CMD as an Indicator of Altered Physiological Stress Reactivity: A Highly Standardized Experimental Protocol

Background: Craniomandibular dysfunction (CMD) is a multifactorial disorder frequently associated with psychological stress. Its prevalence is particularly high in populations exposed to significant stress, such as students during exam periods. While subjective assessments have linked CMD to psychological stress, physiological evidence remains limited. Heart rate variability (HRV) is an established biomarker for autonomic regulation and stress reactivity, making it a valuable tool for assessing stress responses in CMD. Objective: This study examines stress reactivity in students with and without CMD symptoms using HRV as a physiological marker and a standardized stress protocol. Methods: A total of 138 healthy students (aged 23–36 years) were recruited. CMD symptoms were assessed using a standardized protocol based on the bruxism guideline , focusing on palpation-induced pain and range of motion limitations. Psychological stress was measured using the Perceived Stress Scale (PSS) and Beck Depression Inventory-II (BDI-II). Acute stress was induced using the Trier Social Stress Test (TSST), and HRV was recorded at baseline (pre-stress) and during stress exposure. RR intervals were analyzed using KUBIOS software, with root mean square of successive differences (RMSSD) as a key parameter. Statistical analyses employed linear mixed models, adjusting for confounders such as age, sex, and baseline stress levels. Results: CMD symptoms, especially pain caused by palpation, correlated significantly (p < 0.0048) with psychological stress markers. These students also had higher levels of depression (p < 0.0015). Due to participant dropout, the statistical significance of the analysis of heart rate variability was limited. The effect differences indicated a trend towards prolonged autonomic dysregulation in students with CMD pain. Conclusion: The findings provide physiological evidence linking CMD to stress, and show altered autonomic responses in students with CMD symptoms. Early symptom recognition, stress management programs and strategies should be integrated into CMD treatment. Future research should include cortisol as an additional biomarker and employ larger, longitudinal studies to improve clinical applicability.