Heart Rate Variability Biofeedback (HRVB) has been widely used to improve cardiovascular health and well-being. HRVB is based on breathing at an individual\'s resonance frequency, which stimulates respiratory sinus arrhythmia (RSA) and the baroreflex. There is, however, no methodological consensus on how to apply HRVB, while details about the protocol used are often not well reported. Thus, the objectives of this systematic review are to describe the different HRVB protocols and detect methodological concerns. PsycINFO, CINALH, Medline and Web of Science were searched between 2000 and April 2021. Data extraction and quality assessment were based on PRISMA guidelines. A total of 143 studies were finally included from any scientific field and any type of sample. Three protocols for HRVB were found: (i) \"Optimal RF\" (n = 37), each participant breathes at their previously detected RF; (ii) \"Individual RF\" (n = 48), each participant follows a biofeedback device that shows the optimal breathing rate based on cardiovascular data in real time, and (iii) \"Preset-pace RF\" (n = 51), all participants breathe at the same rate rate, usually 6 breaths/minute. In addition, we found several methodological differences for applying HRVB in terms of number of weeks, duration of breathing or combination of laboratory and home sessions. Remarkably, almost 2/3 of the studies did not report enough information to replicate the HRVB protocol in terms of breathing duration, inhalation/exhalation ratio, breathing control or body position. Methodological guidelines and a checklist are proposed to enhance the methodological quality of future HRVB studies and increase the information reported.

Deficits in self-regulatory control (SRC) represent a core characteristic of externalizing (EXT) symptoms (e.g., rule-breaking behavior or aggressive behaviors) in adolescents. This review aims to specify the added value of ecologically valid assessments at a micro-level when examining the associations between SRC and EXT symptoms in adolescents. This systematic review was reported according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020. The search strategy addressed the added value of (1) naturalistic assessment for the understanding of the relationship between (2) SRC and (3) EXT symptoms in (4) adolescents. We conducted comprehensive searches in bibliographic databases. An additional search was conducted in Google Scholar and supplementary studies were identified through backward and forward citation tracking. Twenty-four studies (n = 4071 adolescents) met the inclusion criteria. The methods used to assess naturalistic aspects included the experience sampling method (ecological momentary- or ambulatory assessment) and the time-course approach (i.e., real-time assessment of SRC processes referring to situations approximating real-life experience where SRC are to be engaged such as in frustrating situations). Micro-level ecological assessments, when mapping the intra-individual relationships between SRC processes and EXT symptoms over time in adolescents within their natural context (i.e., real world) of expression in real time, added a finer-grained observation alongside with a higher ecological validity. Micro-level approaches may enhance the understanding of the complex interplay between SRC and EXT symptoms in adolescence, especially in interventional studies, allowing for the acquisition of endpoints with a higher relevance for everyday functioning.

Although many studies have documented associations between insecure attachment and psychopathology, attachment may not confer risk for psychopathology independently, but rather through its interaction with emotional, social, and biological factors. Understanding the variables through which attachment may lead to psychopathology is therefore important. Within this domain of research, the role of physiological factors is poorly investigated. What are the relevant domains and why, when, or for whom do they influence mental disorders relating to attachment? The current systematic review aims to answer these questions. Results reveal that physiological indices of emotional regulation play a role in explaining and/or determining the relationship between attachment and psychopathology. Specifically: (1) combined with insecure attachment, higher skin conductance level (SCL), lower cardiac slowing, and respiratory sinus arrhythmia modulation (RSA) contribute to different psychopathological indicators and behavioral/psychological dysfunctions, although the latter predicts a contradictory pattern of findings; (2) insecure-avoidant attachment is more consistently linked with stress and emotional dysregulation when combined with RSA, while anxious attachment confers risk of depressive symptoms when combined with SCL. We concluded our discussion of the results of seven studies by outlining a plan to move the field forward. We discuss the quality of the assessment, methodological limitations, and future directions, highlighting the need to extend the research to clinical samples.

Functioning of the parasympathetic nervous system (PNS), most often indexed by respiratory sinus arrhythmia (RSA), influences the volitional, cognitively-mediated forms of self-regulation across development. However, despite its clear relevance to children\'s self-regulation, and its utility as a transdiagnostic biomarker of emotion dysregulation and psychopathology, the ontogeny of vagal tone under conditions of homeostasis across infancy and early childhood is not well understood. The current research is comprised of two complementary studies. The first aims to address this gap by conducting a systematic review of the literature which has assessed resting RSA in the first three years of life. The second study uses data from two diverse, longitudinal datasets (n = 203 and n = 370) to model change in RSA from infancy to toddlerhood. Results from a systematic review of 62 studies meeting inclusion criteria suggest that measures of resting RSA increase over time and demonstrate moderate stability across infancy, toddlerhood, and preschool ages. Results from a series of models fit to longitudinal data in study two suggest that baseline RSA is characterized by stable increases across infancy and early childhood. Moreover, although there was equivocal evidence for individual variability in trajectories of RSA, the findings suggest that the individual differences in resting RSA may become entrenched in early life based on observed significant variance in growth model intercepts. In all, the current study contributes to our understanding of the developmental trajectories of baseline RSA across infancy and early childhood and should support future research examining links between children\'s parasympathetic regulation and their adjustment in early life.

Respiratory sinus arrhythmia (RSA) reactivity is thought to indicate how adaptively one responds to stress. RSA reactivity has been examined across anxiety disorders and posttraumatic stress disorder (PTSD), to better understand the psychophysiological stress response of these disorders. The current state of the literature is mixed, and the association between RSA reactivity and PTSD/anxiety is unclear. This review examines RSA reactivity in response to laboratory stressor tasks across samples with anxiety and PTSD. Results indicated a complex literature that may suggest an association between anxiety/PTSD and RSA reactivity. There is evidence to suggest a pattern of heightened RSA withdrawal in PTSD and trait anxious samples. There was little evidence to suggest a heightened RSA withdrawal pattern in other anxiety disorders. This review also highlights methodological considerations which may allow for clearer interpretations of RSA reactivity. The current literature includes heterogeneity across stressor tasks, RSA measures, and comorbidities that complicates interpretation of results. Studies using samples with comorbid depression produce more consistent evidence of heightened RSA withdrawal in anxiety/PTSD. Future directions for understanding the contribution of these variables (i.e., stressor tasks, RSA measures, comorbid depression) and mechanisms contributing to the possible association between RSA reactivity and anxiety/PTSD are considered.

Respiratory sinus arrhythmia (RSA), an index of the parasympathetic nervous system, has recently gained attention as a physiological component of regulatory processes, social connectedness, and health. Within the context of romantic relationships, studies have operationalized and conceptualized RSA in disparate ways, obscuring a clear pattern of findings. This systematic review synthesizes the rapidly developing literature and clarifies the role of RSA in romantic relationships. We evaluate support for three conceptual hypotheses: (1) resting baseline RSA is associated with better quality relationships; (2) phasic RSA is reflective of changes in threat and connection during couple interactions; and (3) physiological linkage in RSA between romantic partners relates to positive or negative relationship functioning depending on the nature of the linkage (e.g., in-phase vs. antiphase). We identified 26 empirical studies that tested associations between RSA and an index of romantic relationships (i.e., relationship satisfaction). Our findings show that higher RSA is not uniformly \"good\" for relationships. Higher resting baseline RSA was contemporaneously associated with better quality relationships, yet higher baseline RSA was also unexpectedly associated with relationship violence. Short-term decreases in RSA were found during relationship conflict, though the opposite-phasic increases in RSA during positive romantic partner interactions-was not found due to mixed empirical support. As expected, evidence for RSA linkage was found, though the connection between linkage and relationship functioning depends on the context in which it was measured. We discuss methodological limitations and directions for future research.
La arritmia sinusal respiratoria (ASR), un índice del sistema nervioso parasimpático, ha sido objeto de atención recientemente como componente fisiológico de los procesos reguladores, la conexión social y la salud. Dentro del contexto de las relaciones amorosas, los estudios han operacionalizado y conceptualizado la ASR de diversas maneras, ocultando un patrón claro de signos. Este análisis sistemático sintetiza la bibliografía que se está desarrollando rápidamente y aclara el papel que desempeña la ASR en las relaciones amorosas. Evaluamos el respaldo de tres hipótesis conceptuales: (1) una ASR de reposo en el momento basal está asociada con relaciones de mejor calidad; (2) la ASR refleja cambios en la amenaza y la conexión durante las interacciones de la pareja; y (3) la asociación fisiológica en la ASR entre los integrantes de la pareja se relaciona con el funcionamiento positivo o negativo de la relación según la índole de la asociación (p. ej.: en fase frente a contrafase). Identificamos 26 estudios empíricos que evaluaron las asociaciones entre la ASR y un índice de las relaciones amorosas (p. ej.: la satisfacción con la relación). Nuestros resultados indican que una ASR más alta no es uniformemente “buena” para las relaciones. Una ASR de reposo más alta en el momento basal estuvo asociada contemporáneamente con relaciones de mejor calidad, sin embargo, una ASR más alta en el momento basal también estuvo asociada inesperadamente con la violencia de pareja. Se encontraron disminuciones de la ASR a corto plazo durante el conflicto en las relaciones, aunque no se encontró lo opuesto -aumentos fásicos en la ASR durante las interacciones positivas de los integrantes de la pareja- debido a un respaldo empírico ambivalente. Como se esperaba, se encontraron indicios de una asociación de la ASR, aunque la conexión entre la asociación y el funcionamiento de la relación depende del contexto en el cual se midió. Comentamos las limitaciones metodológicas y damos indicaciones para investigaciones futuras.
呼吸窦性心律失常(RSA)是副交感神经系统的一个指标，近期的研究中作为调节过程、社会联系和健康的一个生理组成部分受到关注。针对恋爱关系情境中进行的研究，对RSA的操作和概念化的研究方式有所差别，它们无法提供清晰的研究结果的模式。本文综合了快速增加的文献作了系统性的综述，明晰了RSA在爱情关系中的作用。我们评估了对三个概念性假设的支持。(1)静止时基线RSA与更好的关系质量相关；(2)阶段性RSA反映了伴侣互动过程中不良的兆头和伴侣连接关系方面的变化；(3)恋爱伴侣之间RSA的生理联动与积极或消极的关系功能有关，这取决于联动的性质(例如，同相联动与反相联动)。我们找出26项实证研究，这些研究测试了RSA与恋爱关系指数（即关系满意度）之间的关联。我们的研究结果表明，更高的RSA并不都是“好的”关系。较高的静止时基线RSA与较好的关系质量同时相关，然而较高的基线RSA也出乎意料地与关系暴力相关。在关系冲突期间，研究虽发现了短期的RSA下降，但在良好的恋爱伴侣互动中，出现反相联动的RSA增加的现象却尚未发现，这是由于有多种实证的支持。正如预期的那样，发现了RSA联动的证据，尽管这种生理联动和恋爱关系功能之间的联系取决于测量它的具体场景。本文也讨论了研究方法方面的局限性和未来的研究方向。.

Animal and human research suggests that the development of the autonomic nervous system (ANS) is particularly sensitive to early parenting experiences. The Still-Face Paradigm (SFP), one of the most widely used measures to assess infant reactivity and emotional competence, evokes infant self-regulatory responses to parental interaction and disengagement. This systematic review of 33 peer-reviewed studies identifies patterns of parasympathetic (PNS) and sympathetic (SNS) nervous system activity demonstrated by infants under one year of age during the SFP and describes findings within the context of sample demographic characteristics, study methodologies, and analyses conducted. A meta-analysis of a subset of 14 studies with sufficient available respiratory sinus arrhythmia (RSA) data examined whether the SFP reliably elicited PNS withdrawal (RSA decrease) during parental disengagement or PNS recovery (RSA increase) during reunion, and whether results differed by socioeconomic status (SES). Across SES, the meta-analysis confirmed that RSA decreased during the still-face episode and increased during reunion. When studies were stratified by SES, low-SES or high-risk groups also showed RSA decreases during the still face episode but failed to show an increase in RSA during reunion. Few studies have examined SNS activity during the SFP to date, preventing conclusions in that domain. The review also identified multiple qualifications to patterns of SFP ANS findings, including those that differed by ethnicity, infant sex, parental sensitivity, and genetics. Strengths and weaknesses in the extant research that may explain some of the variation in findings across the literature are also discussed, and suggestions for strengthening future research are provided.

This article is aimed at showing the current level of evidence for the usage of biofeedback and neurofeedback to treat depression along with a detailed review of the studies in the field and a discussion of rationale for utilizing each protocol. La Vaque et al. criteria endorsed by the Association for Applied Psychophysiology and Biofeedback and International Society for Neuroregulation & Research were accepted as a means of study evaluation. Heart rate variability (HRV) biofeedback was found to be moderately supportable as a treatment of MDD while outcome measure was a subjective questionnaire like Beck Depression Inventory (level 3/5, \"probably efficacious\"). Electroencephalographic (EEG) neurofeedback protocols, namely, alpha-theta, alpha, and sensorimotor rhythm upregulation, all qualify for level 2/5, \"possibly efficacious.\" Frontal alpha asymmetry protocol also received limited evidence of effect in depression (level 2/5, \"possibly efficacious\"). Finally, the two most influential real-time functional magnetic resonance imaging (rt-fMRI) neurofeedback protocols targeting the amygdala and the frontal cortices both demonstrate some effectiveness, though lack replications (level 2/5, \"possibly efficacious\"). Thus, neurofeedback specifically targeting depression is moderately supported by existing studies (all fit level 2/5, \"possibly efficacious\"). The greatest complication preventing certain protocols from reaching higher evidence levels is a relatively high number of uncontrolled studies and an absence of accurate replications arising from the heterogeneity in protocol details, course lengths, measures of improvement, control conditions, and sample characteristics.

Emotion regulation, the ability to regulate emotional responses to environmental stimuli, develops in the first years of life and plays an important role in the development of personality, social competence, and behavior. Substantial literature suggests a relationship between emotion regulation and cardiac physiology; specifically, heart rate changes in response to positive or negative emotion-eliciting stimuli.
This systematic review and meta-analysis provide an in-depth examination of research that has measured physiological responding during emotional-evoking tasks in children from birth to 4 years of age.
The review had three main findings. First, meta-regressions resulted in an age-related decrease in baseline and task-related heart rate (HR) and increases in baseline and task-related respiratory sinus arrhythmia (RSA). Second, meta-analyses suggest task-related increases in HR and decreases in RSA and heart rate variability (HRV), regardless of emotional valence of the task. Third, associations between physiological responding and observed behavioral regulation are not consistently present in children aged 4 and younger. The review also provides a summary of the various methodology used to measure physiological reactions to emotional-evoking tasks, including number of sensors used and placement, various baseline and emotional-evoking tasks used, methods for extracting RSA, as well as percentage of loss and reasons for loss for each study.
Characterizing the physiological reactivity of typically developing children is important to understanding the role emotional regulation plays in typical and atypical development.

The neurovisceral integration model posits that cognitive-behavioral inflexibility arises from biological inflexibility of feedback loops within the central autonomic network. The parasympathetic nervous system (PNS) is integral in this network. Activity of the PNS, which is normally tonically inhibited, can be indexed through respiratory sinus arrhythmia (RSA). When the PNS becomes disinhibited, indicating decreased flexibility within the network, RSA is reduced and cognitive-behavioral flexibility is impaired. Using this theoretical framework, cognitive-behavioral inflexibility is discussed from the Research Domain Criteria (RDoC) perspective. Restricted repetitive behaviors in autism spectrum disorder (ASD) are proposed as exemplars of cognitive-behavioral inflexibility, and behavioral and RSA literature in ASD are reviewed. RSA differences and their relation to inflexibility in ASD are discussed to support the model and to propose RSA as a biomarker for cognitive-behavioral inflexibility. Considerations for future research are discussed, in addition to implications the model might have on assessment and transdiagnostic treatment practices.