Oral Health-Related Quality of Life and Oral Health Status Are Associated with the Development of Depression: A Longitudinal Study

Background/Objectives 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 the development of depression among adults in Japan. Methods 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 onset was identified by self-reported measures between the two survey waves. Logistic regression models estimated odds ratios (ORs) and 95% confidence intervals (CIs) for depression development in relation to OHRQoL and oral health status, adjusting for sociodemographic and behavioral factors. Results During follow-up, 218 participants (1.45%) developed depression. Poorer OHRQoL was significantly associated with development of depression (OR: 1.018; 95% CI: 1.001–1.036; p = 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). Conclusions Impaired OHRQoL was associated with depression development, potentially through psychosocial mechanisms. Maintaining good oral health and OHRQoL may help prevent depression, highlighting the need for integrated oral and mental health strategies in clinical practice.