The current research’s target population was the general adult population over the age of 18 residing in Portugal. The lack of a database for this population meant the research team had to conduct a non-probabilistic survey to collect primary data. A combination of convenience and snowball sampling methods was applied to locate residents in Portugal who were either quarantined or self-isolated at home.

A pre-test of the questionnaire was conducted in the last week of March 2020 to collect comments and feedback about the questionnaire from a sample of ten residents living in the Algarve region, who were not included in the main survey. An invitation to take the survey was sent to potential participants by email. The pre-test respondents were asked not only to answer the survey but also to make comments on the survey’s content and structure. Based on the results, the questionnaire’s introduction was clarified, and ambiguous wording in a couple of questions was rewritten. This study’s design was reviewed and approved by the University of Algarve’s Research Ethics Committee (i.e. ref. 005/2020).

To approach residents in Portugal more effectively and extensively, the questionnaire was sent individually to acquaintances through the researchers’ social networks and published on the Science4COVID-19 website (see This website is an initiative of the Portuguese Foundation for Science and Technology and the Agency for Clinical Research and Biomedical Innovation, which was launched 3 April 2020, in partnership with public and private health authorities and scientific research institutions. The website’s goal is to mobilise scientific communities to conduct joint research and development projects and activities aimed at combating COVID-19.

The online survey was conducted from 29 March to 19 April 2020, and a total of 904 valid, completed questionnaires were obtained. Since the sample did not match the target population’s profile in terms of gender, age and education, the data were weighted according to these variables to increase the results’ representativeness for adults residing in Portugal. Data from the Portuguese census [37] were used to compute the weights and compensate for overrepresented and underrepresented subpopulations in the sample as defined by gender, age and education.

To facilitate a comparison with Portugal’s pre-COVID-19 pandemic general population, the dataset also included information on all the individuals in a representative random sample of adult Portuguese, which was stratified by gender, age and region. This sample of 1006 individuals was surveyed between November 2015 and January 2016. Further details of the previous study’s methodology can be found elsewhere [38].