Ozone Exposure (Outdoor–Indoor–Personal) and Mental Health in Young Adults

Mental disorders pose a growing threat to young adults globally. While ozone exposure has been linked to anxiety and depression, reliance on ambient measurements may misrepresent personal exposure. This study examined associations between ozone exposure at ambient, indoor, and personal levels and anxiety symptoms, depressive symptoms, and sleep disturbance among young adults, and assessed sleep quality as a potential mediator. A nationwide cross-sectional survey (2023-2024) was conducted across 261 Chinese municipalities. Annual maximum 8-h ozone concentrations over the preceding year were estimated at outdoor, indoor, and personal exposure levels. Validated scales were used to assess anxiety symptoms (GAD-7), depressive symptoms (PHQ-9), and sleep quality (PSQI). Multivariable logistic regression and mediation analysis within a logistic framework were applied, adjusting for sociodemographic, behavioral, and health condition covariates. Among 13,028 participants, the prevalence of anxiety symptoms, depressive symptoms, and sleep disturbance was 14%, 19%, and 39%, respectively. Associations with anxiety and depressive symptoms varied modestly across outdoor, indoor, and personal ozone exposure. Per interquartile range increase in outdoor, indoor, and personal ozone concentrations, odds ratios for anxiety were 1.17, 1.19, and 1.14; corresponding estimates for depression were 1.14, 1.13, and 1.10. Sleep quality mediated 10-30% and 16-49% of the ozone-anxiety and ozone-depression associations, respectively. These findings suggest that incorporating indoor and personal exposure metrics may provide additional insight into ozone-related mental health risks, with sleep quality serving as a mediator.