Masseter ultrasonographic characteristics across clinically defined groups of antidepressant users and non-user controls: a cross-sectional study

Abstract Background Masseter ultrasonographic characteristics remain incompletely described in antidepressant users with differing clinical bruxism classifications. This study compared three predefined clinical groups. Methods This single-center cross-sectional study used prospectively acquired clinical and imaging data from 123 adults: antidepressant users with clinically defined probable bruxism and a self-reported temporal association (G1, n = 42), antidepressant users without probable bruxism (G2, n = 31), and non-antidepressant controls without probable bruxism (G3, n = 50). For G1, recalled onset or worsening of bruxism-related complaints after treatment initiation was recorded during anamnesis; this chronology was entirely retrospective. Bilateral thickness, estimated volume, and a reciprocal strain-elastography metric were measured at rest and during voluntary clenching; fractal dimension was calculated from resting images. Nonparametric comparisons, adjusted regression models, and secondary inter-parameter correlations were performed. Results G1 had higher resting and clenching thickness, estimated volume, reciprocal strain-elastography values, and resting fractal dimension than G2 and G3. Thickness, estimated volume, and the reciprocal strain-elastography metric increased from rest to clench in all groups. Between-group differences remained statistically evident in models adjusted for the measured covariates. Conclusions Masseter ultrasound-derived measurements differed among the predefined clinical groups. These findings do not establish the onset or progression of bruxism, a causal effect of antidepressant use, or a medication-specific muscle phenotype.