Indirect Associations of Personality, Somatic Symptoms and Oral Behaviours in the Link Between Psychological Distress and TMD Symptom Severity

BACKGROUND: Temporomandibular disorders (TMDs) are multifactorial conditions affecting the masticatory system, with psychological distress increasingly recognized as a contributory factor. This study explored whether personality traits, somatization and oral behaviours are linked to the relationship between psychological distress and TMD symptom severity in young adults, by assessing their interrelationships and potential statistical pathways. METHODS: A cross-sectional study was conducted among 784 participants (mean age: 20.9 years; 66.1% female). Validated instruments included the Short-Form Fonseca Anamnestic Index, Patient Health Questionnaire (PHQ)-4, Big Five Inventory-10, PHQ-15 and Oral Behaviours Checklist. Statistical analyses comprised Mann-Whitney U, Chi-square, Spearman's correlation and Hayes' PROCESS macro (Models 1 and 4) to examine moderation and mediation in terms of indirect associations (α = 0.05). RESULTS: Symptoms consistent with TMDs were identified in 19.0% of participants. Moderate-to-severe psychological distress and somatization were significantly associated with greater TMD symptom severity, higher oral behaviour frequency and specific personality traits. Moderate correlations were observed among psychological distress, somatization, oral behaviours and TMD symptom severity (rs = 0.40-0.53). No significant moderation pathways were detected. Partial mediation pathways indicated indirect associations for psychological distress via agreeableness (β = 0.05), somatization (β = 0.46) and oral behaviours (β = 0.63), and for somatization via psychological distress (β = 0.12) and oral behaviours (β = 0.42). CONCLUSION: Psychological distress and TMD symptom severity showed indirect associations involving personality, somatization and oral behaviours. These findings highlight the value of biopsychosocial screening and culturally sensitive approaches for TMDs in young adults.