Extreme heat and mental health: systematic review and qualitative investigation of risk and protective factors

Clinical Snapshot

Key Findings

• P Value: Not reported

• Effect Size: Not reported; no quantitative pooling or meta-analytic effect sizes provided. Narrative synthesis identifies age, sex, pre-existing mental illness, ethnicity, and socioeconomic status as risk factors; good physical health, social support, and green space access as protective factors

• Primary Outcome: Identification of risk and protective factors for heat-related mental health impacts across 47 included studies, supplemented by qualitative themes from six focus groups

• Nnt Or Sensitivity: Not applicable; no NNT, sensitivity, specificity, or hazard ratio reported. The HEAT-MH screening tool (15 items) has not been validated; no diagnostic accuracy metrics are available

• Confidence Interval: Not reported

Clinical Application

The HEAT-MH tool is a 15-item questionnaire covering heat experience, general health, and lifestyle — administratively simple and low-cost if validated. However, clinical implementation is premature without psychometric validation, sensitivity/specificity data, and evidence of impact on clinical outcomes. Integration into routine mental health assessments during heatwaves is conceptually feasible but not yet evidence-based. Australia faces some of the world's most severe and frequent extreme heat events, making this research highly contextually relevant. The RACGP has highlighted climate change as a health priority, and heat-health action plans exist at state and territory levels. However, the UK-derived qualitative data and predominantly Northern Hemisphere study populations in the systematic review limit direct applicability. Australian-specific considerations include: the disproportionate heat burden on Aboriginal and Torres Strait Islander communities; the role of the PBS in funding psychotropic medications that may impair thermoregulation (e.g., antipsychotics, lithium, anticholinergics); TGA-approved medications with heat-related adverse effect profiles; and the need for RACGP-aligned heat-health guidance for GPs managing patients with serious mental illness. Australian validation of HEAT-MH would be required before any PBS or clinical guideline integration. Adults with pre-existing mental illness, older adults, people of lower socioeconomic status, and those with limited social support who are exposed to extreme heat events. Clinicians in psychiatry, general practice, and public health may find the risk factor framework useful for clinical reasoning, pending tool validation.

Abstract

BACKGROUND: Extreme hot weather poses increasing risks to mental health. Yet, factors affecting vulnerability are under-researched. This mixed-method study integrates a systematic review and qualitative investigation to identify risk and protective factors for heat-related mental health issues, leading to the co-development of a screening tool. This could inform future research and, pending validation in clinical settings, support mental health professionals in assessing vulnerability among service users. METHODS: We searched PubMed and Web of Science for publications on extreme heat, mental health, and risk/protective factors. In addition, we conducted six focus groups with 21 people with lived experience of heat and/or mental illness and 12 healthcare professionals. Transcripts were analyzed using thematic content analysis and informed the co-development of the screening tool. RESULTS: Out of 764 articles identified by the systematic review, 47 were included. Evidence emerged for age, sex, existing mental illness, ethnicity, and socioeconomic status as risk factors. However, findings were inconsistent between studies, likely due to differences in study population and methodology. Protective effects included good physical health, social support, and exposure to green spaces. Our qualitative investigation identified additional risk and protective factors related to: (1) behavioral adaptability, (2) personal heat sensitivity, and (3) disparities in heat exposure. The resulting screening tool, HEAT-MH (Heat Exposure Assessment Tool for Mental Health), contains 15 questions on previous experiences of heat, general health, and lifestyle. CONCLUSIONS: The mental health impacts of extreme heat depend on a range of risk and protective factors, including demographic, socioeconomic, health, and lifestyle characteristics.

References

1. 1.Baecker, L., Khan, M., Iyengar, U., Tadayon, A., & Mechelli, A. (2026). Extreme heat and mental health: systematic review and qualitative investigation of risk and protective factors. Psychological Medicine. https://doi.org/10.1017/S0033291726105169