Mental health is an important public health issue globally. A potential link between heat exposure and mental health outcomes has been recognised in the scientific literature; however, the associations between heat exposure (both high ambient temperatures and heatwaves) and mental health-related mortality and morbidity vary between studies and locations. To fill gaps in knowledge, this systematic review aims to summarize the epidemiological evidence and investigate the quantitative effects of high ambient temperatures and heatwaves on mental health-related mortality and morbidity outcomes, while exploring sources of heterogeneity. A systematic search of peer-reviewed epidemiological studies on heat exposure and mental health outcomes published between January 1990 and November 2020 was conducted using five databases (PubMed, Embase, Scopus, Web of Science and PsycINFO). We included studies that examined the association between high ambient temperatures and/or heatwaves and mental health-related mortality and morbidity (e.g. hospital admissions and emergency department visits) in the general population. A range of mental health conditions were defined using ICD-10 classifications. We performed random effects meta-analysis to summarize the relative risks (RRs) in mental health outcomes per 1 °C increase in temperature, and under different heatwaves definitions. We further evaluated whether variables such as age, sex, socioeconomic status, and climate zone may explain the observed heterogeneity. The keyword search yielded 4560 citations from which we identified 53 high temperatures/heatwaves studies that comprised over 1.7 million mental health-related mortality and 1.9 million morbidity cases in total. Our findings suggest associations between heat exposures and a range of mental health-related outcomes. Regarding high temperatures, our meta-analysis of study findings showed that for each 1 °C increase in temperature, the mental health-related mortality and morbidity increased with a RR of 1.022 (95%CI: 1.015-1.029) and 1.009 (95%CI: 1.007-1.015), respectively. The greatest mortality risk was attributed to substance-related mental disorders (RR, 1.046; 95%CI: 0.991-1.101), followed by organic mental disorders (RR, 1.033; 95%CI: 1.020-1.046). A 1 °C temperature rise was also associated with a significant increase in morbidity such as mood disorders, organic mental disorders, schizophrenia, neurotic and anxiety disorders. Findings suggest evidence of vulnerability for populations living in tropical and subtropical climate zones, and for people aged more than 65 years. There were significant moderate and high heterogeneities between effect estimates in overall mortality and morbidity categories, respectively. Lower heterogeneity was noted in some subgroups. The magnitude of the effect estimates for heatwaves varied depending on definitions used. The highest effect estimates for mental health-related morbidity was observed when heatwaves were defined as "mean temperature ≥90th percentile for ≥3 days" (RR, 1.753; 95%CI: 0.567-5.421), and a significant effect was also observed when the definition was "mean temperature ≥95th percentile for ≥3 days", with a RR of 1.064 (95%CI: 1.006-1.123). Our findings support the hypothesis of a positive association between elevated ambient temperatures and/or heatwaves and adverse mental health outcomes. This problem will likely increase with a warming climate, especially in the context of climate change. Further high-quality studies are needed to identify modifying factors of heat impacts.

One Health (OH) recognizes the interconnectedness of humans, animals, and their shared environment and mobilizes multiple sectors to achieve sustainable and optimal health outcomes. We synthesized current OH implementations at global, regional, national, and local community levels using the OH Joint Plan of Action (OH JPA) developed to enhance best practices in OH implementation. We applied the OH JPA Theory of Change, supported by three pathways mapped out across six action tracks to guide our review. Searches were conducted in PubMed, Embase and Scopus. Eligibility of studies was based on implementation of OH undertaken across two or more sectors within the human-animal-environment interface. Selection was guided by the PRISMA-ScR. Of the 54 studies, 77 unique programs reported OH implementations, and of these, 42 (54.5 %) involved human and animal sectors only. No studies involved the environment sector and its impact on human-environment or animal-environment. The majority (90.9 %) of programs incorporated at least one aspect of policy, legislation, advocacy and financing (Pathway 1). Capacity development, community engagement, multisectoral coordination, collaboration or communication was identified in 96.1 % of programs (Pathway 2). Data, evidence and knowledge featured in 60 % of OH initiatives (Pathway 3). Pathway 2 was the most engaged pathway building the foundation for OH implementation and action. There is opportunity for further growth concerning community engagement, monitoring and evaluation strategies with enhanced future investment for implementation of community-centric and risk-based solutions. Furthermore, it is important to foster better understanding of environmental issues and to build capacity for the environment sector to be better represented in the implementation of OH.

Background and Aims: Cardiovascular disease (CVD), the leading cause of death globally and in Australia, is sensitive to heat exposure. This study assesses the burden of CVD attributable to high temperatures across Australia and projects future burden in the context of climate change. Methods: Disability-adjusted life years for CVD, including years of life lost and years lived with disability, were sourced from the Australian Burden of Disease database. A meta-regression model was constructed using location-specific predictors and relative risks from prior literature to estimate relative risks of CVD mortality and morbidity due to high temperatures in the Australian context. The baseline CVD burden attributable to high temperatures in Australia for 2003–18 was calculated, and future burdens under two greenhouse gas emissions scenarios [Representative Concentration Pathways (RCP4.5 and RCP8.5)] for the 2030s and 2050s were projected, considering demographic changes and human adaptation. Results: During the baseline period, high temperatures accounted for 7.3% (95% confidence interval: 7.0%–7.6%) of the CVD burden in Australia, equivalent to 223.8 Disability-adjusted life years (95% confidence interval: 221.0–226.6) per 100 000 population. Future projections suggest a steady increase in the CVD burden across all scenarios examined. By the 2050s, under the RCP8.5 scenario that considers population growth and no adaptation, the total attributable burden of CVD is projected to more than double compared with the baseline, with the Northern Territory facing the most significant increase. These impacts could be mitigated with effective human adaptation to the warming climate. Conclusions: Higher temperatures are expected to exacerbate the burden of CVD. This study highlights the need for urgent adaptation and mitigation efforts to minimize the negative health impacts of a warming climate on CVD.