*2.2. Participants and Procedure*

Data were collected during the period of 20–31 March, 2020. Participants were recruited online through an invitation posted on social media (Facebook and WhatsApp). This approach of online recruitment was selected primarily due to the lockdown situation, which prevented us from collecting data in the laboratory. According to the aim of the study, it was necessary for us to capture the psychological state of participants at the time of the pandemic; thus an a posteriori study would not have provided useful and reliable information.

Participants were invited to complete an anonymous online questionnaire to report their personal experiences with the COVID-19 emergency and their mental state. The inclusion criteria were the following: (a) living in Italy at the time of data collection and (b) being aged 18+ years (18 years is the legal age in Italy, defined by the capacity to act and be emancipated). Participation was voluntary. All participants were required to read and provide informed consent before beginning the online questionnaire. They received no compensation for their participation. In total, 2072 volunteers took part in the study. Of these, 19 were excluded on the basis that they responded to the questionnaire twice (we kept only their first response). Thus, the final sample was comprised of 2053 participants, of whom 1555 were female, 480 were male, and 18 were reported as "other." The participants' average age was 35.81 (*SD* = 13.19; range: 18–83) and their average education level was 15.35 years (*SD* = 3.43; range: 5–21). A more detailed description of the sample's demographic characteristics is provided in the Supplementary Materials. It has been calculated that a sample size of 2053 is sufficiently large to achieve at least a statistical power (1-β) = 0.90 in a linear multivariable regression analysis involving 18 predictors, given a significance level α = 0.05 and an effect size of 0.356 [65]. Data are provided in the Supplementary Materials.
