Salivary Cortisol Levels and Temporomandibular Disorders – A Systematic Review and Meta-Analysis of 13 Case-Control Studies

Purpose: To compare salivary cortisol levels between patients with temporomandibular disorders (TMD) and healthy controls.Methods: Pubmed, EMBASE, Web of Science and PsycINFO databases were employed to screen for the included studies. RevMan 5.3 software and RStudio software were used for meta-analysis, while a random-effect model was selected to synthesize the effect with the mean difference (MD).Results: Thirteen studies were eligible and a total of 504 TMD patients and 410 controls were included. The pooled MD of salivary cortisol levels in TMD patients compared to controls was 0.05 (95 %CI = 0.01 - 0.09, p = 0.02), indicating a significantly higher level of salivary cortisol in TMD patients than in the controls. Subgroup analysis suggested studies published later than 2014 showed significant increase of salivary cortisol level in TMD patients when compared to controls (MD = 0.07, 95 % CI = 0.01-0.13, p = 0.03). Besides, high-quality studies presented significant differences with regard to the cortisol level in saliva among individuals with or without TMD (MD = 0.04, 95 %CI = 0.03-0.05, p < 0.01). However, the instability of the results showed by the sensitivity analysis was a hindrance to reaching a definitive conclusion.Conclusion: The findings of this study indicate that salivary cortisol level in TMD patients is significantly higher than in controls. Consequently, supportive psychological treatment is recommended to prevent TMD patients from mood disorders. More high-quality studies are, however, needed to confirm the relationship, considering the high degree of heterogeneity among the studies.