A Meta-analysis on Resting State High-frequency Heart Rate Variability in Bulimia Nervosa

Update: factors influencing heart rate variability-a narrative review

Objective

Heart rate variability (HRV) is an important non-invasive marker for the assessment of an organism's autonomic physiological regulatory pathways. Lower HRV has been shown to correlate with increased mortality. HRV is influenced by various factors or diseases. The aim of this narrative review is to describe the current state of knowledge on factors influencing HRV and their significance for interpretation.

Methods

The narrative review only included reviews, meta-analyses, and cohort studies which were published until 2021. HRV confounders were grouped into four categories (non-influenceable physiological factors, diseases, influenceable lifestyle factors and external factors).

Results

The review found that HRV was decreased not only in non-influenceable physiological factors (e.g., age, gender, ethnicity) but also in connection with various number of acute and chronic diseases (e.g., psychiatric diseases, myocardial infarction, heart failure), influenceable lifestyle factors (e.g., alcohol abuse, overweight, physical activity), and external factors (e.g., heat, noise, shift work, harmful- and hazardous substances).

Conclusion

In order to improve the quality of HRV studies and to ensure accurate interpretation, it is recommended that confounders be taken into account in future diagnostic measurements or measurements in the workplace (e.g., as part of health promotion measures) in order to counteract data bias.

Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science

This updated guideline replaces the "Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science" first published in 2014. Based on the older version of the guideline, the authors have reviewed and evaluated the findings on the use of heart rate (HR) and heart rate variability (HRV) that have been published in the meantime and incorporated them into a new version of this guideline.This guideline was developed for application in clinical practice and research purposes in the fields of occupational medicine and occupational science to complement evaluation procedures with respect to exposure and risk assessment at the workplace by the use of objective physiological workload indicators. In addition, HRV is also suitable for assessing the state of health and for monitoring the progress of illnesses and preventive medical measures. It gives an overview of factors influencing the regulation of the HR and HRV at rest and during work. It further illustrates methods for measuring and analyzing these parameters under standardized laboratory and real workload conditions, areas of application as well as the quality control procedures to be followed during the recording and evaluation of HR and HRV.

Complementary and Integrative Medicine and Eating Disorders in Youth: Traditional Yoga, Virtual Reality, Light Therapy, Neurofeedback, Acupuncture, Energy Psychology Techniques, Art Therapies, and Spirituality

Eating disorders (EDs) are a non-heterogeneous group of illnesses with significant physical and mental comorbidity and mortality associated with maladaptive coping. With the exception of lisdexamfetamine (Vyvanse) for binge eating disorder, no medications have been effective for the core symptoms of ED. ED requires a multimodal approach. Complementary and integrative medicine (CIM) can be helpful as an adjunct. The most promising CIM interventions are traditional yoga, virtual reality, eye movement desensitization and reprocessing, Music Therapy, and biofeedback/neurofeedback.

Meta-Analysis and Systematic Review of Resting-State High-Frequency Heart Rate Variability in Binge-Eating Disorder

Abstract. Binge-eating disorder (BED) is associated with a greater risk for cardiac problems and co-occurring health conditions. Resting-state measures of high-frequency heart rate variability (HF-HRV), which is a physiological proxy of self-regulatory neural functioning, may aid understanding of health risks. We systematically reviewed and meta-analyzed the literature on HF-HRV in individuals with BED and without BED. Six studies were reviewed in the qualitative synthesis, and five studies assessing HRV in individuals with BED ( n = 153) and without BED ( n = 124) were included in the meta-analysis. A non-significant effect size (Hedges’ g = .08, SE = 0.36, 95% CI [−0.62, 0.78]; z = 0.23, p = .82) was found, suggesting no difference in HF-HRV between groups. Age, BMI, and BMI-matched control status were not significant covariates. Synthesizing the five studies with available data, we found no difference in resting-state HF-HRV between individuals with and without BED. There was high heterogeneity in the sample, suggesting potential moderators. We discuss potential mechanisms, methodological and demographic confounds, and future directions for study.

Negative mood induction effects on problem-solving task in women with eating disorders: a multi-method examination

BACKGROUND

The effects of negative affect on problem-solving and its psychophysiological correlates are poorly understood in eating disorder populations.

METHODS

This study examined respiratory sinus arrhythmia (RSA) and skin conductance responses of women with Binge Eating Disorder (BED: n = 56), Anorexia Nervosa (AN: n = 12), Bulimia Nervosa (BN: n = 32), and 24 healthy controls (HCs) at baseline, and then during: a negative mood induction task, an adapted Means Ends Problem-Solving (MEPS) task, and recovery. The MEPS task included four interpersonal scenarios: (1) binge-eating as a solution to stress, (2) job loss, (3) rejection by friends, and (4) by a significant other.

RESULTS

We found that individuals with eating disorders reported less positive mood than HCs and individuals with BN and BED reported more negative mood and greater urges to binge than HCs. After a negative mood induction, women with BED provided significantly less effective problem-solving strategies compared to HCs and women with BN for the binge-eating MEPS scenario. Relative to baseline and the negative mood induction, all participants exhibited significantly higher skin conductance measures throughout the MEPS scenarios and recovery. BED showed significantly lower respiratory sinus arrhythmia (RSA) levels than individuals with BN and HCs throughout the protocol.

CONCLUSIONS

The multimethod findings suggest individuals with BED are likely to have disorder-specific problem-solving difficulties after a negative mood induction.

The peril and promise of sensitivity in eating disorders

Differential susceptibility, a reconceptualization of the diathesis-stress model of psychopathology, describes gene-environment interactions that reflect individual differences in responsiveness to environmental influences, both detrimental and beneficial. This model has been described metaphorically by the classification of orchids, which thrive under optimal care but wither under adverse conditions, and dandelions, which weather broad environmental circumstances but are less responsive to careful cultivation. Etiological research in the field of eating disorders has largely focused on the identification of specific behavioral phenotypes, temperamental traits, genotypes and neurobiological processes that confer risk. In this article, we propose that these putative vulnerability factors represent phenotypes and endophenotypes of a genetic predisposition towards environmental sensitivity. We assert that this sensitivity not only transmits eating disorder risk but also confers resilience, depending on the circumstances. In particular, we propose that differential susceptibility can be used as a framework to organize disparate temperamental and neurobiological findings and their complex interplay with various developmental, environmental and sociocultural influences to increase eating disorder risk and treatment responsiveness. Finally, we assert that viewed through the lens of differential susceptibility, sensitivity can be leveraged to refine our interventions and develop novel treatment and prevention strategies to support favorable outcomes for individuals with eating disorders.

Parsing inter- and intra-individual variability in key nervous system mechanisms of stress responsivity and across functional domains

Exposure to stressful events is omnipresent in modern human life, yet people show considerable heterogeneity in the impact of stress exposure(s) on their functionality and overall health. Encounter with stressor(s) is counteracted by an intricate repertoire of nervous-system responses. This narrative review starts with a brief summary of the vast evidence that supports heart rate variability, cortisol secretion, and large-scale cortical network interactions as kay physiological, endocrinological, and neural mechanisms of stress responsivity, respectively. The second section highlights potential sources for inter-individual variability in these mechanisms, by focusing on biological, environmental, social, habitual, and psychological factors that may influence stress responsivity patterns and thus contribute to heterogeneity in the impact of stress exposure on functionality and health. The third section introduces intra-individually variability in stress responsivity across functional domains as a novel putative source for heterogeneity in the impact of stress exposure. Challenges and future directions are further discussed. Parsing inter- and intra-individual variability in nervous-system mechanisms of stress responsivity and across functional domains is critical towards potential clinical translation.

Multi-method assessment of palatable food exposure in women with and without eating disorders

OBJECTIVE

Eating disorders (EDs) are characterized by dysregulated responses to palatable food. Using a multi-method approach, this study examined responses to palatable food exposure and subsequent ad libitum eating in women with binge-eating disorder (BED: n = 64), anorexia nervosa (AN: n = 16), and bulimia nervosa (BN: n = 35) and 26 healthy controls (HCs).

METHOD

Participants were exposed to palatable food followed by an ad libitum eating opportunity. Affective and psychophysiological responses were measured before and during the task.

RESULTS

Participants with EDs reported greater negative affect, particularly fear, following the food cue exposure, whereas HCs reported no change. BN and BED groups reported greater urge to binge after the food cue exposure, whereas AN and HC groups reported no change. Respiratory sinus arrhythmia levels, skin conductance and tonic skin conductance levels increased during food exposure for all groups. Across baseline and during the food exposure, the BED group had lower respiratory sinus arrhythmia levels relative to the BN and HC groups. The BED group consumed significantly more palatable food than the AN group.

CONCLUSIONS

'Palatable' food stimuli elicited more negative affect, particularly fear, in individuals with EDs; and this, rather than psychophysiological responses, distinguishes individuals with EDs from those without.

Resting state heart rate variability in clinical and subthreshold disordered eating: A meta-analysis

OBJECTIVE

Research has demonstrated mixed results regarding the direction of the association between vagal activation and disordered eating. The current meta-analysis examined studies testing the link between resting-state heart rate variability indices of vagal activation (vmHRV), and both clinical and subthreshold disordered eating.

METHOD

A systematic search of the literature resulted in the inclusion of studies that were correlational (associations between HRV and disordered eating symptoms) and that examined group differences (e.g., control group vs. disordered eating group), for a total of 36 samples.

RESULTS

Findings indicated a small but reliable association of vmHRV with disordered eating, r = 0.12, indicating greater vagal activation in individuals with disordered eating compared to those with little or no disordered eating behavior. Moderation analyses identified predictors of the vmHRV/disordered eating association. Bulimia nervosa was found to have a large, positive effect size with vmHRV, r = 0.60, which was significantly greater than all other types of disordered eating, Q _T = 10.74, p = .047. Compared to subthreshold disordered eating, clinical eating disorders demonstrated significant, persistent increased vagal activation with a medium, reliable effect size, r = 25, Q_T = 3.94, p = .045.

CONCLUSION

These insights contribute to an improved understanding of the pathophysiology in disordered eating.

The relationship between sleep and autonomic health

Objective: To examine the relationship between sleep and resting autonomic nervous system (ANS) functioning in college students. Participants: Participants were 141 undergraduate students (52 males) recruited from a large southeastern university during September-October 2017. Methods: Participants completed self-report inventories (demographic and sleep characteristics). Resting state skin conductance (SC) and heart rate variability (HRV) were measured in a laboratory setting for ANS functioning. Results: SC was positively associated with sleep quality (p = 0.027), sleep latency (p = 0.040), and use of sleep medication (p < 0.001). Analyses yielded a negative association between the standard deviation of the normal-normal interval of heart beats (SDNN) and the self-reported amount of time to fall asleep each night (p = 0.041). Sleep efficiency was negatively correlated with low frequency HRV (p = 0.002). Conclusions: Sleep components are associated with resting ANS activity, and targeted interventions focused on improved ANS functioning may benefit sleep quality in college students.

Moving beyond self-report data collection in the natural environment: A review of the past and future directions for ambulatory assessment in eating disorders

OBJECTIVE

In recent years, ecological momentary assessment (EMA) has been used to repeatedly assess eating disorder (ED) symptoms in naturalistic settings, which has allowed for increased understanding of temporal processes that potentiate ED behaviors. However, there remain notable limitations of self-report EMA, and with the rapid proliferation of technology there are ever-increasing possibilities to improve ambulatory assessment methods to further the understanding and treatment of EDs. Therefore, the purpose of this review was to (a) systematically review the studies in EDs that have utilized ambulatory assessment methods other than self-report, and (b) provide directions for future research and clinical applications.

METHOD

A systematic literature search of electronic databases was conducted, and data regarding study characteristics and methodological quality were extracted.

RESULTS

The search identified 17 studies that used ambulatory assessment methods to gather objective data, and focused primarily on autonomic functioning, physical activity, and cognitive processes in ED and control groups.

DISCUSSION

Together the literature demonstrates the promise of using a range of ecologically valid ambulatory assessment approaches in EDs, though there remains limited research that has utilized methods other than self-report (e.g., wearable sensors), particularly in recent years. Going forward, there are several technology-enhanced momentary assessment methods that have potential to improve the understanding and treatment of EDs.

Heart-rate variability: a biomarker to study the influence of nutrition on physiological and psychological health?

As the influence of diet on health may take place over a period of decades, there is a need for biomarkers that help to identify those aspects of nutrition that have either a positive or a negative influence. The evidence is considered that heart-rate variability (HRV) (the time differences between one beat and the next) can be used to indicate the potential health benefits of food items. Reduced HRV is associated with the development of numerous conditions for example, diabetes, cardiovascular disease, inflammation, obesity and psychiatric disorders. Although more systematic research is required, various aspects of diet have been shown to benefit HRV acutely and in the longer term. Examples include a Mediterranean diet, omega-3 fatty acids, B-vitamins, probiotics, polyphenols and weight loss. Aspects of diet that are viewed as undesirable, for example high intakes of saturated or trans-fat and high glycaemic carbohydrates, have been found to reduce HRV. It is argued that the consistent relationship between HRV, health and morbidity supports the view that HRV has the potential to become a widely used biomarker when considering the influence of diet on mental and physical health.

Distress tolerance across self-report, behavioral and psychophysiological domains in women with eating disorders, and healthy controls

BACKGROUND AND OBJECTIVES

The tendency to engage in impulsive behaviors when distressed is linked to disordered eating. The current study comprehensively examines emotional responses to a distress tolerance task by utilizing self-report, psychophysiological measures (respiratory sinus arrhythmia [RSA], skin conductance responses [SCRs] and tonic skin conductance levels [SCLs]), and behavioral measures (i.e., termination of task, latency to quit task).

METHODS

26 healthy controls (HCs) and a sample of treatment-seeking women with Bulimia Nervosa (BN), Binge Eating Disorder (BED) and Anorexia Nervosa (AN) (N = 106) completed the Paced Auditory Serial Addition Task- Computerized (PASAT-C). Psychophysiological measurements were collected during baseline, PASAT-C, and recovery, then averaged for each time period. Self-reported emotions were collected at baseline, post-PASAT-C and post-recovery.

RESULTS

Overall, we found an effect of Time, with all participants reporting greater negative emotions, less happiness, lower RSA, more SCRs and higher tonic SCLs after completion of the PASAT-C relative to baseline. There were no differences in PASAT-C performance between groups. There was an effect of Group for negative emotions, with women with BN, BED and AN reporting overall higher levels of negative emotions relative to HCs. Furthermore, we found an effect of Group for greater urges to binge eat and lower RSA values among BED, relative to individuals with BN, AN and HCs.

LIMITATIONS

This study is cross-sectional and lacked an overweight healthy control group.

CONCLUSION

During the PASAT-C, individuals with eating disorders (EDs) compared to HCs report higher levels of negative emotions, despite similar physiological and behavioral manifestations of distress.

Vagal Tank Theory: The Three Rs of Cardiac Vagal Control Functioning - Resting, Reactivity, and Recovery

The aim of this paper is to set the stage for the vagal tank theory, showcasing a functional resource account for self-regulation. The vagal tank theory, building on neurophysiological, cognitive and social psychology approaches, will introduce a physiological indicator for self-regulation that has mainly been ignored from cognitive and social psychology, cardiac vagal control (also referred to as cardiac vagal activity). Cardiac vagal control reflects the contribution of the vagus nerve, the main nerve of the parasympathetic nervous system, to cardiac regulation. We propose cardiac vagal control to be an indicator of how efficiently self-regulatory resources are mobilized and used. Three systematic levels of cardiac vagal control analysis are suggested: resting, reactivity, and recovery. Based on this physiological indicator we derive the metaphor of the vagal tank, which can get depleted and replenished. Overall, the vagal tank theory will enable to integrate previous findings from different disciplines and to stimulate new research questions, predictions, and designs regarding self-regulation.

Heart rate variability in individuals with Down syndrome - A systematic review and meta-analysis

INTRODUCTION

Down syndrome (DS) results in many changes, including dysfunction in cardiac autonomic modulation. Heart rate variability (HRV) analysis evaluates the autonomic function and it is a predictor of adverse cardiovascular events.

OBJECTIVE

To present results of a systematic review and a meta-analysis about heart rate variability in individuals with DS.

METHOD

A systematic review was performed on PubMed, PubMed Central and Web of science databases. We included articles that exhibited all the terms: "Down Syndrome", "heart rate variability", "autonomic nervous system", "autonomic dysfunction" and "cardiac autonomic modulation". We conducted the meta-analysis to compare "DS" to "controls" during rest. Random effects models were used, as were appropriate tests for heterogeneity.

RESULTS

From 271 studies, 13 were included in our review. These are conducted with volunteers from a wide age range, of either gender, and not taking medications. Meta-analysis displayed that there were no significant differences between the groups at rest, except the RMSSD, which revealed a significant (Z = -2.80, p = 0.005) main effect (Hedge's g = -0.55, 95% CI [-0.93; -0.16]), indicating difference in individuals with DS compared with controls.

CONCLUSION

There is autonomic dysfunction in individuals with DS, which may or may not be expressed at rest, but it is usually demonstrated in an autonomic task. Meta-analysis specified that there was no significant alteration between DS and the controls during rest, except RMSSD index which was lower in DS than controls.

PROSPERO

CRD42017068647.

Is intuitive eating related to resting state vagal activity?

Efferent and afferent fibers of the vagus nerve are involved in regulating hunger and satiety. Vagally-mediated heart rate variability (vmHRV) reflects vagal activity. Previously no study addressed a potential association between resting state vagal activity and intuitive eating. Self-reports on intuitive eating and measures of resting state vmHRV were obtained in 39 students (16 female, mean age: 19.64±1.44years). Hierarchical multiple regression models showed that, after controlling for gender, age, and body mass index, resting vagal activity was inversely related to the Unconditional Permission to Eat subscale of the Intuitive Eating scale. Individuals with higher resting vagal activity tend to be less willing to eat desired foods and are more likely to label certain foods as forbidden. Future studies should include measures of self-regulation and eating disorder symptomatology to identify potential mediators or moderators when attempting to replicate these preliminary findings in larger samples.

Non-suicidal Self-Injury in Eating Disordered Patients: Associations with Heart Rate Variability and State-Trait Anxiety

Background: Non-suicidal self-injury (NSSI) is commonly present in individuals with eating disorders (EDs) and is often employed as a maladaptive emotion regulation strategy to avoid or abate negative emotions. One of the most prevalent negative emotions experienced by self-injurers is anxiety; however, this emotion has not been extensively studied in this population. Thus, the aim of our study was to investigate the influence of anxiety on NSSI in patients with ED from two different dimensions: state anxiety and trait anxiety.

Methods: The study comprised a total of 66 females: 12 ED patients with NSSI, 32 ED patients without a history of NSSI, and 22 healthy controls. State and trait anxiety were assessed by means of State-Trait Anxiety Inventory (STAI-S-T) and physiological data [i.e., heart rate variability (HRV)] were collected.

Results: STAI-trait scores were significantly higher in ED patients with NSSI than ED patients without NSSI. Furthermore, when conducting logistic regression analyses higher STAI-trait scores were associated with NSSI in ED patients. However, no differences in STAI-state scores and HRV were found between ED patients with and without NSSI.

Discussion: The present findings suggest that anxiety as a trait is associated with the use of maladaptive strategies (i.e., NSSI) in ED patients. These results uphold the need to target trait anxiety in ED treatment in order to prevent possible NSSI behaviors.

Obesity is associated with lack of inhibitory control and impaired heart rate variability reactivity and recovery in response to food stimuli

Recent theories compare obesity with addiction in terms of lack of inhibitory control in both clinical populations. The present study hypothesized impaired inhibition in obese patients reflected both in executive functions and reduced vagal tone (indexed by a decrease in heart rate variability; HRV) in response to food stimuli. Twenty-four inpatients with obesity (19 women) and 37 controls (24 women) underwent ECG monitoring during baseline, food stimuli viewing, and a recovery phase. Tests and questionnaires assessing inhibitory control and psychopathological dispositions were also administered. As hypothesized, patients were characterized by deficits in all the tests measuring inhibitory capacities. Results also show greater HRV reduction and impaired HRV recovery in response to food stimuli in obese patients compared to controls. The drive to eat experienced by obese patients in the absence of caloric need may rely on impairments in inhibitory and vagal functioning. Results are discussed in terms of implications for therapy.

Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research - Recommendations for Experiment Planning, Data Analysis, and Data Reporting

Psychophysiological research integrating heart rate variability (HRV) has increased during the last two decades, particularly given the fact that HRV is able to index cardiac vagal tone. Cardiac vagal tone, which represents the contribution of the parasympathetic nervous system to cardiac regulation, is acknowledged to be linked with many phenomena relevant for psychophysiological research, including self-regulation at the cognitive, emotional, social, and health levels. The ease of HRV collection and measurement coupled with the fact it is relatively affordable, non-invasive and pain free makes it widely accessible to many researchers. This ease of access should not obscure the difficulty of interpretation of HRV findings that can be easily misconstrued, however, this can be controlled to some extent through correct methodological processes. Standards of measurement were developed two decades ago by a Task Force within HRV research, and recent reviews updated several aspects of the Task Force paper. However, many methodological aspects related to HRV in psychophysiological research have to be considered if one aims to be able to draw sound conclusions, which makes it difficult to interpret findings and to compare results across laboratories. Those methodological issues have mainly been discussed in separate outlets, making difficult to get a grasp on them, and thus this paper aims to address this issue. It will help to provide psychophysiological researchers with recommendations and practical advice concerning experimental designs, data analysis, and data reporting. This will ensure that researchers starting a project with HRV and cardiac vagal tone are well informed regarding methodological considerations in order for their findings to contribute to knowledge advancement in their field.

Major depressive disorder and generalized anxiety disorder show different autonomic dysregulations revealed by heart-rate variability analysis in first-onset drug-naïve patients without comorbidity

AIM

The aim of the present study was to examine whether depression and anxiety disorder manifest different autonomic dysregulations using heart-rate variability (HRV) and heart rate (HR) measurements.

METHODS

HRV and HR were recorded both at rest and during task execution (random-number generation) in first-onset drug-naïve patients with major depressive disorder (MDD, n = 14) and generalized anxiety disorder (GAD, n = 11) as well as in healthy controls (n = 41). The patients showed no comorbidity of depression and anxiety disorder. GAD patients did not exhibit panic or phobic symptoms at the time of measurement. Following power spectrum analysis of HR trend, the high- (HF) and low-frequency (LF) components, the sum (LF + HF), and the LF/HF ratio were compared among the groups.

RESULTS

In the MDD patients, as previously reported, HF was low and the LF/HF ratio was high during the initial-rest condition, and HF was less reactive to the task. In contrast, GAD patients showed significantly high HF, although autonomic reactivity was not impaired.

CONCLUSION

The results indicate that baseline autonomic activity and its reactivity to behavioral changes are different between MDD and GAD in the early stage of illness. High parasympathetic tone in GAD may reflect responses of the parasympathetic system to anxiety. MDD is accompanied by an autonomic shift toward sympathetic activation and a reduced reactivity to task.

Non-suicidal Self-Injury in Eating Disordered Patients: Associations with Heart Rate Variability and State-Trait Anxiety

Background: Non-suicidal self-injury (NSSI) is commonly present in individuals with eating disorders (EDs) and is often employed as a maladaptive emotion regulation strategy to avoid or abate negative emotions. One of the most prevalent negative emotions experienced by self-injurers is anxiety; however, this emotion has not been extensively studied in this population. Thus, the aim of our study was to investigate the influence of anxiety on NSSI in patients with ED from two different dimensions: state anxiety and trait anxiety. Methods: The study comprised a total of 66 females: 12 ED patients with NSSI, 32 ED patients without a history of NSSI, and 22 healthy controls. State and trait anxiety were assessed by means of State-Trait Anxiety Inventory (STAI-S-T) and physiological data [i.e., heart rate variability (HRV)] were collected. Results: STAI-trait scores were significantly higher in ED patients with NSSI than ED patients without NSSI. Furthermore, when conducting logistic regression analyses higher STAI-trait scores were associated with NSSI in ED patients. However, no differences in STAI-state scores and HRV were found between ED patients with and without NSSI. Discussion: The present findings suggest that anxiety as a trait is associated with the use of maladaptive strategies (i.e., NSSI) in ED patients. These results uphold the need to target trait anxiety in ED treatment in order to prevent possible NSSI behaviors.

Statistical considerations for reporting and planning heart rate variability case-control studies

The calculation of heart rate variability (HRV) is a popular tool used to investigate differences in cardiac autonomic control between population samples. When interpreting effect sizes to quantify the magnitude of group differences, researchers typically use Cohen's guidelines of small (0.2), medium (0.5), and large (0.8) effects. However, these guidelines were originally proposed as a fallback for when the effect size distribution (ESD) was unknown. Despite the availability of effect sizes from hundreds of HRV studies, researchers still largely rely on Cohen's guidelines to interpret effect sizes and to perform power analyses to calculate required sample sizes for future research. This article describes an ESD analysis of 297 HRV effect sizes from between-group/case-control studies, revealing that the 25th, 50th, and 75th effect size percentiles correspond with effect sizes of 0.26, 0.51, and 0.88, respectively. The analyses suggest that Cohen's guidelines may underestimate the magnitude of small and large effect sizes and that HRV studies are generally underpowered. Therefore, to better reflect the observed ESD, effect sizes of 0.25, 0.5, and 0.9 should be interpreted as small, medium, and large effects (after rounding to the closest 0.05). Based on power calculations using the ESD, suggested sample sizes are also provided for planning suitably powered studies that are more likely to replicate. Researchers are encouraged to use the ESD data set or their own collected data sets in tandem with the provided analysis script to perform custom ESD and power analyses relevant to their specific research area.