Association Between Psychological Factors and Masticatory Muscle Thickness Assessed by Ultrasonography in Female Dental Students with TMD-Related Myalgia: A Cross-Sectional Study

Objectives: The aim of this study was to compare the relationship between psychological factors and the thickness of masticatory muscles in patients with temporomandibular disorders (TMD) and healthy controls. Methods: This cross-sectional study included 106 female participants aged 18–35 years, recruited from students of the Medical University of Lublin. The study group consisted of individuals diagnosed with myalgia based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), while the control group included participants without TMD. Psychological factors were assessed using the PHQ-9, GAD-7, and PHQ-15 questionnaires. The thickness of the temporalis and masseter muscles was measured using an M-Turbo (Sonosite) ultrasound device under relaxed and contracted conditions. Results: Participants with TMD-related myalgia scored significantly higher on the PHQ-9 (mean ± SD: 8.82 ± 5.02 vs. 5.00 ± 3.41; p < 0.001), GAD-7 (8.53 ± 4.48 vs. 4.65 ± 3.58; p < 0.001), and PHQ-15 (9.47 ± 4.07 vs. 6.02 ± 3.89; p < 0.001) compared to controls. No statistically significant differences were observed in temporalis or masseter muscle thickness at rest or during contraction between groups (p > 0.05). Significant differences in correlations were found between depression scores and temporalis muscle thickness in the study group compared to the control group (r = 0.32 vs. −0.13, p = 0.011) as well as between anxiety scores and temporalis muscle thickness (r = 0.25 vs. −0.30, p = 0.002) No significant associations were found for the masseter muscle. Conclusions: Individuals with myalgia did not show increased muscle thickness compared to healthy individuals. Psychological distress, particularly depression and anxiety, was differentially related to temporalis muscle morphology in individuals with myalgia compared to healthy controls.