*2.3. Variables and Instruments*

Sociodemographic variables were collected, including age, gender, place of residence (rural/urban), course, chronic diseases, number of cohabitants during confinement and smoking habits.

A series of COVID-19 variables were also considered (questions with yes/no responses): Have you had COVID-19? Has anyone in your close environment suffered from the virus? Has anyone in your close environment died from COVID-19?

Having suffered from the disease was considered the dependent variable (DV). The following independent variables were collected:

• Sense of coherence was evaluated using the Orientation to Life Questionnaire— 13 Items (OLQ-13 or SOC-13) [15]. This instrument measures a global personality orientation that facilitates adaptive problem solving in stressful situations. The 13-item questionnaire also measures the dimensions of understandability (5 items), manageability (4 items) and meaningfulness (4 items). The scores express the strength of the person's SOC; the higher the score, the greater the strength. The answers offer a continuum of degree from minus to plus in 7 response options on a Likert scale from 1 to 7 ("never" "rarely" to "very often" or "always"), both in the positive and negative dimensions of the question. The OLQ-13 scale presents suitable internal consistency, with a Cronbach's alpha between 0.70 and 0.92 [16,17], and retains the same psychometric qualities as the original 29-item version. In this study, the internal consistency of the items was analyzed using Cronbach's alpha for the total scale (0.71) and for the comprehensibility (0.81), manageability (0.79) and significance (0.71) subscales.

For the assessment of risk perception, perceived risk factors and coping styles in the face of COVID-19, an ad hoc survey was designed by a panel of 6 experts based on the literature [18–20]. This survey, called the Perception. Risk. Coping. Knowledge (PRCK-COVID-19) scale, was created and validated because there was no specific survey for young people adapted to the pandemic situation of COVID-19. It was validated on a sample of 30 students, with adequate psychometric properties. The scales have been validated, piloted and created for the Spanish population. This survey consists of four scales:

• Perceived risk scale (3 items). The degree of agreement was shown on an LS (0, none and 10, maximum risk). The maximum score is 30 points, indicating that the higher the score, the higher the perceived risk of COVID-19 infection. Factor analysis identified a one-factor structure (Cronbach's alpha = 0.735).

