Background Although psychological factors have been implicated in patients with functional dysphonia (FD), conventional voice therapy (CVT) typically targets the aberrant voice symptoms exclusively. Yet, CVT is not always successful, and in view of the significant adverse quality of life impact combined with the financial burden on the healthcare system and society, research is needed to elucidate the underlying psychophysiology of FD and improve treatment outcomes. Objectives The first objective of this research project is to compare the occurrence and frequency of symptoms and/or disorders related to autonomic nervous system (ANS) dysfunction in patients with FD with gender- and age-matched vocally healthy controls, using a case-control study. The second objective is to compare the effects of a novel therapy for FD based on ANS regulation (i.e., ANS therapy: heart rate variability (HRV) biofeedback) on both autonomic function and voice function versus CVT alone or in combination with ANS therapy (i.e., ANS therapy + CVT), using a randomized controlled trial (RCT). Methods Case-control study: Autonomic (dys)function of patients with FD will be compared with gender- and age-matched vocally healthy controls, using both physiological measures (e.g., HRV, skin conductance level) and psychological patient-reported outcome measures (PROMs, e.g., Neuroception of Psychological Safety Scale, Depression Anxiety and Stress Scale). RCT: The FD group will be randomly assigned to the innovative ANS therapy group, the CVT group or the ANS therapy + CVT group. All patients received 1 month of treatment with 20 min of daily practice. Both the autonomic assessment and the voice assessment will be performed pretherapy and immediately after therapy by assessors blinded to group allocation and study phase. Expected results Higher occurrences of symptoms and/or disorders related to autonomic dysfunction are expected in patients with FD compared with vocally healthy controls. Physiological outcomes: lower HRV, lower cardiac pre-ejection period, higher respiration rate and higher skin conductance level are hypothesized in patients with FD compared with vocally healthy controls. Psychological PROMs: higher self-report of feelings/symptoms related to autonomic dysfunction (e.g., perceived stress, anxiety) is expected in patients with FD compared with vocally healthy controls. The autonomic function is hypothesized to improve more after the ANS therapy and the ANS therapy + CVT compared with the CVT only. Voice function is expected to improve more after the ANS therapy + CVT compared with the ANS therapy and the CVT alone. WHAT THIS PAPER ADDS What is already known on the subject Autonomic dysfunction is well recognized in the field of psychology but remains understudied in the area of voice. Given that the vagus nerve, innervating the larynx, also helps to regulate the ANS, and psychological symptoms commonly observed in patients with FD may reflect ANS dysregulation, research in this area is needed. There is some preliminary evidence that autonomic dysfunction might indeed be associated with FD. However, physiological ANS measures are needed, as well as validated psychological PROMs. What this paper adds to the existing knowledge The first objective of this study is to investigate the occurrence and frequency of symptoms and/or disorders related to autonomic dysfunction in patients with FD as compared with a gender- and age-matched vocally healthy control group. Autonomic (dys)function will be determined by employing both physiological measures (e.g., HRV, skin conductance level) and psychological PROMs (e.g., Neuroception of Psychological Safety Scale, Depression Anxiety and Stress Scale). The second objective is to compare the effects of a novel therapy for FD based on ANS regulation (HRV biofeedback) versus CVT alone or in combination with ANS therapy. What are the potential or actual clinical implications of this work? Success rates of symptomatic CVT for FD are highly variable. This study is expected to lead to innovative results related to the pathogenesis and psychophysiology of FD, a prevalent voice disorder associated with a significant adverse quality of life impact and a substantial financial burden on the healthcare system and society. The results of this study will lead to crucial new insights into both the diagnosis and treatment of FD, contributing to evidence-based practice in the field of voice.

Objective: 
This single-blind randomized controlled laboratory experiment investigated the impact of resonant breathing on adolescents’ autonomic nervous system (ANS) and affective responses to a standardized acute stressor.
Methods: 
Adolescents (n=150, 12-13y, 40% boys) were randomized into two conditions: resonant breathing (RB condition) or spontaneous breathing (active control condition), both with visual guidance. In this registered report (https://osf.io/8swdp), mixed-effects models compared conditions on cardiac ANS (heart rate variability RMSSD, pre-ejection period PEP) and affective responses (positive and negative affect) to the Trier Social Stress Test, across reactivity and recovery phases. Additionally, conditions were compared on rumination and reappraisal use.
Results: 
The determined resonant rate showed a narrow interquartile range (6.2-6.7 breaths/min) and proved difficult to sustain during the 10-minute exercise. The RB intervention significantly reduced breathing rate (Cohen’s d=−4.69) and increased RMSSD during the breathing phase (d=1.68). Compared to the control condition, PEP reactivity to the stressor was attenuated in the RB condition (d=0.32), supporting a protective effect. Unexpectedly, RMSSD stress reactivity was more pronounced in the RB condition (d=−1.37), though this effect diminished in sensitivity analyses, suggesting regression to the mean. Exploratory analyses indicated that among adolescents with lower trait stress-related symptoms, RB reduced RMSSD stress reactivity relative to baseline (d=0.75). No differences between conditions were found in affective responses, emotion regulation, or stress recovery.
Conclusions: 
The findings only partially support the hypothesis that RB buffers physiological stress reactivity, with no observed effects on affect or recovery. Repeated training may be essential for achieving the resonant rate and potentially enhancing stress-buffering capacity.