

Resistance training

Several clinical studies provide evidence that resistance training improves HRV in COPD (78), coronary artery disease (79) and obesity (80).




The vagus nerve's role in the microbiota-gut-brain axis is now well established; thus, therapies targeting the microbiota may positively affect vagal activity (6).

Animal studies have looked at the potential effects of probiotics on the vagus nerve, but human clinical trials are still lacking. Two studies found positive effects of L. rhamnosus and B. longum that were mediated via the vagus nerve (i.e. no effect in vagotomised mice) (81,82) and one study found that L. casei Shirota enhanced gastric vagal afferent activity (83). L. rhamnosus (JB-1) reduced stress-induced corticosterone and anxiety- and depression-related behaviour and induced positive changes in GABA receptors that were mediated by the vagus nerve (81). 

Omega- 3 fatty acids

A growing number of studies have shown an increase in HRV and lower heart rate with higher fish intake or omega-3 fatty acid supplements (84,85,86,87).

In a study of obese children and adolescents at risk of developing cardiovascular disease, supplementation with fish oil (containing at least 400 mg eicosapentaenoic acid (EPA) and 120 mg docosahexaenoic acid (DHA) daily) over at least 3 months reduced HRV compared to healthy controls (84).

In a population-based cross-sectional study, increased fish consumption was significantly correlated with several HRV indices indicative of higher parasympathetic activity (88).


Intermittent fasting and reducing calories both increase HRV in animal studies (89). Several human clinical trials demonstrate caloric restriction and weight loss are associated with increased HRV, and improved SNS/PNS balance (90,91).


Other interventions

Cold exposure

Acclimation to cold (10°C) has been shown to lower sympathetic activation and cause a shift toward increased parasympathetic activity (92). Studies have shown that following exercise, submersion to mid-sternal level in cool (14–15°C) (93) or facial immersion in cold water (10–12°C) (94) led to greater reactivation of the parasympathetic system as assessed by HRV indices.

This effect can be achieved by drinking cold water, dipping the face in cold water, or taking cold showers.


Many massage techniques have been shown to increase HRV/vagal tone including traditional Thai shoulder, neck, and head massage (95), traditional Thai back massage (96), Chinese head massage (97), and foot massage (98).

Self-massage of trigger points in the upper neck has been shown to increase HRV in patients with myofascial pain dysfunction syndrome (99).

Moderate pressure massage in underweight babies may assist with weight gain via increased vagal activity, which, in turn, stimulates gastric motility (100).



  • The vagus nerve connects the brain to many organs throughout the body, including the gut. It plays a crucial role in the stress response via the autonomic nervous system (ANS) and the microbiota-gut-brain axis.
  • Heart rate variability (HRV) measures vagal tone (or activity) and is considered a marker of sensitivity to stress.
  • Low HRV has been associated with inflammation, impaired stress response, depression and other chronic health conditions. 
  • Electrical and transcutaneous vagal nerve stimulation has been approved for the treatment of refractory epilepsy and depression. 
  • There are many simple ways to stimulate the vagus nerve to support the ANS and promote psychological and physical health and wellbeing. These include mind-body interventions, exercise, nutrition, social connection and cold exposure.
1Mariotti A. The effects of chronic stress on health: new insights into the molecular mechanisms of brain-body communication. Future Sci OA. 2015 Nov 1;1(3):FSO23.
2Dedoncker J, Vanderhasselt MA, Ottaviani C, Slavich GM. Mental health during the COVID-19 pandemic and beyond: The importance of the vagus nerve for biopsychosocial resilience. Neuroscience & Biobehavioral Reviews. 2021 Feb 11;125:1-10.
3Bremner JD, Gurel NZ, Wittbrodt MT, Shandhi MH, Rapaport MH, Nye JA, Pearce BD, Vaccarino V, Shah AJ, Park J, Bikson M. Application of noninvasive vagal nerve stimulation to stress-related psychiatric disorders. Journal of Personalized Medicine. 2020 Sep;10(3):119.
4Yuen AW, Sander JW. Can natural ways to stimulate the vagus nerve improve seizure control?. Epilepsy & Behavior. 2017 Feb 1;67:105-10.
5Breit S, Kupferberg A, Rogler G, Hasler G. Vagus nerve as modulator of the brain–gut axis in psychiatric and inflammatory disorders. Frontiers in psychiatry. 2018 Mar 13;9:44.
6Bonaz B, Sinniger V, Pellissier S. The vagus nerve in the neuro-immune axis: implications in the pathology of the gastrointestinal tract. Frontiers in immunology. 2017 Nov 2;8:1452.
7Burger AM, Verkuil B. Transcutaneous nerve stimulation via the tragus: are we really stimulating the vagus nerve?. Brain stimulation. 2018 Apr 5;11(4):945-6.
8Kaniusas E, Kampusch S, Tittgemeyer M, Panetsos F, Gines RF, Papa M, Kiss A, Podesser B, Cassara AM, Tanghe E, Samoudi AM. Current directions in the auricular vagus nerve stimulation I–a physiological perspective. Frontiers in neuroscience. 2019 Aug 9;13:854.
9Weber CS, Thayer JF, Rudat M, Wirtz PH, Zimmermann-Viehoff F, Thomas A, Perschel FH, Arck PC, Deter HC. Low vagal tone is associated with impaired post stress recovery of cardiovascular, endocrine, and immune markers. European journal of applied physiology. 2010 May;109(2):201-11.
10Sloan RP, McCreath H, Tracey KJ, Sidney S, Liu K, Seeman T. RR interval variability is inversely related to inflammatory markers: the CARDIA study. Molecular Medicine. 2007 Mar;13(3):178-84.
11Thayer JF, Åhs F, Fredrikson M, Sollers III JJ, Wager TD. A meta-analysis of heart rate variability and neuroimaging studies: implications for heart rate variability as a marker of stress and health. Neuroscience & Biobehavioral Reviews. 2012 Feb 1;36(2):747-56.
12Thayer JF. Vagal tone and the inflammatory reflex. Cleveland Clinic journal of medicine. 2009 Apr 1;76:S23-6.
13Drewes AM, Brock C, Rasmussen SE, Møller HJ, Brock B, Deleuran BW, Farmer AD, Pfeiffer-Jensen M. Short-term transcutaneous non-invasive vagus nerve stimulation may reduce disease activity and pro-inflammatory cytokines in rheumatoid arthritis: results of a pilot study. Scandinavian journal of rheumatology. 2021 Jan 2;50(1):20-7.
14Johnson RL, Wilson CG. A review of vagus nerve stimulation as a therapeutic intervention. J Inflamm Res. 2018 May 16;11:203-213.
15Kok BE, Coffey KA, Cohn MA, Catalino LI, Vacharkulksemsuk T, Algoe SB, Brantley M, Fredrickson BL. How positive emotions build physical health: Perceived positive social connections account for the upward spiral between positive emotions and vagal tone. Psychological science. 2013 Jul;24(7):1123-32.
16Pinna T, Edwards DJ. A Systematic Review of Associations Between Interoception, Vagal Tone, and Emotional Regulation: Potential Applications for Mental Health, Wellbeing, Psychological Flexibility, and Chronic Conditions. Front Psychol. 2020 Aug 5;11:1792.
17Lanska DJ. JL Corning and vagal nerve stimulation for seizures in the 1880s. Neurology. 2002 Feb 12;58(3):452-9.
18Johnson RL, Wilson CG. A review of vagus nerve stimulation as a therapeutic intervention. J Inflamm Res. 2018 May 16;11:203-213.
19De Ferrari GM, Stolen C, Tuinenburg AE, Wright DJ, Brugada J, Butter C, Klein H, Neuzil P, Botman C, Castel MA, D'Onofrio A. Long-term vagal stimulation for heart failure: Eighteen month results from the NEural Cardiac TherApy foR Heart Failure (NECTAR-HF) trial. International journal of cardiology. 2017 Oct 1;244:229-34.
20Lampros M, Vlachos N, Zigouris A, Voulgaris S, Alexiou GA. Transcutaneous Vagus Nerve Stimulation (t-VNS) and epilepsy: A systematic review of the literature. Seizure. 2021 May 24;91:40-48.
21Lange G, Janal MN, Maniker A, FitzGibbons J, Fobler M, Cook D, Natelson BH. Safety and efficacy of vagus nerve stimulation in fibromyalgia: a phase I/II proof of concept trial. Pain Medicine. 2011 Sep 1;12(9):1406-13.
22Bottomley JM, LeReun C, Diamantopoulos A, Mitchell S, Gaynes BN. Vagus nerve stimulation (VNS) therapy in patients with treatment resistant depression: A systematic review and meta-analysis. Comprehensive psychiatry. 2020 Apr 1;98:152156.
23Goadsby PJ, Grosberg BM, Mauskop A, Cady R, Simmons KA. Effect of noninvasive vagus nerve stimulation on acute migraine: an open-label pilot study. Cephalalgia. 2014 Oct;34(12):986-93.
24Silberstein SD, Calhoun AH, Lipton RB, Grosberg BM, Cady RK, Dorlas S, Simmons KA, Mullin C, Liebler EJ, Goadsby PJ, Saper JR. Chronic migraine headache prevention with noninvasive vagus nerve stimulation: The EVENT study. Neurology. 2016 Aug 2;87(5):529-38.
25Hakon J, Moghiseh M, Poulsen I, Øland CM, Hansen CP, Sabers A. Transcutaneous vagus nerve stimulation in patients with severe traumatic brain injury: a feasibility trial. Neuromodulation: Technology at the Neural Interface. 2020 Aug;23(6):859-64.
26Li S, Qi D, Li JN, Deng XY, Wang DX. Vagus nerve stimulation enhances the cholinergic anti-inflammatory pathway to reduce lung injury in acute respiratory distress syndrome via STAT3. Cell Death Discovery. 2021 Mar 29;7(1):1-9.
27Yin J, Ji F, Gharibani P, Chen JD. Vagal nerve stimulation for glycemic control in a rodent model of type 2 diabetes. Obesity surgery. 2019 Sep;29(9):2869-77.
28Drewes AM, Brock C, Rasmussen SE, Møller HJ, Brock B, Deleuran BW, Farmer AD, Pfeiffer-Jensen M. Short-term transcutaneous non-invasive vagus nerve stimulation may reduce disease activity and pro-inflammatory cytokines in rheumatoid arthritis: results of a pilot study. Scandinavian journal of rheumatology. 2021 Jan 2;50(1):20-7.
29Genovese MC, Gaylis N, Sikes D, Kivitz A, Horowitz DM, Peterfy C, Levine Y, Chernoff D. LB0009 First-in-human study of novel implanted vagus nerve stimulation device to treat rheumatoid arthritis. 2019, June 27;78:264.
30Aranow C, Atish-Fregoso Y, Lesser M, Mackay M, Anderson E, Chavan S, Zanos TP, Datta-Chaudhuri T, Bouton C, Tracey KJ, Diamond B. Transcutaneous auricular vagus nerve stimulation reduces pain and fatigue in patients with systemic lupus erythematosus: a randomised, double-blind, sham-controlled pilot trial. Annals of the Rheumatic Diseases. 2021 Feb 1;80(2):203-8.
31Ramkissoon CM, Güemes A, Vehi J. Overview of therapeutic applications of non-invasive vagus nerve stimulation: a motivation for novel treatments for systemic lupus erythematosus. Bioelectronic Medicine. 2021 Dec;7(1):1-1.
32Sinniger V, Pellissier S, Fauvelle F, Trocmé C, Hoffmann D, Vercueil L, Cracowski JL, David O, Bonaz B. A 12‐month pilot study outcomes of vagus nerve stimulation in Crohn's disease. Neurogastroenterology & Motility. 2020 Oct;32(10):e13911.
33Bonaz B, Sinniger V, Hoffmann D, Clarencon D, Mathieu N, Dantzer C, Vercueil L, Picq C, Trocmé C, Faure P, Cracowski JL. Chronic vagus nerve stimulation in Crohn's disease: a 6‐month follow‐up pilot study. Neurogastroenterology & Motility. 2016 Jun;28(6):948-53.
34Hamasaki H. Effects of Diaphragmatic Breathing on Health: A Narrative Review. Medicines. 2020 Oct;7(10):65.
35Ma X, Yue ZQ, Gong ZQ, Zhang H, Duan NY, Shi YT, Wei GX, Li YF. The effect of diaphragmatic breathing on attention, negative affect and stress in healthy adults. Frontiers in psychology. 2017 Jun 6;8:874.
36Chang RB, Strochlic DE, Williams EK, Umans BD, Liberles SD. Vagal sensory neuron subtypes that differentially control breathing. Cell. 2015 Apr 23;161(3):622-33.
37Gerritsen RJS, Band GPH. Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity. Front Hum Neurosci. 2018 Oct 9;12:397.
38Russo MA, Santarelli DM, O’Rourke D. The physiological effects of slow breathing in the healthy human. Breathe. 2017 Dec 1;13(4):298-309.
39Mason H, Vandoni M, Debarbieri G, Codrons E, Ugargol V, Bernardi L. Cardiovascular and respiratory effect of yogic slow breathing in the yoga beginner: what is the best approach? Evid Based Complement Alternat Med. 2013;2013:743504.
40Pramanik T, Sharma HO, Mishra S, Mishra A, Prajapati R, Singh S. Immediate effect of slow pace bhastrika pranayama on blood pressure and heart rate. J Altern Complement Med 2009;15:293–5.
41Wang SZ, Li S, Xu XY, Lin GP, Shao L, Zhao Y, Wang TH. Effect of slow abdominal breathing combined with biofeedback on blood pressure and heart rate variability in prehypertension. The Journal of Alternative and Complementary Medicine. 2010 Oct 1;16(10):1039-45.
42Vickhoff B, Malmgren H, Aström R, Nyberg G, Ekström SR, Engwall M, Snygg J, Nilsson M, Jörnsten R. Music structure determines heart rate variability of singers. Front Psychol. 2013 Jul 9;4:334. doi: 10.3389/fpsyg.2013.00334. Erratum in: Front Psychol. 2013 Sep 05;4:599.
43Gurjar AA, Ladhake SA, Thakare AP. Analysis of acoustic of “OM” chant to study it's effect on nervous system. Int J Comput Sci Netw Secur. 2009 Jan;9:363-7.
44Kalyani BG, Venkatasubramanian G, Arasappa R, Rao NP, Kalmady SV, Behere RV, Rao H, Vasudev MK, Gangadhar BN. Neurohemodynamic correlates of 'OM' chanting: A pilot functional magnetic resonance imaging study. Int J Yoga. 2011 Jan;4(1):3-6.
45Arora J, Dubey N. Immediate benefits of “Om” chanting on blood pressure and pulse rate in uncomplicated moderate hypertensive subjects. National Journal of Physiology, Pharmacy and Pharmacology. 2018;8(8):1162-5.
46Alarmelu N, Archana R. Alleviation of Menopausal Symptoms by Om Chanting during Covid-19 pandemic Lockdown. Annals of Tropical Medicine and Public Health. 2020 Dec;23:232-369.
47Mooventhan A, Khode V. Effect of Bhramari pranayama and OM chanting on pulmonary function in healthy individuals: A prospective randomized control trial. International journal of yoga. 2014 Jul;7(2):104.
48Rankhambe HB, Pande S. Effect of “Om” chanting on anxiety in bus drivers. National Journal of Physiology, Pharmacy and Pharmacology. 2020;10(12):1138-41.
49Amin, A, Kumar, S.S., Rajagopalan, A., Rajan, S., Mishra, S., Reddy, UK., Mukkadan, JK. Beneficial effects of OM chanting on depression, anxiety, stress and cognition in elderly women with hypertension. Indian Journal of Clinical Anatomy and Physiology. 2016 Jul;3(3):253-5.
50Gerritsen RJ, Band GP. Breath of life: the respiratory vagal stimulation model of contemplative activity. Frontiers in human neuroscience. 2018 Oct 9;12:397.
51Keller J, Ruthruff E, Keller P. Mindfulness and divergent thinking: The value of heart rate variability as an objective manipulation check. 2017;5(3):95-104.
52Adler-Neal AL, Waugh CE, Garland EL, Shaltout HA, Diz DI, Zeidan F. The role of heart rate variability in mindfulness-based pain relief. The journal of pain. 2020 Mar 1;21(3-4):306-23.
53Wahbeh H, Goodrich E, Goy E, Oken BS. Mechanistic Pathways of Mindfulness Meditation in Combat Veterans With Posttraumatic Stress Disorder: Mechanistic Pathways of Mindfulness Meditation. Journal of clinical psychology. 2016;72(4):365–83.
54Delgado-Pastor LC, Perakakis P, Subramanya P, Telles S, Vila J. Mindfulness (vipassana) meditation: Effects on P3b event-related potential and heart rate variability. International Journal of Psychophysiology. 2013;90(2):207–14.
55Malik M, Bigger J. T Jr, Camm AJ, Breithardt G, Cerutti S, Cohen RJ, et al. Heart rate variability. standards of measurement, physiological interpretation, and clinical use. European Heart Journal. 1996;17(3):354–81.
56Shaffer F, McCraty R, Zerr CL. A healthy heart is not a metronome: an integrative review of the heart's anatomy and heart rate variability. Front Psychol. 2014;5:1040. 57.
57Saeed SA, Cunningham K, Bloch RM. Depression and anxiety disorders: benefits of exercise, yoga, and meditation. American family physician. 2019 May 15;99(10):620-7.
58Breedvelt JJ, Amanvermez Y, Harrer M, Karyotaki E, Gilbody S, Bockting CL, Cuijpers P, Ebert DD. The effects of meditation, yoga, and mindfulness on depression, anxiety, and stress in tertiary education students: a meta-analysis. Frontiers in psychiatry. 2019 Apr 24;10:193.
59Gautam S, Tolahunase M, Kumar U, Dada R. Impact of yoga based mind-body intervention on systemic inflammatory markers and co-morbid depression in active Rheumatoid arthritis patients: A randomized controlled trial. Restorative neurology and neuroscience. 2019 Jan 1;37(1):41-59.
60Park CL, Finkelstein‐Fox L, Sacco SJ, Braun TD, Lazar S. How does yoga reduce stress? A clinical trial testing psychological mechanisms. Stress and Health. 2021 Feb;37(1):116-26.
61Marshall M, McClanahan M, McArthur Warren S, Rogers R, Ballmann C. A comparison of the acute effects of different forms of yoga on physiological and psychological stress: a pilot study. International journal of environmental research and public health. 2020 Jan;17(17):6090.
62Varambally S, George S, Gangadhar BN. Yoga for psychiatric disorders: from fad to evidence-based intervention?. The British Journal of Psychiatry. 2020 Jun;216(6):291-3.
63Tyagi A, Cohen M. Yoga and heart rate variability: A comprehensive review of the literature. Int J Yoga. 2016 Jul-Dec;9(2):97-113.
64McGeoch PD, Rouw R. How everyday sounds can trigger strong emotions: ASMR, misophonia and the feeling of wellbeing. BioEssays. 2020 Dec;42(12):2000099.
65Idayati R, Sufani L, Syahputra DA. Effect of watching autonomous sensory meridian response (AMR) video to heart rate, blood pressure and respiratory rate in students of Architectural Engineering, Universitas Syiah Kuala, Banda Aceh, Indonesia. Bali Medical Journal. 2021 Aug;10(2):733-36.
66Hayashi K, Kawachi I, Ohira T, Kondo K, Shirai K, Kondo N. Laughter and subjective health among community-dwelling older people in Japan: Cross-sectional analysis of the Japan gerontological evaluation study cohort data. The Journal of nervous and mental disease. 2015 Dec;203(12):934.
67Dolgoff-Kaspar R, Baldwin A, Johnson MS, Edling N, Sethi GK. Effect of laughter yoga on mood and heart rate variability in patients awaiting organ transplantation: a pilot study. Altern Ther Health Med. 2012 Sep-Oct;18(5):61-6.
68Smyth MD, Tubbs RS, Bebin EM, Grabb PA, Blount JP. Complications of chronic vagus nerve stimulation for epilepsy in children. J Neurosurg. 2003 Sep;99(3):500-3.
69Holt-Lunstad J, Smith TB, Baker M, Harris T, Stephenson D. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspectives on psychological science. 2015 Mar;10(2):227-37.
70Hemingway H, Shipley M, Brunner E, Britton A, Malik M, Marmot M. Does autonomic function link social position to coronary risk? The Whitehall II study. Circulation. 2005 Jun 14;111(23):3071-7.
71Kok BE, Coffey KA, Cohn MA, Catalino LI, Vacharkulksemsuk T, Algoe SB, Brantley M, Fredrickson BL. How positive emotions build physical health: Perceived positive social connections account for the upward spiral between positive emotions and vagal tone. Psychological science. 2013 Jul;24(7):1123-32.
72Xia N, Li H. Loneliness, social isolation, and cardiovascular health. Antioxidants & redox signaling. 2018 Mar 20;28(9):837-51.
73Stanley J, Peake JM, Buchheit M. Cardiac parasympathetic reactivation following exercise: implications for training prescription. Sports medicine. 2013 Dec;43(12):1259-77.
74Michael S, Graham KS, Davis GM. Cardiac autonomic responses during exercise and post-exercise recovery using heart rate variability and systolic time intervals—a review. Frontiers in physiology. 2017 May 29;8:301.
75Lujan HL, DiCarlo SE. Physical activity, by enhancing parasympathetic tone and activating the cholinergic anti-inflammatory pathway, is a therapeutic strategy to restrain chronic inflammation and prevent many chronic diseases. Medical hypotheses. 2013 May 1;80(5):548-52.
76Middleton N, De Vito G. Cardiovascular autonomic control in endurance‐trained and sedentary young women. Clinical physiology and functional imaging. 2005 Mar;25(2):83-9.
77Melanson EL, Freedson PS. The effect of endurance training on resting heart rate variability in sedentary adult males. European journal of applied physiology. 2001 Sep;85(5):442-9.
78Farinatti P, Neto SR, Dias I, Cunha FA, Bouskela E, Kraemer-Aguiar LG. Short-term resistance training attenuates cardiac autonomic dysfunction in obese adolescents. Pediatric exercise science. 2016 Aug 1;28(3):374-80.
79Ricci-Vitor AL, Bonfim R, Fosco LC, Bertolini GN, Ramos EM, Ramos D, Pastre CM, Godoy M, Vanderlei LC. Influence of the resistance training on heart rate variability, functional capacity and muscle strength in the chronic obstructive pulmonary disease. European journal of physical and rehabilitation medicine. 2013 May 23;49(6):793-801.
80Caruso FR, Arena R, Phillips SA, Bonjorno Jr JC, Mendes RG, Arakelian VM, Bassi D, Nogi C, Borghi-Silva A. Resistance exercise training improves heart rate variability and muscle performance: a randomized controlled trial in coronary artery disease patients. Eur J Phys Rehabil Med. 2015 Jun 1;51(3):281-9.
81Bravo JA, Forsythe P, Chew MV, Escaravage E, Savignac HM, Dinan TG, Bienenstock J, Cryan JF. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. Proc Natl Acad Sci U S A. 2011 Sep 20;108(38):16050-5.
82Bercik P, Park AJ, Sinclair D, Khoshdel A, Lu J, Huang X, Deng Y, Blennerhassett PA, Fahnestock M, Moine D, Berger B. The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut–brain communication. Neurogastroenterology & Motility. 2011 Dec;23(12):1132-9.
83Takada M, Nishida K, Kataoka‐Kato A, Gondo Y, Ishikawa H, Suda K, Kawai M, Hoshi R, Watanabe O, Igarashi T, Kuwano Y. Probiotic Lactobacillus casei strain Shirota relieves stress‐associated symptoms by modulating the gut–brain interaction in human and animal models. Neurogastroenterology & Motility. 2016 Jul;28(7):1027-36.
84Baumann C, Rakowski U, Buchhorn R. Omega-3 fatty acid supplementation improves heart rate variability in obese children. International journal of pediatrics. 2018 Feb 26;2018: 8789604.
85Valera B, Suhas E, Counil E, Poirier P, Dewailly E. Influence of polyunsaturated fatty acids on blood pressure, resting heart rate and heart rate variability among French Polynesians. Journal of the American College of Nutrition. 2014 Jul 4;33(4):288-96.
86Christensen JH. Omega-3 polyunsaturated Fatty acids and heart rate variability. Front Physiol. 2011 Nov 16;2:84.
87Buchhorn R, Koenig J, Jarczok MN, Eichholz H, Willaschek C, Thayer JF, Kaess M. A case series on the potential effect of omega-3-fatty acid supplementation on 24-h heart rate variability and its circadian variation in children with attention deficit (hyperactivity) disorder. ADHD Attention Deficit and Hyperactivity Disorders. 2018 Jun;10(2):135-9.
88Mozaffarian D, Stein PK, Prineas RJ, Siscovick DS. Dietary fish and ω-3 fatty acid consumption and heart rate variability in US adults. Circulation. 2008 Mar 4;117(9):1130-7.
89Mager DE, Wan R, Brown M, Cheng A, Wareski P, Abernethy DR, Mattson MP. Caloric restriction and intermittent fasting alter spectral measures of heart rate and blood pressure variability in rats. FASEB J. 2006 Apr;20(6):631-7.
90Felber Dietrich D, Schindler C, Schwartz J, Barthélémy JC, Tschopp JM, Roche F, von Eckardstein A, Brändli O, Leuenberger P, Gold DR, Gaspoz JM. Heart rate variability in an ageing population and its association with lifestyle and cardiovascular risk factors: results of the SAPALDIA study. Europace. 2006 Jul 1;8(7):521-9.
91De Jonge L, Moreira EA, Martin CK, Ravussin E, Pennington CALERIE Team. Impact of 6‐month caloric restriction on autonomic nervous system activity in healthy, overweight, individuals. Obesity. 2010 Feb;18(2):414-6.
92Mäkinen TM, Mäntysaari M, Pääkkönen T, Jokelainen J, Palinkas LA, Hassi J, Leppäluoto J, Tahvanainen K, Rintamäki H. Autonomic nervous function during whole-body cold exposure before and after cold acclimation. Aviat Space Environ Med. 2008 Sep;79(9):875-82.
93Al Haddad H, Laursen PB, Chollet D, Lemaitre F, Ahmaidi S, Buchheit M. Effect of cold or thermoneutral water immersion on post-exercise heart rate recovery and heart rate variability indices. Autonomic Neuroscience. 2010 Aug 25;156(1-2):111-6.
94Al Haddad H, Laursen PB, Ahmaidi S, Buchheit M. Influence of cold water face immersion on post-exercise parasympathetic reactivation. European journal of applied physiology. 2010 Feb;108(3):599-606.
95Damapong P, Kanchanakhan N, Eungpinichpong W, Putthapitak P, Damapong P. A randomized controlled trial on the effectiveness of court-type traditional Thai massage versus amitriptyline in patients with chronic tension-type headache. Evidence-based complementary and alternative medicine. 2015 Jan 1;2015: 930175.
96Buttagat V, Eungpinichpong W, Chatchawan U, Kharmwan S. The immediate effects of traditional Thai massage on heart rate variability and stress-related parameters in patients with back pain associated with myofascial trigger points. Journal of bodywork and movement therapies. 2011 Jan 1;15(1):15-23.
97Fazeli MS, Pourrahmat MM, Liu M, Guan L, Collet JP. The effect of head massage on the regulation of the cardiac autonomic nervous system: a pilot randomized crossover trial. The Journal of Alternative and Complementary Medicine. 2016 Jan 1;22(1):75-80.
98Lu WA, Chen GY, Kuo CD. Foot reflexology can increase vagal modulation, decrease sympathetic modulation, and lower blood pressure in healthy subjects and patients with coronary artery disease. Alternative therapies in health and medicine. 2011 Jul 1;17(4):8.
99Chan YC, Wang TJ, Chang CC, Chen LC, Chu HY, Lin SP, Chang ST. Short-term effects of self-massage combined with home exercise on pain, daily activity, and autonomic function in patients with myofascial pain dysfunction syndrome. Journal of physical therapy science. 2015;27(1):217-21.
100Field T, Diego M, Hernandez-Reif M. Potential underlying mechanisms for greater weight gain in massaged preterm infants. Infant Behavior and Development. 2011 Jun 1;34(3):383-9.