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

country. Currently, we do not have a comprehensive estimate of the distribution and preva- lence of the mental health impacts of climate change in Canada, and little evidence is available globally. Therefore, our team has developed a protocol for a nationally representative cross- sectional survey to estimate the prevalence, magnitude, and distribution of mental health chal- lenges connected to climate change in Canada. Herein, we describe the protocol for data col- lection, processing, and analysis. Although this protocol has been developed for use in Canada, the study design and methods aim to overcome common challenges and limitations in this field of research, and our call for epidemiological rigour in climate-mental health survey design is applicable globally. Methods Primary objectives The overall goal of the study is to estimate the prevalence of a variety of emotional responses and subclinical mental health outcomes that disrupt or impair normal functioning as they relate to climate change (Table 1). Specifically, the primary objective is to estimate the preva- lence of climate-related emotions and subclinical outcomes by province/territory, by month, and by age group (i.e. 13–34 years; 35–54 years; 55–74 years; 75+ years old). Secondary objec- tives include examining the association of subclinical outcomes with various socio-demo- graphic variables (e.g. age, gender, income, and other identities), direct or vicarious experiences of past or current climate change impacts, anticipation of future climate change

impacts, and behavioural responses to climate-related stressors. Design This population-based cross-sectional survey (i.e. prevalence study) of youth and adults aged 13 years and older in Canada will be administered over the course of one year (12 months). The protocol was developed by an interdisciplinary team of researchers in Canada and the USA with expertise spanning mental health, climate change, psychology, epidemiology, social sciences, health geography, economics, and public health. The survey was administered by R. A. Malatest & Associates Ltd. (Malatest), one of Canada’s largest independently owned and operated research and evaluation firms. Survey recruitment commenced on April 1, 2022, and data collection is expected to continue through to March 31, 2023. Climate change and mental health scales and theory Climate change anxiety is a psychological phenomenon that has gained prominence in recent years. Clayton and Karaszia (2020) developed and validated a scale that quantifies the extent to which individuals experience anxiety related to climate change [33]. Their analysis found that Table 1. A summary of research questions related to our primary survey objective. Primary Research Question Example Question RQ1 What is the prevalence of climate-related emotions and subclinical outcomes in Canada? RQ2 What is the prevalence of climate-related emotions and subclinical outcomes in each province/territory in Canada? RQ3 What is the prevalence of climate-related emotions and subclinical outcomes in Canada each month?

RQ4 What is the prevalence of climate-related emotions and subclinical outcomes in Canada by age group? https://doi.org/10.1371/journal.pone.0291303.t001 PLOS ONE Climate change and mental health survey protocol PLOS ONE | https://doi.org/10.1371/journal.pone.0291303 October 11, 2023 3 / 12