**2. Materials and Methods**

### *2.1. Participants*

A total sample of 492 participants was included in the study. Of the total sample, 27.0% were male, and the ages ranged from 18 to 24 (M = 21.06, SD = 1.82). According to the hypothesis of our study, the sample was divided into two groups: those who experienced COVID-19 symptoms (CE) and those who did not experience COVID-19 symptoms (NCE). The CE sample included 211 participants (18–24 years old; M = 21.07, SD = 1.80), and 21.8% were male. The NCE sample included 281 participants (18–24 years old; M = 21.05, SD = 1.84), and 31.0% were male. With respect to the CE sample, 85.8% of the participants were university students, 3.3% were secondary school students, 7.6% were workers, and 3.3% were unemployed. With regard to the item "Who contracted COVID-19," 20.9% stated "him/herself," 14.7% stated "household members," and 64.5% stated "relatives or close friends." The full sociodemographic characteristics are described in Table 1.


**Table 1.** Demographic characteristics of the studied population.

CE = individuals with COVID-19 symptoms experience; NCE = individuals without COVID-19 experiences.

#### *2.2. Procedures*

We collected data throughout the Qualtrics Platform online survey. This study was launched on 18 December 2020 and concluded on 5 February 2021. The survey was diffused on social networks and the university's official website. Participants agreed to participate by signing a digital informed consent form and were informed that the data collection was anonymous and data were not shared outside the current research procedures. After digitally signing the informed consent form, participants were asked to complete the different questionnaires. Demographic characteristics, knowledge, perceptions, and behaviors related to COVID-19 were investigated with ad hoc items; in addition, mood disorders, self-efficacy, and social connectedness were explored. This study was conducted according to the ethical standards of the Helsinki Declaration and was approved by the Institutional Review Board of the Department of Psychology of "Sapienza" University of Rome (protocol number 0002195/18-12-2020).
