Oral Health-Related Quality of Life and Self-Reported Oral Health Status Are Associated with Change in Self-Reported Depression Status: A Cohort Study

<b>Background/Objectives</b>: Oral health-related quality of life (OHRQoL) may influence mental health outcomes, yet longitudinal evidence on its association with depression remains limited. This study aimed to examine whether oral health status and OHRQoL are associated with a change in self-reported depression status among adults in Japan. <b>Methods</b>: We analyzed data from the Japan COVID-19 and Society Internet Survey (JACSIS), conducted in 2022 and 2023. A total of 15,068 participants aged ≥20 years without depression at baseline were included. Depression status was identified by self-reported measures between the two survey waves. Logistic regression models estimated odds ratios (ORs) and 95% confidence intervals (CIs) for change in self-reported depression status in relation to OHRQoL and oral health status, adjusting for sociodemographic and behavioral factors. <b>Results</b>: During follow-up, 218 participants (1.45%) reported a change in self-reported depression status. Poorer OHRQoL was significantly associated with a change in self-reported depression status (OR: 1.018; 95% CI: 1.001-1.036; <i>p</i> = 0.039). Additional risk factors included younger age (OR: 0.974; 95% CI: 0.964-0.985), participation in hobbies and cultural activities (OR: 2.224; 95% CI: 1.498-3.302), habitual use of sleeping pills or anxiolytics (current use OR: 3.512; 95% CI: 2.267-5.442), increased loneliness (OR: 1.217; 95% CI: 1.140-1.299), lower life satisfaction (OR: 0.900; 95% CI: 0.836-0.969), and poor self-rated health (OR: 2.921; 95% CI: 1.810-4.715). <b>Conclusions</b>: Impaired OHRQoL was associated with a change in self-reported depression status, potentially through psychosocial mechanisms. These findings suggest that oral health and OHRQoL may be relevant factors to consider in integrated oral and mental health approaches in clinical practice.