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

and younger age groups). If the subpopulation is small, targeted social media advertisements may be used to increase awareness of the survey (but note that these advertisements will not be used to facilitate recruitment). Quotas for certain demographic characteristics can be set each month; that is, once a quota has been met for a demographic group, the questionnaire will not be available for participants belonging to that group for the remainder of the month. Finally, to help reach our demographic quotas, we could limit or remove the ability for certain demo- graphics to be recruited over the telephone (i.e. those in a certain age group are not eligible to be recruited via telephone). Ethics All participants will be provided with an information letter that outlined the study details. We will obtain informed consent from all participants: telephone participants provided informed consent orally (documented by the surveyor) and online participants provided informed con- sent electronically. We were granted a waiver of parental/guardian consent for participants between the ages of 13–18, given that our study met all criteria under Article 3.7 of the TCPS2. Our study is an anonymous survey that collects minimal identifying information and involves minimal risk to participants. The study protocol was approved by the ethics research boards at the University of Alberta and Memorial University of Newfoundland and Labrador. A research licence was obtained from the Nunavut Research Institute. Data processing and analyses

The questionnaire response data will be downloaded in English (all responses to open-ended questions in languages other than English will be translated into English by Malatest and then provided to the research team) into Excel (Microsoft Corporation, Redmond, WA), and then uploaded into Stata (StataCorp LLC, College Station, TX) and R (The R Foundation, Indianap- olis, IN) for analysis. Data will be population-weighted (e.g. by age, province/territory, gender, Table 3. A summary of the target number of responses by province/territory and age group for the entire survey period (1 year). Target Number of Respondents by Age Groups Provinces/Territories 13–34 years 35–54 years 55–74 years 75+ years Total* Alberta 100 97 72 20 289 British Columbia 91 87 84 27 289 Manitoba 103 86 76 24 289 New Brunswick 80 83 96 30 289 Newfoundland and Labrador 77 84 99 29 289 Northwest Territories 112 98 70 9 289 Nova Scotia 86 81 93 29 289 Nunavut 144 97 43 5 289 Ontario 97 86 80 26 289 Prince Edward Island 94 81 87 27 289 Quebec 86 87 87 29 289 Saskatchewan 99 88 77 25 289 Yukon 95 99 81 14 289 Total* 1,214 1,135 1,068 340 3,757 *Target number of respondents were calculated to be proportional to the age demographics of that province or territory using data from Statistics Canada (2021) [48] and may differ from the cumulative sums of each column due to rounding. https://doi.org/10.1371/journal.pone.0291303.t003 PLOS ONE Climate change and mental health survey protocol

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