Abstract
Mental and behavioral disorders (MBDs) represent a significant global health challenge. Nitrogen dioxide (NO2), a prevalent urban air pollutant with potential neurotoxicity, has been studied for its acute effects on MBDs. However, existing evidence remains limited and inconsistent. A time-series study of over 10 years was conducted in Xinxiang, China, to investigate the acute effects of NO2 on outpatient visits for MBDs from 1 January 2015 to 30 June 2025. The analysis comprised 2,409,583 valid records. A generalized additive model (GAM) with a quasi-Poisson distribution was utilized, with adjustments for long-term temporal trends, meteorological variables, weekday effects, and public holidays. For every 10 µg/m³ increase in NO2 concentrations at lag0, outpatient visits for MBDs increased by 2.54% (95% CI: 2.04%, 3.04%). This effect was stronger during the cool season. The exposure-response (E-R) curve indicated a potential non-linear relationship, but the estimates at high concentrations are uncertain. Results from sensitivity analyses indicated no substantial changes in effect estimates. Our findings demonstrate that short-term NO2 exposure was linked to elevated outpatient visits for MBDs, particularly in the cool season, thereby supporting the need for air pollution control and mental health protection.