Materials and methods - Measures 
Outcome variable  
Thirty-day traumatic stress symptoms (TSS) are defined as a positive screen on the four-
item version (Zuromski et al., 2019) of the PTSD checklist for DSM-5 or PCL-5 (Blevins et 
al., 2015; Weathers et al., 2013) using a cut-off point of seven (Zuromski et al., 2019). The 
official Spanish translation of the PCL-5 scale was provided to us through email by the U.S. 
National Center for PTSD (https://www.ptsd.va.gov/), and coincides with the translation 
available at the official website for Cognitive Processing Therapy for PTSD 
(https://cptforptsd.com/cpt-resources/). This four-item version generates outcomes that closely 
parallel those of the full PCL‐5 (AUC>0.9; Zuromski et al., 2019). We use the more generic 
term “traumatic stress symptoms (TSS)” instead of Acute Stress Disorder (ASD) or Post 
Traumatic Stress Disorder (PTSD), because we did not explicitly determine presence of TSS 
for more than 30-days (criterion F for PTSD according to the DSM-5), and because a short 
screening instrument was used to assess the outcome. 
Description of the four-item version of the PCL-5:  
 Introduction: “Below is a list of problems that people sometimes have in response to a 
very stressful experience. This stressful event can be related to the ongoing COVID-19 
pandemic (for example, severe illness or death of a loved one, intense stress at work, 
having been isolated or in quarantine, …) or can be any other stressful event you once 
experienced. Please read each problem carefully and then indicate how much you have 
been bothered by that problem in the past 30 days”. 
 Response options: “Not at all”, “A little bit”, “Moderately”, “Quite a bit”, “Extremely”.  
 List of traumatic stress symptoms: “Suddenly feeling or acting as if the stressful 
experience were actually happening again (as if you were actually back there reliving 
it)?”, “Avoiding external reminders of the stressful experience (for example, people, 
places, conversations, activities, objects, or situations)?”, “Feeling distant or cut off 
from other people?”, “Irritable behavior, angry outbursts, or acting aggressively?” 
Given concerns regarding the unknown discriminative validity of the PCL-5 versus general 
negative emotionality such as depression and anxiety (Bridgland et al. 2021) and given the high 
degree of co-morbidity between TSS/PTSD and other mental disorders (Bryant, 2018), we 
conducted analyses investigating associations between pandemic-related stressful experiences 
and TSS, additionally adjusting for co-occurring depression and anxiety. Depression and 
anxiety were assessed using the Patient Health Questionnaire (PHQ-8; Kroenke et al 2008) 
and the Generalized Anxiety Disorder scale (GAD-7; Spitzer et al. 2006). 
Distal (pre-pandemic) risk factors 
We considered eleven distal (i.e., pre-pandemic) risk factors, assessed in the T1 survey. Age 
was assessed as a continuous variable and subsequently recategorized into 3 categories, i.e., 
18-29/30-49/50-64/65< years for analysis. Gender was categorized as “female” and “male”. 
Country of birth was assessed using a dropdown list including all countries, and subsequently 
recategorized into “Spain” and “other” for analysis. Marital status was assessed with response 
options “single”, “divorced or legally separated”, “widowed”, and “married”, and 
subsequently recategorized into “married”, and “single, divorced, separated, or widowed” for 
analysis. Pre-pandemic monthly income was assessed using response options “below 570€” 
/ “570-799€” / “800-1,049€” / “1,050-1,299€” / “1,300-1,549€” / “1,550-1,799€” / “1,800-
2,199€” / “2,200-2,699€” / “2,700-3,599€” / “3,600-4,499€” / “4,500-5,999€” / “over 6,000€”, 
and subsequently recategorized into “below 2,200€”, “2,200-4,500€”, and “over 4,500€”. 
Having children in care was assessed as a dichotomy (no / yes). Type of profession was 
assessed as a checklist and subsequently recategorized into five groups for analysis: medical 
doctor; (2) nurse; (3) auxiliary nurse; (4) other profession involved in patient care (i.e., 
midwife, dentist or odontologist, pharmaceutical, laboratory, or radiology technician, 
psychologist, physiotherapist, social worker, patient transport); and (5) other profession not 
involved in patient care (i.e., administrative and management personnel, logistic support, 
research‐only personnel). Type of workplace was assessed as a checklist and subsequently 
categorized into four groups for analysis: (1) Emergency Department (ED) of a hospital, (2) 
Hospital (other than ED), (3) primary care, and (4) others (e.g., pharmacy, public health service, 
institution for people with disabilities). Number of pre-pandemic lifetime mental disorders 
was assessed using Composite International Diagnostic Interview (CIDI) 3·0 adapted screener 
items (Kessler & Üstün, 2004) including mood (i.e., depressive and bipolar disorders), anxiety 
(i.e., panic, generalized anxiety and obsessive-compulsive disorders), substance use (i.e., 
alcohol, illicit drugs, and prescription drugs with or without prescription), and other disorders. 
A sum score was created and categorized into “none”, “exactly one”, and “two or more”. 
Number of pre-pandemic physical health conditions was assessed using a 7-item checklist 
(Sangha et al. 2003) including respiratory diseases (not provoked by coronavirus), 
cardiovascular diseases, diabetes, cancer, chronic hepatic diseases, immunological diseases, 
and “other”. A sum score was created and categorized into “none”, “exactly one”, and “two or 
more”. Twelve-month physical or sexual assault was assessed as a dichotomy (no / yes). 
Proximal risk factors (pandemic-related stressful experiences) 
Four domains of pandemic-related stressful experiences were assessed in the T1 survey, using 
as time frame the onset of the virus outbreak in Spain. A first domain considered three 
COVID-19 infection-related stressful experiences: (1) personal COVID-19 infection 
status was categorized into “having been hospitalized for COVID-19”, “positive COVID-19 
test or medical COVID-19 diagnosis without hospitalization”, and “never infected with 
COVID-19”; (2) having loved ones infected with COVID‐19 was categorized into “no loved 
ones infected”, “partner, children, or parents infected”, “other family, friends or others 
infected”; and (3) having been in isolation or quarantine because of COVID‐19 was 
assessed as a dichotomy (no/yes). 
The second domain included eight work-related stressful experiences: (1) average weekly 
hours worked was assessed as a continuous variable an subsequently categorized into “40 
hours or less”, “41-50 hours”, and “51 hours or more” for analysis; (2) changes in assigned 
functions, team, or working location was categorized into “no changes”, “having changed of 
team or assigned functions (but not having changed to a specific COVID‐19‐related work 
location)”, and “having changed to a specific COVID‐19‐related work location (e.g., 
emergency room, COVID ward, fever clinic, intensive care unit, quarantine center, field 
hospital)”; (3) perceived lack of training for assigned tasks was assessed using a 5-level 
Likert-type scale ranging from “none of the time” to “all of the time”; (4) the frequency of 
direct exposure to COVID-19 patients during professional activity was assessed using a 5-
level Likert-type scale ranging from “none of the time” to “all of the time”; (5) the perceived 
lack of healthcare center preparedness was assessed four five-level Likert type scales that 
assessed lack of coordination, communication, personnel, and supervision at work, respectively 
(Cronbach α= 0.86). Each scale had response options from “none of the time” to “all of the 
time”. Items were summed and rescaled to a 0–4 summary scale score; (6) perceived 
frequency of lack of protective equipment was assessed using a 5-level Likert-type scale 
ranging from “none of the time” to “all of the time”; (7) having to make decisions regarding 
prioritizing care among COVID‐19 patients was assessed as a dichotomy (no/yes) among 
medical doctors and nurses; and (8) having patient(s) in care that died from COVID‐19 was 
assessed as a dichotomy (no/yes) among all HCW involved in patient care. 
A third domain consisted of six variables that measured health-related stress using five-
level Likert type scales: (1) feeling of little control over getting infected or not was assessed 
using a 5-level Likert-type scale ranging from “none of the time” to “all of the time”; (2) fear 
of infecting loved ones was assessed using a 5-level Likert-type scale ranging from “none of 
the time” to “all of the time”; (3) family and friends degree of worry of getting infected 
through the HCW was assessed using a 5-level Likert-type scale ranging from “none of the 
time” to “all of the time”; (4) degree to which people avoided the HCW’s family because of 
the HCW’s job was assessed using a 5-level Likert-type scale ranging from “none of the time” 
to “all of the time”; (5) personal health-related stress was assessed using two 5-level Likert-
type scales (concern about the respondent possibly being infected with COVID 19, concern 
about own respondents’ health in general; Cronbach α= 0.80). Items were summed and rescaled 
to a 0–4 scale score; and (6) stress related to the health of loved ones was assessed using two 
5-level Likert-type scales (concern about loved ones being infected with COVID 19, concerns 
about the health of loved ones; Cronbach α= 0.85). Items were summed and rescaled to a 0–4 
scale score. 
A fourth domain consisted of two financial stressful experiences: (1) having suffered a 
significant loss in personal or family income due to the COVID‐19 pandemic was assessed 
as a dichotomy (no/yes); and (2) stress over one's financial situation was assessed using two 
5-level Likert-type scales (financial stress, stress related to loss of job or income due to 
COVID-19; Cronbach α= 0.82). Items were summed and rescaled to a 0–4 scale score. 
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