Estimating climate change and mental health impacts in Canada: A cross-sectional survey protocol

drought, extreme heat waves, storms) has been associated with both diagnosable mental disor- ders and subclinical outcomes that disrupt or impair normal functioning [1]. Indirectly or vicariously experiencing climate change (e.g. witnessing climate change impacts on the news, seeing climate change affect friends and family, learning about climate change impacts and (in)actions) or anticipating future climate change risks can also lead to mental health chal- lenges [1]. Given these widespread and complex etiological pathways, climate change is increasingly recognized as a grand and urgent challenge for mental health [1–5]. Although we know that climate change has complex, serious, and diverse impacts on men- tal health, the frequency, magnitude, and distribution of those impacts is less clear. To date, cli- mate change and mental health research has been predominantly quantitative in nature [6– 11], and most often examines mental health after a major climate hazard or disaster [6, 9, 12]. For example, many studies have examined hospital admissions for mental health conditions or suicide following extreme heat waves [13, 14], droughts [15], floods [10, 16, 17], and wildfires [18]. Due to the acute nature of these climate events, the association with excess mental health morbidity and mortality is clear and often striking. However, studies that examine mental health impacts outside of extreme events are less common [6, 9]. Further, previous studies that explored climate change impacts on psychoso-

cial wellbeing have primarily relied on surveys using non-probability sampling with university students and have often used crowdsourcing (e.g. Amazon MTurk) to source participants [19]. Both of these methods can create study-entry selection bias due to non-random sample selec- tion [20], particularly coverage bias and self-selection bias [21], which can result in a study sample that does not represent the target population and compromises the external validity of results. New climate and mental health survey literature seeks to address these potential biases by deploying systematically inclusive national surveys that aim to provide every member of the population with an equal chance of being included [22]. There is also a small but growing body of qualitative research exploring climate change impacts on psychosocial wellbeing. Qualitative research has provided insights into the diverse pathways and mechanisms through which climate change affects mental health [23, 24]. For example, in-depth, predominantly qualitative research has illustrated how climate change has led to ecological grief for Inuit in Arctic Canada and for farmers in the Australian Wheatbelt [25]. A growing number of qualitative studies have also documented experiences of solastalgia, or the pain caused by negative environmental changes to one’s home [26], especially among people in the United States and Australia [27]. Although these studies provide detailed insights into the ways in which climate change affects mental health, they do not provide comprehen-

sive data on how common these climate-mental health experiences are in the general population. Canada is a global leader in advancing our understanding of climate change impacts on mental health. Indeed, a relatively large proportion of published research on this topic has come from Canada [6, 7, 28], particularly qualitative studies [6]. Evidence on the mental health implications of climate change is beginning to inform policy, programs, and decision-making in Canada. For example, mental health has been included—for the first time—in Canada’s national climate change assessments [e.g. 3, 29, 30], in Canada’s first National Adaptation Strategy [31], and in the Chief Public Health Officer’s 2022 annual report [32]. The available evidence clearly suggests that climate change has substantial implications for mental health, and there is increasing recognition of the importance of these impacts in policy decision-making in Canada. However, when sharing this research evidence with decision- makers, policy-makers, and the general public, our research team is often asked about the national prevalence and distribution of climate change impacts on mental health, and about the diverse pathways through which climate change negatively affects mental health across the PLOS ONE Climate change and mental health survey protocol PLOS ONE | https://doi.org/10.1371/journal.pone.0291303 October 11, 2023 2 / 12 Funding: Funding support was provided by the Canadian Institutes for Health Research (to Harper and Cunsolo), ArcticNet (to Cunsolo), Social

Science and Humanities Research Council Doctoral Fellowship (to Aylward), Izaak Walton Killam Memorial Scholarship (to Aylward), and Alberta Innovates Graduate Student Scholarship (to Aylward). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist.