Interactions between COVID-19 lockdown and ambient carbon monoxide on child and adolescent psychiatric outpatient visits: A time-series study in Shenzhen, China

Background The COVID-19 pandemic has been reported changes in environmental composition and increased mental stress. However, the findings are inconsistent. We aimed to confirm the impact of the COVID-19 lockdown on the change of environment and the child and adolescent attending psychiatric clinics (CAPC) visits in China. And reveal the interact relationship between environmental factors and COVID-19 on CAPC visits. Methods A case-crossover study utilizing time-series data was conducted. Least absolute shrinkage and selection operator (LASSO) regression was employed to address multicollinearity among covariates and select variables. A distributed lag non-linear model (DLNM) was utilized to examine the non-linear and delayed effects of the two major environmental factors on CAPC visits. The interaction analysis was conducted based on the results of DLMN. Result We finally collected 439313 CAPC outpatients who were aged at 3–18 from 2016 to 2022 in Shenzhen, China. We found that the COVID-19 lockdown may alter the levels of certain environmental factors. Additionally, we observed a significant increase in CAPC visits during the COVID-19 visits (p < 0.05). We also found that The CO may interact with the lockdown and affect CAPC visits. Conclusion Our findings suggest that there may be an interaction between the environment and COVID-19, that the lockdown could further affect the children and adolescents’ mental health by interact with CO. These findings highlight the transactional nature between environmental change and psychological response among children and adolescents during the lockdown period, offering new insights from an environmental psychology perspective.