Synergistic effects of short-term co-exposure to temperature and air pollution on acute mental and behavioural disorders.

<ns3:p> Background Exposure to extreme temperatures and air pollution have been linked to an increasing number of morbidity outcomes, including mental and behavioural conditions. Studies assessing impacts of such short-term exposures have typically focused on individual environmental risk; however, there is emerging evidence that extreme temperatures and air pollution co-exposures may act synergistically to influence human health, including mental and behavioural disorders. Therefore, a comprehensive critical synthesis which considers the interactive effects of short-term changes in temperature and air pollution on acute mental and behavioural outcomes is required to inform climate adaptation and mitigation strategies. Methods and analysis This systematic review protocol follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guidelines. A systematic search was conducted across (MEDLINE, Ovid, Scopus, PsycINFO, Web of Science, and GreenFILE (30 <ns3:sup>th</ns3:sup> of November 2024) to identify relevant articles published between January 2000 and October 2024. We will include all relevant quantitative observational study designs including cohort, cross-sectional, ecological studies, and time-series analyses. Both title and abstract and full text screening will be performed by two independent reviewers. The quality assessment will be done using a modified Risk of Bias Assessment Instrument for Systematic Reviews Informing WHO Global Air Quality Guidelines. We will undertake narrative synthesis identifying key themes such as the combination of meteorological and air pollutant exposures and mental health or behavioural disorder outcomes. We have prespecified subgroup analyses based upon exposure, outcome and study context classification. Where appropriate, if sufficient comparable studies are identified, a meta-analysis will be conducted. Heterogeneity will be investigated using a combination of the I <ns3:sup>2</ns3:sup> statistic results to explore performing a meta-analysis. Authorship Abeer Albdour, Chee Yap Chung, Zongbo Shi, Ajit Singh, James Hall, Suzanne Bartington. On behalf of the WM Net Zero study team. Ethics and dissemination No original data will be collected for this review. Findings will be disseminated through peer-reviewed publications and conference presentations. Ethical Approval: ERN_1825-Dec2023 Public and Patient Involvement Members of the WM Net Zero Public Involvement in Research Group (PIRG) will provide input to the conduct, reporting, interpretation and dissemination of the review. PROSPERO registration number CRD42024555900 </ns3:p>