The systematic review and meta-analysis were conducted in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (34). Comprehensive literature searches were performed in PubMed, Web of Science, Cochrane Library, PsycINFO, Scopus, ProQuest, and Embase databases, covering publications up to April 16, 2024, without restrictions on publication date. The search strategy utilized both controlled vocabulary and free-text terms related to climate change (e.g., “climate change,” “global warming,” “heat stress”), suicide and self-harm (e.g., “suicide,” “suicidal ideation,” “self-injury”), and gender variations (e.g., “sex characteristics,” “gender differences,” “sexual dimorphism”). Boolean operators were applied to structure the search and improve specificity. Each identified study was screened for relevance, with eligibility independently assessed by two reviewers. An overview of the full search strategy and terms used is provided in Supplementary Table 1.

For inclusion in the systematic review and meta-analysis, studies had to meet the following criteria: (1) The research must have investigated the impact of climate change on suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety. Anxiety was included as it has a well-documented link with climate change-related stressors and plays a potential role in exacerbating suicidality (35). Although depression and substance use disorder are also important considerations, anxiety was prioritized in this review due to its frequent occurrence in climate-related mental health studies and its relevance to the gender-specific analysis of mental health vulnerabilities. (2) The studies were required to provide gender-specific data on these outcomes or allow for such data to be derived from secondary sources. (3) Both observational and experimental study designs were considered eligible.

The exclusion criteria were as follows: (1) Studies with incomplete data were excluded. (2) Studies published in languages other than English were not considered. (3) Studies were excluded if the full text was not accessible. (4) Research that combined multiple outcome measures without enabling separate analysis was excluded. (5) In cases of participant overlap across studies, the earliest published study was excluded to prevent data duplication.

To ensure data integrity, two researchers independently extracted the data. Any discrepancies were resolved through consultation with a third reviewer who has expertise in the relevant field. The data extracted from each study included: author name, publication year, study location, recruitment period, and participant characteristics such as age and gender. Outcome measures focused on the prevalence of suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety, disaggregated by gender, as well as climate variables such as temperature, atmospheric pollution levels, and desertification indicators, recorded with standardized measurement techniques where applicable. In cases where data were not directly available, we calculated estimates based on secondary sources or inferred values from reported rates to ensure accuracy and consistency. Additionally, we categorized climate variables to facilitate subgroup and sensitivity analyses later in the study. A protocol-guided approach ensured that each stage of data extraction followed a consistent methodology, and our extraction records were carefully documented to enable reproducibility of the findings and enhance transparency in the meta-analytic process.

Statistical analyses were performed using Stata (version 11.0 for Windows) to assess the relationship between climate change and mental health outcomes, including suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety, by gender. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for each outcome. Meta-regression was conducted for suicide deaths and anxiety to examine the influence of key covariates, including weather conditions, study design, gender ratio, country classification, and total sample size. These outcomes were selected for meta-regression based on their homogeneity and the availability of sufficient data. For weather conditions, regions with an average annual temperature above 30°C were categorized as “high temperature” (value = 1), while all other regions were classified as “other” (value = 2). Although specific environmental phenomena such as cold weather, thunderstorms, and rainstorms were evaluated for their impact on mental health outcomes, these were treated separately from the weather category in the meta-regression model.

Due to substantial heterogeneity in measurement methods, sample sizes, and reporting across studies, meta-regression was not performed for other outcomes, such as suicidal ideation, suicide attempts, and self-harm. Subgroup analyses were conducted to explore sources of heterogeneity, categorized by continent, study design, weather exposure type, and gender. Gender-specific subgroup analysis was carried out by grouping studies into male (m1, m2) and female (f1, f2) categories, as shown in Supplementary Figures 1A–5A. Heterogeneity was assessed using the I² index and the Q-test, while publication bias was examined using funnel plots and Egger's test.

Each study's quality was evaluated using the Newcastle-Ottawa Scale (36). This scale assesses selection of study groups, comparability between groups, and outcome assessment for cohort studies or exposure for case-control studies. Studies were scored from 0 to 9, with higher scores indicating better quality. Two reviewers independently assessed each study and resolved any differences through discussion. Studies were classified into low, moderate, or high quality based on their scores. Detailed results and classifications are provided in Supplementary Table 2.

Suicide outcomes in this study were classified into four categories: suicidal ideation, suicide attempts, suicide deaths, and self-harm. Suicidal ideation refers to thoughts of self-harm or ending one's life without physical action, representing an early stage of suicide-related behavior and often indicating underlying psychological distress (37, 38). Suicide attempts, in contrast, involve intentional actions aimed at self-harm or death, marking an escalation of suicidal behavior driven by acute emotional pain and external stressors (39–41). Suicide deaths are the final and irreversible outcome of suicide-related behaviors, where the individual deliberately ends their life, typically following prolonged psychological distress or pre-existing mental health conditions (42–44). Self-harm, distinct from the other outcomes, involves deliberate, non-fatal injury to oneself as a maladaptive coping mechanism for emotional turmoil. While self-harm is not driven by a desire to die, it often serves as a temporary release from psychological pain and is frequently seen as a precursor to more severe suicide-related behaviors (45, 46). These definitions provide the basis for the classification and analysis of suicide-related outcomes in this study, ensuring consistency across the results.

A comprehensive search was conducted across seven databases—PubMed (38), Web of Science (433), Embase (28), Cochrane Library (7), PsycINFO (56), Scopus (311), and ProQuest (123)—yielding a total of 996 studies. After 318 duplicates were removed, 678 unique records remained for screening. Following the title and abstract screening, 409 records were excluded, and 269 articles were selected for full-text review. Further exclusions were made based on factors such as lack of gender-specific suicide data (172), case reports (10), and other irrelevant content, including meta-analyses or reviews (44). In the end, 36 studies met the eligibility criteria and were included in the meta-analysis. The detailed selection process is outlined in Figure 1.

A total of 36 studies were included in this analysis, conducted across various continents: America, Asia, Europe, Oceania, and Africa. Participants ranged in age, and the studies spanned multiple climate conditions such as high temperatures, atmospheric pollution, and desertification. The studies examined outcomes related to suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety. Detailed characteristics of each study, including author, year, study design, demographics, and climate variables, are summarized in Table 1.

This section critically examines the associations between climate variables—high temperature, atmospheric pollution, desertification, and other extreme weather phenomena—and mental health outcomes, including suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety. By disaggregating results by climate variable and considering geographic differences, this analysis highlights the distinct impacts of these environmental factors on suicide-related outcomes and anxiety. Supplementary Figures support the presentation of pooled estimates and subgroup analyses.

This section delves into the associations between distinct suicide-related outcomes—suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety—and climate change variables. By systematically analyzing results for each outcome and incorporating findings from sensitivity tests, subgroup analyses, and meta-regression, it seeks to unravel the unique pathways through which environmental factors shape these mental health outcomes. Supplementary Figures are provided to substantiate the robustness and reliability of the observed associations.

The impact of high temperature on mental health is dual-faceted, with both protective and harmful effects observed across different regions. In areas such as Kenya and India, where populations have adapted to prolonged heat exposure, high temperatures were inversely associated with suicidal ideation, likely due to enhanced social resilience and coping mechanisms. However, in regions like Oceania, recurrent heatwaves, combined with poor infrastructure and limited healthcare access, exacerbated mental health vulnerabilities, leading to an increased risk of suicide attempts and deaths. These findings emphasize the importance of context in shaping the relationship between temperature and mental health outcomes, suggesting that adaptive strategies can mitigate risks in certain regions, while other areas require targeted public health interventions to enhance resilience.

Atmospheric pollution, particularly in urban and industrialized regions, emerged as a significant environmental stressor with detrimental effects on mental health. Prolonged exposure to pollutants, such as PM2.5, was associated with an increased risk of suicide attempts and deaths, possibly through neuroinflammatory and oxidative stress mechanisms that exacerbate psychological vulnerability. While anxiety showed an inverse relationship with atmospheric pollution, this unexpected finding may reflect regional differences in healthcare access, reporting biases, or cultural norms influencing symptom recognition. These results underline the need for policies aimed at reducing air pollution and improving urban living conditions to mitigate the mental health impacts of poor air quality.

Desertification, although less impactful than other climate variables, demonstrated protective effects in regions prone to arid conditions, such as Kenya and India. In these areas, community-based coping mechanisms and enhanced social support networks appear to buffer against psychological distress, leading to a significant inverse association with suicidal ideation and anxiety. However, the mental health impact of desertification on more severe outcomes like suicide attempts and deaths remains poorly understood, with limited data available for robust analysis. Further research is needed to explore the long-term psychological consequences of desertification, particularly in underrepresented regions, to guide interventions that strengthen community resilience and mental health support.

Extreme weather events, including thunderstorms, hailstorms, and rainstorms, had more context-dependent impacts on mental health outcomes. While thunderstorms and hailstorms were linked to increased impulsivity and suicide attempts, the effects of rainstorms were more variable, likely due to regional differences in flood severity and disaster preparedness. Extreme weather events tend to disrupt both environmental and social systems, leading to acute psychological distress. These findings highlight the need for localized interventions to strengthen disaster response systems and mental health support in regions vulnerable to such events. Particularly in areas with inadequate disaster management or low socioeconomic resilience, extreme weather can exacerbate existing mental health conditions, underscoring the importance of context in determining the mental health impact of climate phenomena.

Our meta-analysis incorporated data from four studies, encompassing 2,767 male and 2,328 female participants, to assess the prevalence of suicidal ideation in the context of climate change. The results revealed a higher prevalence of suicidal ideation among females, 21.2% (95% CI: 19.59–22.90), compared to males, 15.3% (95% CI: 13.99–16.66). This suggests that females may be more susceptible to the psychological stressors associated with climate change. This gender disparity aligns with existing literature, which often attributes higher rates of mental health issues in females to factors such as increased caregiving responsibilities and greater economic vulnerabilities during extreme weather events (47). Moreover, the pooled odds ratio for suicidal ideation related to climate change was 0.73 (95% CI: 0.63–0.85), underscoring a significant inverse association with specific environmental factors such as desertification and atmospheric pollution. These findings suggest that long-term exposure to these stressors may foster certain protective mechanisms, such as enhanced psychological resilience or community-level adaptations, particularly in regions like India or urban centers in the USA and Kenya (48, 49).

The mechanisms underlying these associations remain complex and multifactorial. Gender-specific differences, including biological susceptibility to stress, sociocultural roles, and access to coping resources, may contribute to these disparities. Furthermore, unlike suicide attempts or deaths, suicidal ideation is less influenced by acute external stressors and may instead reflect cumulative psychological burdens exacerbated by prolonged exposure to climate stressors. These distinctions highlight the necessity of tailoring preventive strategies to address the unique pathways through which climate factors influence suicidal ideation, ensuring interventions are sensitive to both gender and regional vulnerabilities.

Our analysis, encompassing data from eight studies with 52,681 male and 40,732 female participants, revealed that suicide attempts were more prevalent among males, at 15.6% (95% CI: 15.28–15.91), compared to females, at 11.6% (95% CI: 11.26–11.88). This gender disparity highlights the distinct ways in which men and women respond to climate-related stress. Men, often subjected to societal pressures and cultural norms emphasizing stoicism and economic responsibility, may be less likely to express emotions or seek mental health support. Consequently, they are more prone to extreme responses, such as suicide attempts, under severe stress (50). This aligns with broader mental health research, which suggests that men's reluctance to seek help or share emotional burdens can lead to the accumulation of unaddressed psychological distress, culminating in drastic actions. Conversely, women are more likely to report mental health issues, such as anxiety and depression, but these may not translate into suicide attempts or deaths at the same rate. Women's coping mechanisms, which often involve seeking social support and engaging in emotional expression, may serve as protective factors against transitioning from ideation to attempts (51). This distinction underscores the need to address gender-specific pathways in understanding suicide attempts. Climate-induced stressors, such as economic instability, loss of livelihood, and displacement, may disproportionately impact men. The traditional expectation for men to be primary economic providers intensifies the psychological burden of these challenges, potentially exacerbating their vulnerability to suicide attempts. Meanwhile, women's higher rates of suicidal ideation may reflect chronic psychological distress, but their coping strategies and access to stronger social support networks may act as a buffer, preventing the progression to attempts (52, 53).

Data from 13 studies involving 51,260 male and 35,029 female participants revealed a higher prevalence of suicide deaths among males, at 14.2% (95% CI: 13.86–14.67), compared to females, at 9.3% (95% CI: 9.02–9.63). This gender disparity aligns with well-documented epidemiological trends, wherein men are more likely to complete suicide than women.

The heightened risk for males may be attributed to societal norms that emphasize economic provision and stoicism. During climate-induced crises, such as economic instability or resource scarcity, these expectations can intensify psychological stress, potentially leading to an increased likelihood of suicide deaths (54). Men may also experience barriers to seeking emotional or psychological support, contributing to the accumulation of unaddressed distress and a higher risk of fatal outcomes. Additionally, the physiological effects of extreme climate events, such as heatwaves, which exacerbate mental health conditions, may further amplify risks among vulnerable male populations.

In contrast, women, while facing significant psychological burdens due to climate change, often exhibit lower suicide death rates. This may be partly explained by their higher likelihood of seeking social and psychological support, as well as their reliance on established coping mechanisms during crises (55). Women's caregiving roles, however, introduce unique stressors, as they are frequently tasked with ensuring family safety and wellbeing during extreme weather events or periods of environmental degradation. These responsibilities can lead to heightened anxiety, emotional distress, and burnout (56). Furthermore, women frequently serve as central figures in disaster response and recovery efforts, both formally and informally, exposing them to trauma and the emotional suffering of others. While this exposure increases their risk of anxiety and depression, it may also enable them to provide emotional support to others, creating a dual role that acts as both a stressor and a protective factor (57).

These findings underscore the complex interplay of gender, societal expectations, and climate-induced stressors in shaping suicide death outcomes. For men, fostering a culture that encourages emotional expression and provides accessible mental health resources may help reduce the risk of suicide deaths. For women, strengthening support networks and addressing the added caregiving and emotional burdens imposed by climate crises are essential for mitigating mental health challenges.

Our analysis of six studies involving 28,466 male and 41,052 female participants revealed a higher prevalence of self-harm among females, 20.5% (95% CI: 20.09–20.87), compared to males, 16.3% (95% CI: 15.85–16.71). This gender difference likely reflects variations in emotional regulation and social expectations. Women, often carrying the dual burdens of caregiving and societal pressures, may internalize climate-induced stressors differently from men, leading to heightened rates of self-harm. In contrast, males, who are more prone to externalizing behaviors under stress, exhibit higher rates of suicide attempts and deaths, indicating a divergence in behavioral responses to similar environmental triggers.

Climate-induced factors, such as extreme heat, play a prominent role in self-harm. Unlike suicidal behaviors, which may be driven by cumulative despair, self-harm is often linked to acute triggers, such as physiological stress and heightened impulsivity during heatwaves (58). Prolonged exposure to high temperatures exacerbates emotional dysregulation and diminishes coping reserves, increasing vulnerability to self-harming acts. These patterns differ from the broader existential despair observed in suicide deaths, where chronic environmental degradation and socioeconomic instability are often primary drivers (59). Rapid weather changes, including abrupt temperature shifts or prolonged rainfall, disrupt daily routines and intensify feelings of instability. For individuals with pre-existing mental health conditions, this instability amplifies psychological distress, triggering self-harm behaviors. Unlike suicide attempts, which often reflect a direct response to acute crises, self-harm can arise from persistent emotional dysregulation fostered by unpredictable climate patterns (60). Seasonal patterns further illuminate the distinct relationship between self-harm and climate change. Seasonal affective disorder (SAD), linked to reduced sunlight in winter, is associated with depressive episodes that elevate self-harm risk (61). As climate change alters seasonal cycles, the severity and timing of SAD-related self-harm may intensify, marking a divergence from other suicide-related outcomes that are less influenced by seasonal variability (62). This highlights the need for context-specific mental health interventions that address seasonal impacts.

In summary, self-harm represents a unique behavioral response to climate stressors, distinct from suicidal ideation, attempts, and deaths in its etiology and manifestation. While self-harm often serves as a maladaptive coping strategy for managing emotional distress, its prevalence and triggers differ significantly across genders and environmental contexts.

The inclusion of anxiety in this analysis reflects its critical role in understanding the full spectrum of climate change's impact on mental health. Unlike suicide-related outcomes, which are often the culmination of extreme psychological distress, anxiety represents an early and pervasive response to environmental stressors. By addressing anxiety as a distinct yet interconnected mental health outcome, this study highlights its significance as both a standalone condition and a precursor to more severe outcomes, such as suicidal ideation and attempts. This approach ensures a comprehensive examination of climate change's multifaceted effects on mental wellbeing.

The analysis, incorporating data from 12 studies with 70,978 male and 77,270 female participants, reveals a higher prevalence of anxiety among females (34.2%; 95% CI: 33.83–34.49) compared to males (29.8%; 95% CI: 29.43–30.11). This gender disparity aligns with existing literature suggesting that women, who often bear greater caregiving responsibilities and face heightened socio-economic vulnerabilities, are disproportionately affected by climate-related stressors (63). These findings underscore the importance of addressing gender-specific dynamics in mental health responses to climate change.

Anxiety's relationship with climate change is mediated by various pathways. Extreme weather events, such as hurricanes, floods, and wildfires, trigger immediate psychological responses, including fear and heightened alertness, which can persist as chronic anxiety about future occurrences. This sustained hypervigilance, often referred to as “disaster anxiety,” can escalate into generalized anxiety disorder if unaddressed (64). Additionally, temperature extremes exacerbate anxiety symptoms, with high temperatures contributing to physical discomfort and health issues like dehydration, while low temperatures increase isolation and reduce social interaction, both of which amplify psychological distress (65). “Eco-anxiety,” a term describing chronic anxiety about environmental degradation, further exemplifies the profound impact of climate change on mental health (66). This condition manifests as persistent worry about the planet's future, driven by witnessing environmental destruction and the perceived inadequacy of responses to climate challenges (67). For individuals with strong connections to nature, the degradation of natural environments represents a profound emotional loss, intensifying feelings of helplessness and despair. This unique form of anxiety, while distinct, often intersects with broader mental health outcomes by eroding resilience and increasing vulnerability to severe psychological conditions.

Social and economic disruptions caused by climate change, such as rising sea levels, agricultural failures, and competition for resources, further exacerbate anxiety levels. Vulnerable populations, particularly those in poverty or with limited access to resources, are disproportionately affected, experiencing heightened uncertainty and chronic stress (68). These socio-economic stressors not only amplify anxiety but also create conditions that may lead to more severe outcomes, such as suicidal ideation or attempts (69).

By contextualizing anxiety within the broader framework of climate change-induced mental health outcomes, this analysis emphasizes its interconnectedness with suicide-related behaviors. Anxiety often serves as a gateway condition, with chronic, unmanaged distress potentially escalating to self-harm or suicide in vulnerable individuals. Addressing anxiety at this early stage offers an opportunity to intervene and mitigate progression to more severe psychological outcomes, reinforcing the importance of including anxiety as a critical focus in climate-related mental health research and interventions.

Addressing the mental health impacts of climate change requires a comprehensive approach, integrating prevention and intervention strategies to mitigate the associated risks of suicidal ideation, suicide attempts, suicide deaths, self-harm, and anxiety. Early identification and regular screening of at-risk populations are essential. Healthcare providers should employ standardized screening tools during routine medical visits and community health programs to detect early signs of mental health issues (70). Ensuring accessible mental health services, especially in regions most affected by climate change, is critical. Telemedicine can extend the reach of counseling and psychiatric care to remote or underserved areas, offering timely support (71). Strengthening community resilience through social cohesion programs and mutual support initiatives, such as peer support groups and mental health workshops, can significantly aid individuals in coping with climate-induced psychological stressors (72). Public education campaigns are necessary to raise awareness about the mental health impacts of climate change and the importance of seeking help. These campaigns should aim to destigmatize mental health issues and encourage proactive management. Integrating mental health considerations into climate policies and disaster response plans ensures that mental health services are included in emergency relief and long-term recovery efforts (73). Healthcare providers require specialized training to address the mental health impacts of climate change effectively. This training should cover trauma-informed care and the specific needs of climate-affected populations. Gender-specific interventions are also crucial, as women and men experience different mental health impacts from climate change. Support programs tailored to these needs can significantly reduce the rates of anxiety, self-harm, and suicidal behavior. Providing economic support and reducing social vulnerabilities can alleviate the stress exacerbated by climate change, thus mitigating mental health crises. Policies that offer financial assistance, job security, and housing stability are essential (17, 74, 75). Engaging communities in environmental stewardship activities can enhance mental wellbeing by fostering a sense of purpose and connection (76). Lastly, developing robust crisis intervention strategies, including hotlines, mobile crisis units, and rapid response teams, ensures immediate support during climate-related emergencies (77).