Psychological impact of the COVID-19 pandemic on out-of-hospital health professionals: A living systematic review

Journal of Clinical Medicine Review Psychological Impact of the COVID-19 Pandemic on Out-of-Hospital Health Professionals: A Living Systematic Review Raúl Soto-Cámara 1,2 , NoemíGarcía-Santa-Basilia 2,*, Henar Onrubia-Baticón2, Rosa M. Cárdaba-García2,3,* , JoséJulio Jiménez-Alegre 4, Ana María Reques-Marugán2, María Molina-Oliva 2, Juan JoséFernández-Domínguez 4, María Paz Matellán-Hernández 2, Almudena Morales-Sanchez 2 and Susana Navalpotro-Pascual 4   Citation: Soto-Cámara, R.; García- Santa-Basilia, N.; Onrubia-Baticón, H.; Cárdaba-García, R.M.; Jiménez-Alegre, J.J.; Reques-Marugán, A.M.; Molina- Oliva, M.; Fernández-Domínguez, J.J.; Matellán-Hernández, M.P.; Morales- Sanchez, A.; et al. Psychological Impact of the COVID-19 Pandemic on Out-of-Hospital Health Professionals: A Living Systematic Review. J. Clin. Med. 2021,10, 5578. https:// doi.org/10.3390/jcm10235578 Academic Editor: Serge Brand Received: 31 October 2021 Accepted: 24 November 2021 Published: 27 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1Department of Health Sciences, University of Burgos, 09001 Burgos, Spain; [email protected] 2Emergency Medical Service of Castilla y León—Sacyl, 47007 Valladolid, Spain; [email protected] (H.O.-B.); amr[email protected] (A.M.R.-M.); [email protected] (M.M.-O.); [email protected] (M.P.M.-H.); [email protected] (A.M.-S.) 3Nursing Department, Faculty of Nursing, University of Valladolid, 47005 Valladolid, Spain 4Emergency Medical Service of Madrid—SUMMA 112, 28045 Madrid, Spain; [email protected] (J.J.J.-A.); [email protected] (J.J.F.-D.); [email protected] (S.N.-P.) *Correspondence: [email protected] (N.G.-S.-B.); rosamaria.car[email protected] (R.M.C.-G.) Abstract: Health professionals (HPs), especially those working in the front line, have been one of the groups most affected by the COVID-19 pandemic. The objective of this study is to identify the best available scientific evidence on the impact of the COVID-19 pandemic on the mental health of out-of-hospital HPs in terms of stress, anxiety, depression, and self-efficacy. A living systematic review of the literature was designed, consulting the electronic online versions of the CINHAL, Cochrane Library, Cuiden, IBECS, JBI, LILACS, Medline PyscoDoc, PsycoINFO, Scopus, and Web of Science databases in November 2021. Original research was selected, published in either English, Spanish, French, Italian, or Portuguese. In total, 2082 publications were identified, of which 16 were included in this review. The mental health of out-of-hospital HPs was affected. Being a woman or having direct contact with patients showing suspicious signs of COVID-19 or confirmed cases were the factors related to a greater risk of developing high levels of stress and anxiety; in the case of depressive symptoms, it was having a clinical history of illnesses that could weaken their defenses against infection. Stopping unpleasant emotions and thoughts was the coping strategy most frequently used by these HPs. Keywords: COVID-19; pandemic; health professionals; out-of-hospital; mental health; anxiety; depression; stress; self-efficacy 1. Introduction In December 2019, the Chinese health authorities reported the presence of new cases of atypical pneumonia of non-identified etiology in Wuhan (Hubei, China) [ 1 ]. Subsequently, it was confirmed that the causal pathogenic agent was a new betacoronavirus (RNA), sharing phylogenetic similarities with SARS-CoV-1 [ 2 , 3 ], for which reason it was labeled as SARS-CoV-2. Viral transmission between people principally occurs through the air, although on some occasions, it is through conjunctival, nasal, or buccal mucosa and feces [4]. The rapid propagation of cases between continents, together with community transmission in different countries, led the World Health Organization (WHO) to declare the illness caused by the COVID-19 virus as “The Sixth Public Health Emergency of J. Clin. Med. 2021,10, 5578. https://doi.org/10.3390/jcm10235578 https://www.mdpi.com/journal/jcm J. Clin. Med. 2021,10, 5578 2 of 32 International Concern”, proclaiming a pandemic situation on 11 March 2020, with over 118,000 cases confirmed in 114 countries and 4291 deaths [5,6]. This situation had important repercussions, to a greater or lesser extent, at economic, social, and health-care levels within all the countries that were affected. At an economic level, there was a significant reduction in industrial productivity, a considerable loss in the number of employees, a fall in fuel prices, the interruption of supply and distribution chains, multiple firm closures in different sectors, and a substantial increase in expenditure on health materials, all of which were framed within volatile and unstable scenarios [ 7 – 9 ]. At a social level, as well as the increased poverty arising from the economic changes that were taking place, significant governmental restrictions on the general population were imposed in most countries for the purpose of avoiding or minimizing the spread of the virus. Some of these measures were based on the reduction of mobility and interpersonal interaction, such as strict home confinement and social distancing, whereas others were based on the acquisition of new hygienic habits, such as washing hands or the obligatory use of facemasks [ 10 – 12 ]. At the health-care level, the health systems in all countries had to adapt their organization and functioning to the new epidemiological situation in existence. As a consequence, health professionals (HPs) were subjected to high workloads over long working days, considerably reducing their hours of rest, with a lack of approved individual protective equipment and with no clear and defined protocols for action; all of these circumstances increased their risk of infection [ 13 – 15 ]. Continuous exposure to this new situation, together with the fear of infecting family members and isolation or social discrimination that they suffered on many occasions, could affect the exercise of their professional functions, considerably reducing their attention span, understanding, and decision-making capabilities [ 13 , 16 , 17 ]. Despite the above, a study conducted in Singapore showed that the recovery of spontaneous circulation in patients in cardio-respiratory arrest was not lower than before the pandemic [ 18 ]. However, some HPs, especially those in the front line, saw that their general well-being had been altered, and they started to show signs of physical and mental exhaustion, high levels of anxiety and depression, other emotional disorders, dysfunctional cognitive reactions, sleep problems, difficulty in interpersonal relations, substances use behaviors, and even post-traumatic stress [ 19 – 23 ]. In this sense, some studies have concluded that nurses entering into direct contact with COVID-19-infected patients have been the HPs at most risk of developing these adverse results during the pandemic [24] (Figure 1). J. Clin. Med. 2021, 10, x FOR PEER REVIEW 2 of 31 This situation had important repercussions, to a greater or lesser extent, at economic, social, and health-care levels within all the countries that were affected. At an economic level, there was a significant reduction in industrial productivity, a considerable loss in the number of employees, a fall in fuel prices, the interruption of supply and distribution chains, multiple firm closures in different sectors, and a substantial increase in expenditure on health materials, all of which were framed within volatile and unstable scenarios [7–9]. At a social level, as well as the increased poverty arising from the economic changes that were taking place, significant governmental restrictions on the general population were imposed in most countries for the purpose of avoiding or minimizing the spread of the virus. Some of these measures were based on the reduction of mobility and interpersonal interaction, such as strict home confinement and social distancing, whereas others were based on the acquisition of new hygienic habits, such as washing hands or the obligatory use of facemasks [10–12]. At the health-care level, the health systems in all countries had to adapt their organization and functioning to the new epidemiological situation in existence. As a consequence, health professionals (HPs) were subjected to high workloads over long working days, considerably reducing their hours of rest, with a lack of approved individual protective equipment and with no clear and defined protocols for action; all of these circumstances increased their risk of infection [13– 15]. Continuous exposure to this new situation, together with the fear of infecting family members and isolation or social discrimination that they suffered on many occasions, could affect the exercise of their professional functions, considerably reducing their attention span, understanding, and decision-making capabilities [13,16,17]. Despite the above, a study conducted in Singapore showed that the recovery of spontaneous circulation in patients in cardio-respiratory arrest was not lower than before the pandemic [18]. However, some HPs, especially those in the front line, saw that their general wellbeing had been altered, and they started to show signs of physical and mental exhaustion, high levels of anxiety and depression, other emotional disorders, dysfunctional cognitive reactions, sleep problems, difficulty in interpersonal relations, substances use behaviors, and even post-traumatic stress [19–23]. In this sense, some studies have concluded that nurses entering into direct contact with COVID-19-infected patients have been the HPs at most risk of developing these adverse results during the pandemic [24] (Figure 1). Figure 1. Diagram of the main repercussions of the COVID-19 pandemic. COVID - 19 pandemic Repercussion at economic level Repercussion at ec onomic level Repercussion at health level Increase in the risk infection of HPs' Impact on the exercise of HPs' functions' HPs with high workloads over long working days  Lack of individual protective equipment and protocols Increased poverty Reduction of mobility and interpersonal interaction Acquisition of new hygienic habits Reduction in the industrial productivity Loss of employees Fall un fuel prices Interruption of supply and distribution chains Firm closures in different sectors  Increase in expen diture on health materials Figure 1. Diagram of the main repercussions of the COVID-19 pandemic. J. Clin. Med. 2021,10, 5578 3 of 32 HPs had to have sufficient levels of self-efficacy and to adopt adequate coping strategies in order to be able to manage this new situation, to avoid the appearance of maladaptive responses, and to reduce the risk of developing post-traumatic stress or other mid-to-long-term associated pathologies [ 25 , 26 ]. According to Bandura, self-efficacy is defined as “the judgments of each individual on his capacity, on the basis of which he will organize and execute his acts in a way that allows them to achieve the desired performance” [ 27 ]. On the other hand, the term coping includes the cognitive and behavioral efforts that the person makes to control, reduce, and tolerate the internal and external demands of a certain situation in which their individual resources are exceeded [ 28 ]. In a general way, stopping unpleasant emotions and thoughts is the most effective coping strategy for the reduction of stress levels and an increase in positive mental states [ 26 ]. However, avoidance behavior is the most widely used strategy, associated with higher levels of stress and the development of post-traumatic symptomology [ 29 – 31 ]. Problem-focused strategies are usually correlated with a lower impact on the mental health of HPs [ 32 , 33 ]. During the COVID-19 pandemic, HPs who adopted passive coping strategies presented higher levels of stress, anxiety, and depression. Moreover, perceived social support and active coping strategies were negatively correlated with these variables, which favored compliance with the security protocols against COVID-19 and the adoption of social-distancing measures [34–36]. Emergency medical service (EMS) is in charge of out-of-hospital care for critically ill patients. To face the COVID-19 pandemic, this service had to develop policies and procedures to address the safe caring of patients with suspected or known COVID-19 and a potential increase in the volume of calls. In some countries with low SARS-CoV-2 transmission rates, such as Singapore, EMS use was largely stable during the social distancing and home confinement period compared to previous figures [ 18 ]. However, in a study conducted in the United States during the first phase of the pandemic, a general decrease in the number of EMS activations was identified, compared to the prior weeks and the same period in previous years, as well as an increase in the rate of EMS-attended deaths [ 37 ]. These results may be due to the fact that patients requiring hospitalization refuse to be transported for fear of being infected by healthcare personnel or other patients. Another study concluded that the decline in EMS use for cardiac arrest, stroke, or time-sensitive illness during the peak of the pandemic was related to patient perception rather than actual case count [ 38 ]. In many cases, the HPs from these EMS were first front-line healthcare providers to patients showing suspicious signs of COVID-19 or who were confirmed cases, making them one of the groups of workers most affected by this pandemic [ 39 ]. The working conditions of EMS HPs have been particularly vulnerable with respect to the hospital workers. The homogeneous diffusion of the aerosols resulting from a patient ´ s cough across the entire ambulance, through the ventilation systems, together with the close contact with the patient for longer periods of time, makes these HPs one of the collectives with the highest risk of contracting this infectious disease [ 39 , 40 ]. Indeed, these patients have been transported to hospitals considerably further away from their place of residence due to frequent closures of hospital wards [ 41 ]. Based on this, several studies have already assessed how these workers can work in the best possible way when facing a pandemic situation. Like HPs in other areas, the main concerns perceived by out-of-hospital workers have been their moderate degree of training and knowledge about COVID-19, the risk of infecting themselves or their family members, and the lack of personal protective equipment [ 41 – 43 ]. These concerns may lead to poorer mental health, resulting in a decreased quality of patient care [44] (Figure 2). Given the framework of references set out above, the objective of this study is to identify the best available scientific evidence on the impact that the COVID-19 pandemic has had on the mental health of out-of-hospital HPs in terms of stress, anxiety, depression, and self-efficacy. J. Clin. Med. 2021,10, 5578 4 of 32 Figure 2. Diagram illustrating the impact of the COVID-19 pandemic on the healthcare system and mental health of front-line HPs. 2. Materials and Methods Following a previously established research protocol, agreed on by the team of researchers, and in accordance with the stipulations presented in the PRISMA declaration (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [ 45 ], a living systematic review of the available scientific literature was designed. To do so, the electronic version of the following databases were consulted in November 2021: Cumulative Index of Nursing and Allied Literature—CINHAL (EBSCOhost, Ipswich, MA, USA), Cochrane Library, Cuiden, Índice Bibliográfico Español en Ciencias de la Salud—IBECS (BVS, Sao Paulo, Brazil), Joanna Briggs Institute—JBI (Ovid, New York, NY, USA), Literatura Latinoamericana y del Caribe en Ciencias de la Salud—LILACS (BVS, Sao Paulo, Brazil), Medline (Pubmed, Bethesda, MD, USA), PyscoDoc (Ovid, New York, NY, USA), PsycINFO (Ovid, New York, NY, USA), Scopus (Elsevier, New York, NY, USA), and Web of Science—WOS (Elsevier, New York, NY, USA). The study protocol has previously been registered at the International Prospective Register of Systematic Reviews PROSPERO, supported by the Centre for Reviews and Dissemination of the University of York, under reference CRD-42021259951. This living systematic review forms part of a broader project, IMPSYCOVID-19 (Impacto Psicológico de la COVID-19), carried out by the RINVEMER (Red de Investigación en Emergencias prehospitalarias) research group, whose objective is to study the stress, anxiety, depression, and self-efficacy among out-of-hospital HPs in Spain. RINVEMER is a multidisciplinary team composed of 23 members working outside the hospital (physicians, nurses, emergency medical technicians, and psychologists). Among them, 11 members were specifically assigned to the development of this living systematic review. The search began with the formulation of the following research question by R.S.C., whose clinical response was possible, in PIO (Population-Intervention-Outcome) format [ 46 ]: “Has the possible exposure to SARS-CoV-2 during the COVID-19 pandemic (I) affected the mental health (O) of HPs providing health care outside the hospital (P)? From it, the Medical Subject Headings (MeSH), the Descriptors in Health Sciences (DeCS), and synonyms-free text adequate to the objective of the study were identified and combined using the Boolean operators AND and OR. In addition, some of them were truncated in order to include all possible word endings. The initial search strategy was the same for all the databases consulted, adapting it to the particularities of each one of them (Table 1). With the aim of identifying other potentially relevant works that had not previously been recovered, a manual inverse search strategy was proposed, reviewing webpages, sources of grey literature (ProQuest Dissertations and Theses Global, and OpenGrey), as well as bibliographic references cited in the selected studies. All the search strategies in use were developed, reproduced, and checked by three different researchers (R.S.C., R.M.C.G., and J. Clin. Med. 2021,10, 5578 5 of 32 S.N.P.) for the purpose of guaranteeing the reliability of the results by comparing those obtained by each of them. Table 1. Search strategy adapted to each of the databases. Database Search Strategy CINHAL (MH “prehospital emergency care” OR “emergency care” OR “emergency system” OR “out of hospital” OR “emergency medical service*”) AND (MH “health care provider” OR “healthcare worker*” OR “health care professional*” OR “health personnel” OR “physician*, primary care” OR doctor* OR physician* OR “medical staff” OR “nursing personnel” OR “registered nurse*” OR “assistant nurse*” OR nurs* OR “nursing staff” OR “emergency paramedic*” OR paramedic* OR “paramedical personnel” OR “healthcare assistant*” OR “healthcare support worker*” OR “emergency medical technician*” OR “allied health personnel”) AND (MH “2019-nCoV infection” OR “2019-nCoV disease” OR “coronavirus disease-19” OR “severe acute respiratory syndrome coronavirus 2” OR “SARS-CoV-2 virus” OR “SARS-CoV-2 infection” OR “COVID-19” OR “SARS-CoV-2”) AND (MH “COVID-19 pandemic” OR pandemic*) AND (MH “mental health” OR angst OR nervousness OR hypervigilance OR anxiousness OR anxiety OR “anxiety disorder*” OR “depressive syndrome” OR melancholia OR “depressive symptom” OR “emotional depression” OR dysthymia OR depressi* OR “depressive disorder*” OR “dysthymic disorder*” OR “acute stress disorder*” OR “life stress” OR “psychologic stress” OR “psychological stressor” OR “stress disorders, traumatic, acute” OR “stress, psychological” OR “self-confidence” OR “self-efficacy") Cochrane Library “emergency medical service*” AND (“health personnel” OR physician* OR “medical staff” OR nurse* OR “nursing staff” OR “emergency medical technician*” OR “allied health personnel”) AND (“COVID-19” OR “SARS-CoV-2”) AND pandemic* AND (“mental health” OR anxiety OR “anxiety disorder*” OR depression OR “depressive disorder*” OR “stress disorder*, traumatic, acute” OR “stress, psychological” OR “self-efficacy”) Cuiden “servicio* medico* de urgencia” AND (“personal de salud” OR medico* OR “cuerpo médico” OR “enfermera* y enfermero*” OR “personal de enfermería” OR “técnico* medio* en salud”) AND (“infección* por coronavirus” OR “virus del SARS”) AND pandemia* AND (“salud mental” OR ansiedad OR depresión OR “trastorno* de estrés traumático agudo” OR “estrés psicológico” OR autoeficacia) [“emergency medical service” AND (“health personnel” OR doctor OR “medical body” OR “female nurse and male nurse” OR “nursing personnel” OR “health auxiliary”) AND (“infection by coronavirus” OR “SARS virus”) AND pandemic AND (“mental health” OR anxiety OR depression OR “traumatic acute stress disorder” OR “psychological stress” OR self-efficacy)] IBECS (tw:((“emergency medical service*” OR “servicio* medico* de urgencia”) AND (“health personnel” OR “personal de salud” OR physician* OR “medical staff” OR medico* OR “cuerpo medico” OR nurse* OR “nursing staff” OR “enfermera* y enfermero*” OR “personal de enfermería” OR “emergency medical technician*” OR “allied health personnel” OR “técnico* medio* en salud”) AND (“COVID-19” OR “SARS-CoV-2” OR “infeccion* por coronavirus” OR “virus del SARS”) AND pandemic* OR pandemia*) AND (“mental health” OR “salud mental” OR anxiety OR “anxiety disorder*” OR ansiedad OR depression OR “depressive disorder*” OR depresión OR “stress disorder*, traumatic, acute” OR “stress, psychological” OR “trastorno* de estrés traumático agudo” OR “estrés psicológico” OR “self-efficacy” OR autoeficacia)] JBI ((prehospital emergency care OR emergency care OR emergency system OR out of hospital OR emergency medical service*) AND (health care provider OR healthcare worker* OR health care professional* OR health personnel OR physician*, primary care OR doctor* OR physician* OR medical staff OR nursing personnel OR registered nurse* OR assistant nurse* OR nurs* OR nursing staff OR emergency paramedic* OR paramedic* OR paramedical personnel OR healthcare assistant* OR healthcare support worker* OR emergency medical technician* OR allied health personnel) AND (2019-nCoV infection OR 2019-nCoV disease OR coronavirus disease-19 OR severe acute respiratory syndrome coronavirus 2 OR SARS-CoV-2 virus OR SARS-CoV-2 infection OR COVID-19 OR SARS-CoV-2) AND (COVID-19 pandemic OR pandemic*) AND (mental health OR angst OR nervousness OR hypervigilance OR anxiousness OR anxiety OR anxiety disorder* OR depressive syndrome OR melancholia OR depressive symptom OR emotional depression OR dysthymia OR depressi* OR depressive disorder* OR dysthymic disorder* OR acute stress disorder* OR life stress OR psychologic stress OR psychological stressor OR stress disorders, traumatic, acute OR stress, psychological OR self-confidence OR self-efficacy)) J. Clin. Med. 2021,10, 5578 6 of 32 Table 1. Cont. Database Search Strategy LILACS (tw:((“emergency medical service*” OR “servicio* medico* de urgencia”) AND (“health personnel” OR “personal de salud” OR physician* OR “medical staff” OR medico* OR “cuerpo medico” OR nurse* OR “nursing staff” OR “enfermera* y enfermero*” OR “personal de enfermería” OR “emergency medical technician*” OR “allied health personnel” OR “técnico* medio* en salud”) AND (“COVID-19” OR “SARS-CoV-2” OR “infeccion* por coronavirus” OR “virus del SARS”) AND pandemic* OR pandemia*) AND (“mental health” OR “salud mental” OR anxiety OR “anxiety disorder*” OR ansiedad OR depression OR “depressive disorder*” OR depresión OR “stress disorder*, traumatic, acute” OR “stress, psychological” OR “trastorno* de estrés traumático agudo” OR “estrés psicológico” OR “self-efficacy” OR autoeficacia) Medline (((emergency medical services[MeSH Terms] OR “prehospital emergency care”[All Fields] OR “emergency care” [All Fields] OR "emergency system"[All Fields] OR "out of hospital"[All Fields] OR “emergency medical service*” [All Fields]) AND (health personnel[MeSH Terms] OR “health care provider”[All Fields] OR “healthcare worker*”[All Fields] OR “health care professional*”[All Fields] OR “health personnel”[All Fields]) OR (physicians[MeSH Terms] OR medical staff[MeSH Terms] OR “physician*, primary care”[All Fields] OR doctor*[All Fields] OR physician*[All Fields] OR “medical staff” [All Fields]) OR (nurse[MeSH Terms] OR nursing staff[MeSH Terms] OR “nursing personnel”[All Fields] OR “registered nurse*”[All Fields] OR "assistant nurse*"[All Fields] OR nurs*[All Fields] OR “nursing staff” [All Fields]) OR (emergency medical technicians[MeSH Terms] OR allied health personnel[MeSH Terms] OR “emergency paramedic*”[All Fields] OR paramedic*[All Fields] OR “paramedical personnel”[All Fields] OR “healthcare assistant*”[All Fields] OR “healthcare support worker*”[All Fields] OR “emergency medical technician*”[All Fields] OR “allied health personnel”[All Fields])) AND ((COVID-19[MeSH Terms] OR SARS-CoV-2[MeSH Terms] OR “2019-nCoV infection”[All Fields] OR “2019-nCoV disease”[All Fields] OR “coronavirus disease-19”[All Fields] OR “severe acute respiratory syndrome coronavirus 2”[All Fields] OR “SARS-CoV-2 virus”[All Fields] OR “SARS-CoV-2 infection”[All Fields] OR “COVID-19”[All Fields] OR “SARS-CoV-2”[All Fields]) AND (pandemics[MeSH Terms] OR “COVID-19 pandemic”[All Fields] OR pandemic*[All Fields])) AND ((mental health[MeSH Terms] OR “mental health”[All Fields]) OR (anxiety[MeSH Terms] OR anxiety disorders[MeSH Terms] OR angst[All Fields] OR nervousness[All Fields] OR hypervigilance[All Fields] OR anxiousness[All Fields] OR anxiety[All Fields] OR “anxiety disorder*”[All Fields]) OR (depression[MeSH Terms] OR depressive disorder[MeSH Terms] OR “depressive syndrome”[All Fields] OR melancholia[All Fields] OR “depressive symptom*”[All Fields] OR “emotional depression”[All Fields] OR dysthymia[All Fields] OR depression[All Fields] OR “depressive disorder*”[All Fields]) OR (stress disorders, traumatic, acute[MeSH Terms] OR stress, psychological[MeSH Terms] OR “acute stress disorder”[All Fields] OR “life stress”[All Fields] OR “psychologic stress”[All Fields] OR “psychological stressor”[All Fields] OR “stress disorders, traumatic, acute”[All Fields] OR “stress, psychological”[All Fields]) OR (self-efficacy[MeSH Terms] OR "self-confidence"[All Fields] OR “self-efficacy”[All Fields]))) PyscoDoc (prehospital emergency care OR emergency care OR emergency system OR out of hospital OR emergency medical service*) AND (health care provider OR healthcare worker* OR health care professional* OR health personnel OR physician*, primary care OR doctor* OR physician* OR medical staff OR nursing personnel OR registered nurse* OR assistant nurse* OR nurs* OR nursing staff OR emergency paramedic* OR paramedic* OR paramedical personnel OR healthcare assistant* OR healthcare support worker* OR emergency medical technician* OR allied health personnel) AND (2019-nCoV infection OR 2019-nCoV disease OR coronavirus disease-19 OR severe acute respiratory syndrome coronavirus 2 OR SARS-CoV-2 virus OR SARS-CoV-2 infection OR COVID-19 OR SARS-CoV-2) AND (COVID-19 pandemic OR pandemic*) AND (mental health OR angst OR nervousness OR hypervigilance OR anxiousness OR anxiety OR anxiety disorder* OR depressive syndrome OR melancholia OR depressive symptom OR emotional depression OR dysthymia OR depressi* OR depressive disorder* OR dysthymic disorder* OR acute stress disorder* OR life stress OR psychologic stress OR psychological stressor OR stress disorders, traumatic, acute OR stress, psychological OR self-confidence OR self-efficacy) J. Clin. Med. 2021,10, 5578 7 of 32 Table 1. Cont. Database Search Strategy PsycINFO (prehospital emergency care OR emergency care OR emergency system OR out of hospital OR emergency medical service*) AND (health care provider OR healthcare worker* OR health care professional* OR health personnel OR physician*, primary care OR doctor* OR physician* OR medical staff OR nursing personnel OR registered nurse* OR assistant nurse* OR nurs* OR nursing staff OR emergency paramedic* OR paramedic* OR paramedical personnel OR healthcare assistant* OR healthcare support worker* OR emergency medical technician* OR allied health personnel) AND (2019-nCoV infection OR 2019-nCoV disease OR coronavirus disease-19 OR severe acute respiratory syndrome coronavirus 2 OR SARS-CoV-2 virus OR SARS-CoV-2 infection OR COVID-19 OR SARS-CoV-2) AND (COVID-19 pandemic OR pandemic*) AND (mental health OR angst OR nervousness OR hypervigilance OR anxiousness OR anxiety OR anxiety disorder* OR depressive syndrome OR melancholia OR depressive symptom OR emotional depression OR dysthymia OR depressi* OR depressive disorder* OR dysthymic disorder* OR acute stress disorder* OR life stress OR psychologic stress OR psychological stressor OR stress disorders, traumatic, acute OR stress, psychological OR self-confidence OR self-efficacy) Scopus (ALL(“prehospital emergency care” OR “emergency care” OR “emergency system” OR “out of hospital” OR “emergency medical service*”)) AND (ALL(“health-care provider” OR “health-care worker*” OR “health care professional*” OR “health personnel” OR “physician*, primary care” OR doctor* OR physician* OR “medical staff” OR “nursing personnel” OR “registered nurse*” OR “assistant nurse*” OR nurs* OR “nursing staff” OR “emergency paramedic*” OR paramedic* OR “paramedical personnel” OR “healthcare assistant*” OR “healthcare support worker*” OR “emergency medical technician*” OR “allied health personnel”)) AND (ALL(“2019-nCoV infection” OR “2019-nCoV disease” OR “coronavirus disease-19” OR “severe acute respiratory syndrome coronavirus 2” OR “SARS-CoV-2 virus” OR “SARS-CoV-2 infection” OR “COVID-19” OR “SARS-CoV-2”)) AND (ALL(“COVID-19 pandemic” OR pandemic*)) AND (ALL(“mental health” OR angst OR nervousness OR hypervigilance OR anxiousness OR anxiety OR “anxiety disorder*” OR “depressive syndrome” OR melancholia OR “depressive symptom” OR “emotional depression” OR dysthymia OR depressi* OR “depressive disorder*” OR “dysthymic disorder*” OR “acute stress disorder*” OR “life stress” OR “psychologic stress” OR “psychological stressor” OR “stress disorders, traumatic, acute” OR “stress, psychological” OR “self-confidence” OR “self-efficacy”)) World of Science (WoS) (TS = (“prehospital emergency care” OR “emergency care” OR “emergency system” OR “out of hospital” OR “emergency medical service*”)) AND (TS = (“health-care provider” OR “healthcare worker*” OR “health-care professional*” OR “health personnel” OR “physician*, primary care” OR doctor* OR physician* OR “medical staff” OR “nursing personnel” OR “registered nurse*” OR “assistant nurse*” OR nurs* OR “nursing staff” OR “emergency paramedic*” OR paramedic* OR “paramedical personnel” OR “healthcare assistant*” OR “healthcare support worker*” OR “emergency medical technician*” OR “allied health personnel”)) AND (TS = (“2019-nCoV infection” OR “2019-nCoV disease” OR “coronavirus disease-19” OR “severe acute respiratory syndrome coronavirus 2” OR “SARS-CoV-2 virus” OR “SARS-CoV-2 infection” OR “COVID-19” OR “SARS-CoV-2”)) AND (TS = (“COVID-19 pandemic" OR pandemic*)) AND (TS = (“mental health” OR angst OR nervousness OR hypervigilance OR anxiousness OR anxiety OR “anxiety disorder*” OR “depressive syndrome” OR melancholia OR “depressive symptom” OR “emotional depression” OR dysthymia OR depressi* OR “depressive disorder*” OR “dysthymic disorder*” OR “acute stress disorder*” OR “life stress” OR “psychologic stress” OR “psychological stressor” OR “stress disorders, traumatic, acute” OR “stress, psychological” OR “self-confidence” OR "self-efficacy”)) The * is used to search for terms with the same root. The selected research studies had to meet the following inclusion criteria: (1) being original, (2) based on qualitative and/or quantitative methods, (3) with any methodological design, (4) submitted for peer-review, (5) published in English, Spanish, French, Italian or Portuguese, (6) completed after December 2019, (7) without geographic limitation, (8) with at least the abstract available, and (9) that in their results evaluated the impact of possible exposure to SARS-CoV-2 on levels of stress, anxiety, depression and/or self-efficacy of the HPs who were working in public, private, or voluntary out-of-hospital EMS during the COVID-19 pandemic or identified factors related positively or negatively with these levels or compared them with those obtained in other working environments and/or professional categories. Opinion articles and editorials, studies of low scientific-technical quality, those that did not reply to the posed research question and/or were not in line with the objective of the review, as well as others that, despite including out-of-hospital HPs, contributed no specific data on this subgroup in their results were excluded. J. Clin. Med. 2021,10, 5578 8 of 32 Critical Appraisal Tools from JBI of the University of Adelaide (Australia) [ 47 ], considered adequate for the design of the study [ 48 , 49 ], were used to evaluate the scientific– technical quality of the selected articles as well as to determine the extent to which the risk of bias was reduced or eliminated in their design, performance, and/or analysis. These multiple-choice questionnaires have four response options (“yes”, “no”, “unclear”, and “not-applicable”) in a way that a greater number of “yes” responses point to a study of better methodological quality. Each individual study was classified as having a low-, moderate-, or high-risk level of bias based on the number of items answered with “yes”. For qualitative studies (10 items), the methodological quality was considered low, moderate, or high if three or less, four to seven, or more than eight criteria were met, respectively [ 48 ]. For cross-sectional studies (8 items), the methodological quality was considered low, moderate, or high if two or less, moderate if three to five, and high if six to eight criteria were met, respectively [ 49 ]. High methodological quality was established for the inclusion of studies in the review. Prior to its use, a trial test was carried out in which the reviewers (N.G.S.B., H.O.B., J.J.J.A., A.M.R.M., M.M.O., J.J.F.D., M.P.M.H., and A.M.S.) had to evaluate three articles, subsequently analyzing the degree of concordance between their evaluations. A standardized data-extraction form was designed in accordance with the JBI [ 50 ] recommendations with the purpose of guaranteeing the homogeneity of researchers in the collection of the information as well as facilitating its subsequent analysis and comparison. Based on the research question formulated as well as the inclusion and exclusion criteria considered, the following data were specifically extracted from each selected article: title and principal author, country and year of publication, objective, type of study, place and period undertaken, size and characteristics of the sample, definition of variables under analysis and instruments used, principal results obtained, conclusions of the study and scientific–technical quality. Eight reviewers (N.G.S.B., H.O.B., J.J.J.A., A.M.R.M., M.M.O., J.J.F.D., M.P.M.H., and A.M.S.) previously piloted this data-extraction form on a random sample of three included studies to ensure the agreement among the interpretation of different data items. One group of reviewers (N.G.S.B., H.O.B., J.J.J.A., and J.F.F.D.) extracted data from the included studies using this form, whereas the second one (A.M.R.M., M.M.O, M.P.M.H., and A.M.S.) verified the extracted data. Three independent reviewers (R.S.C., R.M.C.G., and S.N.P.) screened out possible relevant studies by titles and abstracts, excluding records that did not meet the inclusion criteria. All the works that had initially been identified in each of the databases consulted were included in Mendeley ® Reference Manager (Elsevier, New York, US), with the objective of removing duplicates. The final selection of the studies, the evaluation of their methodological quality, and the data-extraction was completed in pairs (N.G.S.B.–H.O.B., J.J.J.A.–J.J.F.D., A.M.R.M.–M.M.O., and M.P.M.H.–A.M.S.), independently with blind reviews, thereby resolving any possible discrepancies through consensus and, in its absence, calling for the participation of a third evaluator (R.M.C.G.). In the face of any doubt or relevant data unavailable in the selected studies, we planned to contact the corresponding author directly, requesting the necessary clarifications. Because the field of COVID-19 research is moving relatively quickly and new knowledge evidence is continually emerging, an update plan for this systematic review is needed in order to provide convincing evidence for HPs and policymakers. For this, identical search operations will be performed by R.S.C., R.M.C.G., and S.N.P. to identify newly published data. In those databases that have an automatic alert system, these will be configured to provide a feed of new appointments every two weeks. In those others in which automatic alerts are not available, a manual search will be carried out every two weeks. An updated review will be resubmitted when there are relevant changes in the results or when heterogeneity becomes substantial. This systematic review will be maintained in living mode for at least 12 months from publication, although it could be extended at 6-monthly intervals if further evidence is published regularly. J. Clin. Med. 2021,10, 5578 9 of 32 3. Results The initial search returned a result of 2229 identified papers, of which 799 were deleted as duplicates. After reading the title and abstract, 1361 studies were discarded because they were not aligned with the objective of the review or failed to meet the previously established criteria for inclusion. A total of seven new references were found when completing an inverse manual search. With the 99 studies that were considered potentially relevant and met the eligibility criteria, critical readings of their complete texts led to the removal of 22 that were unrelated to the objective of the review, 9 because of their publication format (editorials or opinion-based articles), 46 for contributing no data from out-of-hospital HPs, and 8 for not reaching the minimum required score in the evaluation of their methodological quality. Finally, 20 articles were agreed upon to form part of the review (Figure 3). With regard to the selection process of the studies, from among the 99 articles considered of potential relevance, each evaluator undertook a critical reading of 25, requiring the participation of a third evaluator on 7 occasions. At no time was it necessary to contact the authors of the studies. Figure 3. PRISMA 2020 flow diagram for the study selection process, which included searches of databases, registers, and other sources. Neither a meta-analysis nor a meta-synthesis could be conducted with the studies included in the review due to the high levels of observed heterogeneity between the participants, in the area of development, in the scales and measurement instruments used, and with the final results. Furthermore, areas of uncertainty related to the scarcity of studies carried out with EMS professionals were identified since the COVID-19 pandemic is a recent event, never before experienced, which limits the scientific literature on this phenomenon. The update plan of this systematic review will allow the identification of new studies about stress, anxiety, depression, and self-efficacy in out-of-patients HPs. A meta-analysis or a meta-synthesis will be performed to analyze the evidence of any new eligible studies or data that are obtained. J. Clin. Med. 2021,10, 5578 16 of 32 Table 2. Cont. Study/Author Objetive/Methodology Main Findings Vagni et al. [65] 2020 Objective: To identify the capabilities of HPs to resist COVID-19 pandemic-related stress, associated with the risk of developing symptoms of secondary trauma. Design: Descriptive cross-sectional. Participants: HPs and emergency workers. Setting: Italy. Data collection: Online survey distributed during the pandemic. Main outcomes—Instruments: Acute stress—ESQ; Post-traumatic stress—STSS-I. n= 236 participants (139 females, 97 males; aged 43.24 ±11.06; 56.8% treated COVID-19 patients directly), of whom 140 were included in the Health group (44 females, 95 males; 64 physicians, 55 nurses, 11 operators, 10 psychologists; 72.9% treated COVID-19 patients directly) and 96 in the Emergency group (52 females, 45 males; 51 ambulance workers, 45 other operators such as firefighters, police or Civil Protection staff; 33.3% treated COVID-19 patients directly). No statistically significant differences were observed at the levels of stress or symptoms of secondary trauma in the workers of the Emergency group. In comparison with the HPs from the Healthcare group, those included in the Emergency Group presented lower levels of total stress (84.34 ±15.01 vs. 69.69 ±19.02, d= 1.09, p< 0.01), organizational–relational stress (22.04 ±4.69 vs. 19.32 ±3.61, d= 0.65, p< 0.01), physical stress (10.09 ±5.24 vs. 8.07 ±4.48, d= 0.41, p< 0.05), inefficacy–decisional stress (14.72 ±2.47 vs. 12.77 ±2.47, d= 0.79, p< 0.01), emotional stress (13.90 ±3.58 vs. 10.58 ±3.49, d= 0.90, p< 0.01), cognitive stress (8.65 ±2.89 vs. 6.10 ±2.34, d= 0.94, p< 0.01), COVID-19 stress (15.18 ±3.49 vs. 12.85 ±4.09, d= 0.61, p< 0.01), as well as the degree of physiological and psychological activation (26.48 ±4.04 vs. 23.69 ±4.27, d= 0.67, p< 0.01). The women from the Emergency group reported major physical stress (9.41 ±4.70 vs. 6.94 ±3.99, p< 0.01) and emotional stress (11.52 ±3.94 vs. 9.79 ±2.86, p< 0.05); whereas the men obtained greater inefficacy–decisional stress (13.37 ±2.34 vs. 12.07 ±2.46, p< 0.05). No significant differences were observed for stress levels among HPs as a function of direct assistance to patients with COVID-19 or otherwise. Not belonging to the Emergency group was a risk factor of an increased degree of physiological and psychological activation as well as a symptom of secondary trauma (β=−0.338, p< 0.001). J. Clin. Med. 2021,10, 5578 17 of 32 Table 2. Cont. Study/Author Objetive/Methodology Main Findings Vagni et al. [66] 2020 Objective: To identify the mediating effect of resistance and the coping strategies activated by emergency services workers to withstand the stress and symptoms of secondary trauma caused by the COVID-19 pandemic. Design: Descriptive cross-sectional. Participants: Red Cross Emergency volunteers. Setting: Venice (Italy). Data collection—Instrument: Online survey distributed during forced home confinement. Main outcomes—Instruments: Acute stress—ESQ; Post-traumatic stress—STSS-I; Self-efficacy—CSES-SF. n= 513 volunteers (286 females, aged 44.49 ±12.99 years; 227 males, aged 47.10 ±13.51 years; weekly work 13.49 ±11.62 h). All subscales of stress showed a positive correlation with secondary trauma and a negative one with coping strategies. The women presented significantly higher scores for physical stress (6.88 ± 4.83 vs. 4.86 ± 4.53, p< 0.001), emotional stress (8.33 ± 4.18 vs. 7.41 ± 4.69, p< 0.05), degree of physiological and psychological activation (11.86 ±3.99 vs. 9.84 ±4.17, p< 0.001), avoidance behavior (12.70 ±3.56 vs. 11.47 ±3.89, p< 0.001) and obsessive thoughts (9.69 ± 3.14 vs. 8.86 ± 3.28, p< 0.01), whereas the men scored significantly higher in problem-focused coping strategies (39.00 ±6.42 vs. 37.82 ± 6.49, p< 0.05). Weekly hours of work had no effect on the stress factors, the symptoms of secondary trauma, and the coping strategies. Being a woman was a predictive factor of physical stress (β= 0.383, p< 0.001), degree of physiological and psychological activation (β= 0.890, p< 0.001), avoidance behavior (β= 0.508, p< 0.05), and obsessive thoughts (β= 0.464, p< 0.05). Age was a predictive factor of physical stress (β=−0.117, p< 0.01), organizational–relational stress ( β = − 0.105, p< 0.05), emotional stress ( β = − 0.102, p< 0.05), cognitive stress (β=−0.091, p< 0.05), avoidance behavior (β= 0.032, p< 0.01), and obsessive thoughts (β= 0.049, p< 0.001). Having no personal protection equipment was a predictive factor of organizational–relational stress ( β = 0.304, p< 0.001), physical stress (β= 0.116, p< 0.01), emotional stress (β= 0.129, p< 0.01), cognitive stress (β= 0.233, p< 0.001), and avoidance behavior (β= 0.081, p< 0.05). Stopping unpleasant emotions and thoughts coping strategy was a predictive factor of organizational–relational stress (β=−0.156, p< 0.01), physical stress (β=−0.332, p< 0.001), emotional stress (β=−0.353, p< 0.001), cognitive stress (β=−0.244, p< 0.001), COVID-19 stress (β=−0.252, p< 0.001), degree of physiological and psychological activation (β= 0.039, p< 0.05), and obsessive thoughts (β= 0.032, p< 0.05). Supportting a coping strategy was a predictive factor of avoidance behavior (β= 0.057, p< 0.05). Organizational–relational stress was a predictive factor of obsessive thoughts (β=−0.079, p< 0.05), physical stress, degree of physiological and psychological activation (β= 0.334, p< 0.001); avoidance behavior (β= 0.147, p< 0.001) and obsessive thoughts (β= 0.122, p< 0.001); inefficacy–decisional stress, of obsessive thoughts (β= 0.064, p< 0.05); emotional stress, of the degree of physiological and psychological activation (β= 0.270, p< 0.001), avoidance behavior (β= 0.222, p< 0.001), and obsessive thoughts (β= 0.189, p< 0.001); cognitive stress, of avoidance behavior (β= 0.237, p< 0.001) and obsessive throughts (β= 0.129, p< 0.05); and COVID-19 stress, degree of physiological and psychological activation (β= 0.127, p< 0.001), avoidance behavior (β= 0.078, p< 0.05), and obsessive thoughts ( β = 0.254, p< 0.001). Total stress had predictive effects on the degree of physiological and psychological activation (β= 0.698, p< 0.001) and avoidance behavior (β=−0.391, p< 0.001); in both cases, problem-focused and “stop unpleasant emotional thoughts” coping strategies acted as mediating factors. J. Clin. Med. 2021,10, 5578 18 of 32 Table 2. Cont. Study/Author Objetive/Methodology Main Findings Vagni et al. [67] 2021 Objective: To examine the relationships between emergency stress and coping strategies in HPs and compare the results of the first and second waves. Design: Descriptive cross-sectional. Participants: HPs and emergency workers active in different sectors during the COVID-19 pandemic. Setting: Italy. Data collection—Instrument: Online survey distributed during the forced home confinement on April 2020 and during the second pandemic wave between November and December 2020. Main outcomes—Instruments: Acute stress—ESQ, PSS; Post-traumatic stress—STSS-I; Burnout—MBI; Self-efficacy—CSES-SF. n= 500 participants. In the first wave, 140 were included in the Health group (74 physicians, 66 nurses) and 100 in the Emergency group (100 emergency workers); in the second wave, 179 HPs were included in the Health group (50 physicians, 129 nurses) and 81 in the Emergency group (81 emergency workers); 63.7% and 72.3% worked with COVID-19 patients on the first and second waves, respectively. The total stress levels of the Emergency group did not differ between the two waves of the pandemic; physical stress was greater in the second wave. No differences were observed in the coping strategies used by the participants. An analysis of burnout levels in the second wave found that total stress levels showed a high predictive power in the emotional exhaustion (β= 0.62; p< 0.001) and depersonalization (β= 0.20; p< 0.001) subscales. Vanhaecht et al. [68] 2021 Objective: To determine the effect of COVID-19 on the positive or negative symptoms of mental health of HPs, identifying sources of support from the workplace authorities. Design: Descriptive cross-sectional. Participants: HPs working during the week before the completion of the questionnaire. Setting: Flanders (Belgium). Data collection: Online survey distributed through social networks between 2 April and 4 May 2020. Main outcomes—Instruments: Mental health symptoms—frequency of 19 negative and positive signs and symptoms of mental health (ad hoc). n= 4503 HPs, of whom 1831 were paramedics. A greater occurrence of negative symptoms was observed among the paramedics during the COVID-19 pandemic in relation to the previous situation: stress (OR 5.42, 95%CI 4.79–6.13), hypervigilance (OR 10.95, 95%CI 9.59–12.51), fatigue (OR 5.15, 95%CI 4.56–5.83), difficulty sleeping (OR 6.04, 95%CI 5.33–6.84), unable to relax (OR 4.24, 95%CI 3.75–4.80), fear (OR 9.88, 95%CI 8.66–11.27), irregular lifestyle (OR 4.06, 95%CI 3.56–4.05), difficulty concentrating (OR 4.33, 95%CI 3.81–4.92), unhappy and dejected (OR 4.96, 95%CI 4.35–5.65), failure to recognize own emotional response (OR 3.88, 95%CI 3.40–4.44), doubting knowledge and skills (OR 2.90, 95%CI 2.57–3.28), feeling on their own (OR 3.16, 95%CI 2.78–3.58), avoiding risks (OR 4.31, 95%CI 3.77–4.91), leaving the profession (OR 2.47, 95%CI 2.15–2.85), and uncomfortable within a team (OR 2.59, 95%CI 2.28–2.95). Positive symptoms such as forming part of a team (OR 0.69, 95%CI 0.61–0.78), making a difference (OR 0.80, 95%CI 0.71–0.91), and sufficient support guidance (OR 0.74, 95%CI 0.66–0.84) were less likely to be present within this group during the COVID-19 pandemic in relation to the previous situation. Likewise, a significant modification of the effect was observed according to professional category since the ORs for all symptoms were lower in paramedics relative to nurses. Vujanovic et al. [69] 2021 Objective: To evaluate the impact of exposure to COVID-19 on the mental health of first-line healthcare workers. Design: Descriptive cross-sectional. Participants: First-line healthcare workers older than 18 years in age. Setting: United States. Data collection: Online survey distributed by email between June and August 2020. Main outcomes—Instruments: Anxiety—OASIS; Depression—ODSIS; Post-traumatic stress—PCL-5 adapted to COVID-19; Mental health—MHCQ. n= 189 first aid responders (40 females, 149 males; aged 47.6 ± 10.9 years; 60 firefighter, 35 EMS, 91 firefighters—EMS, 3 firefighters—EMS law enforcement). In all, 6.8% fitted the clinical criteria for post-traumatic stress, 18.4% for anxiety, and 16.8% for depression. Among the first-aid responders, those who reported exposure to COVID-19 (n= 122) had a high consumption of alcohol (p= 0.016), worked in an EMS (p= 0.03), or had obtained a recognized qualification (p= 0.04). Their mean level of anxiety was 4.57 ±0.36 and their mean level of depression was 3.83 ±0.38, observing no statistically significant differences in both variables as a function of exposure to COVID-19 or otherwise (p> 0.05). A greater concern for COVID-19 was related with higher levels of anxiety (β= 0.52, p< 0.001), depression (β= 0.34; p< 0.001), or presence of post-traumatic stress symptoms (β= 0.71, p< 0.001). A greater medical vulnerability was related to higher levels of anxiety (β= 0.16, p< 0.012) or depression (β= 0.25, p< 0.012). A shorter working life was related to higher levels of depression (β=−0.18, p< 0.013). J. Clin. Med. 2021,10, 5578 19 of 32 Table 2. Cont. Study/Author Objetive/Methodology Main Findings Zolnikov et al. [70] 2020 Objective: To understand the stigma and consequences for the mental health of first-aid responders during the COVID-19 pandemic. Design: Qualitative with a phenomenological focus. Participants: HPs and first-aid responders, older than 18 years, who had worked during the COVID-19 pandemic. Setting: Canada, United States, Ireland, Kenya. Procedure—Data collection: Semi-structured interviews conducted over the telephone. Convenience sampling was used to select participants through different social networks. n= 31 participants (18 females, 13 males; aged 36.13 years; 3 physicians, 14 nurses, 1 nurse tech, 1 behavioral therapist, 1 orthodontist, 1 dialysis technician, 1 technician in medical surgery, 1 data specialist, 1 paramedic, 3 firefighters and paramedics, 1 firefighter and medical emergency technician, 3 police officers). The first-aid responders expressed feelings of isolation and the lack of support and understanding among family and friends, reduction or forced removal in immediate social interactions, feelings of being infected or dirty, increased feelings of sadness and anxiety, and refusal to seek help or to receive treatment. HP: healthcare professional; COVID-19: coronavirus disease; EMS: Emergency Medical Services; GAD-2: Generalized Anxiety Disorder 2-items; PHQ-2: Patient Health Questionnaire 2; OR: odds ratio; STAI: State-Trait Anxiety Inventory; ESQ: Emergency Stress Questionnaire; STSS-I: Secondary Traumatic Stress Scale—Italian version; CSES-EF: Coping Self-Efficacy Scale—Short Form; DTS-8: Davidson Trauma Scale; GHQ-12: General Health Questionnaire; GAD-7: Generalized Anxiety Disorder 7; PR: prevalence ratio; CI: confidence interval; PSM-25: Psychological Stress Measure; MBI: Maslach Burnout Inventory; PSS: Perceived Stress Scale; OASIS: Overall Anxiety Severity and Impairment Scale; ODSIS: Overall Depression Severity and Impairment Scale: PCI-5: Post-traumatic Stress Disorder Checklist for DSM-5, adapted to COVID-19; MHCQ: Mental Health Correlates Questionnaire. 3.1. Description of the Characteristics of the Studies The designs of most of the selected research (n= 16) were of the descriptive crosssectional type [ 52 , 54 – 57 , 59 – 69 ], except in the case of the 4 remaining studies in which a qualitative methodology was used [ 51 , 53 , 58 , 70 ]. With regard to their geographic distribution, the studies were completed in regions and countries with important differences in the organization of their health systems: Italy (n= 6) [ 56 , 63 – 67 ], Germany (n= 2) [ 52 , 59 ], Spain (n= 2) [ 57 , 61 ], Turkey (n= 2) [ 55 , 62 ], Belgium (n= 1) [ 68 ], India (n= 1) [ 53 ], Iran (n= 1) [ 51 ], Pakistan (n= 1) [ 58 ], Poland (n= 1) [ 54 ], Russia (n= 1) [ 60 ], and the United States (n= 1) [ 69 ]. It is worth mentioning that professionals from four different countries (Canada, Ireland, Kenya and the United States) participated in one of the qualitative studies [70]. The levels of stress, anxiety, depression, and self-efficacy of the out-of-hospital HPs during the COVID-19 pandemic were some of the results analyzed in the selected studies. Other results such as fear, sleep quality, resilience level, and substance abuse were not objects of evaluation in the present review, despite having been recurrent topics in the works under analysis. In most studies, the area of work was considered yet another secondary variable, including all the HPs regardless of the area in which they might work [ 54 – 56 , 59 – 61 , 63 – 68 ]. No great differences were found in the inclusion and exclusion criteria under consideration. In the majority of works, the participants had to be practicing HPs who, during the COVID-19 pandemic, were working in a health institution and/or organization. A high degree of variability was observed with regard to the number and professional category of the out-of-hospital health workers in the included and analyzed studies. The sample size ranged from 31 to 1831 participants in the descriptive, crosssectional studies [ 55 , 68 ], while in the qualitative-based studies, this interval was between 3 and 31 participants [ 53 , 70 ]. Paramedics and emergency ambulance technicians were the two professional categories with the highest number of representatives in 11 of the 20 selected articles. Participants ´ profession was not specified in some of the studies under review, in which they were given generic headings such as EMS, ambulance, and emergency workers [ 56 , 61 , 63 – 65 , 67 , 69 ]. Some authors considered collectives that could act as first-aid responders, such as firefighters, police, Civil Protection staff, and Red Cross volunteers, and as out-of-hospital emergency personnel, although they were not HPs [56,63,65,66,69]. In the descriptive, cross-sectional studies, the participants were selected through non-probabilistic convenience sampling based on voluntary participation. In all of them, except in one, data collection was done through the completion of an online survey distributed through the principal social networks (Facebook ® , Instagram ® , LinkedIn ® , Twitter ® , WhatsApp ® ), email lists, and specialized fora and web pages of public orga- J. Clin. Med. 2021,10, 5578 20 of 32 nizations and thematic communities [ 52 , 54 – 57 , 59 – 61 , 63 – 69 ]. Among all the quantitative investigations, the study of Usul et al. was the only one that decided to conduct personal interviews with each of the participants as a data-collection method [ 62 ]. The necessary time to complete the survey fluctuated between 5 and 20 min. The period analyzed in most studies included in this review was the first phase of the COVID-19 pandemic, between the months of March and July 2020, which coincided with an important increase in the global case rate as well as with the adoption of restrictive governmental measures in the great majority of countries, which considerably constrained the individual liberties of the general public [ 52 , 54 – 57 , 59 – 61 , 66 , 69 ]. The study by Vagni et al. was the only one in which data was collected on both waves of the pandemic [ 67 ]. Different questionnaires and scales, of which most were validated, were used to evaluate the possible impact of exposure to SARS-CoV-2 on the mental health of out-of-hospital HPs. Stress levels were assessed through the Emergency Stress Questionnaire (ESQ) [ 56 , 63 – 67 ], the Perceived Stress Scale (PSS) [ 67 ], the Psychological Stress Measure (PSM-25) [ 60 ], and ad hoc questionnaires on stressful factors [ 52 , 54 , 56 , 63 , 64 ]. The Secondary Traumatic Stress Scale—Italian version (STSS-I) [ 56 , 63 , 65 – 67 ], the Davidson Trauma Scale (DTS-8) [ 57 ], and the Post-traumatic Stress Disorder Checklist for DSM-5 adapted to COVID-19 (PCL-5) [ 69 ] were the questionnaires used to evaluate the presence of post-traumatic stress. The development of burnout was valued through the use of the Maslach Burnout Inventory [ 61 , 64 , 67 ]. The State-Trait Anxiety Inventory (STAI) [ 55 , 62 ], the Generalized Anxiety Disorder 7-items (GAD-7) [ 59 ], the Generalized Anxiety Disorder 2-items (GAD-2) [ 52 ], and the Overall Anxiety Severity and Impairment Scale (OASIS) [ 69 ] were chosen to quantify the level of anxiety. The presence of depressive symptoms was evaluated through the Patient Health Questionnaire 2 (PHQ-2) [ 52 , 59 ] and the Overall Depression Severity and Impairment Scale (ODSIS) [ 69 ]. The Coping Self-Efficacy Scale—Short Form (CSES-SF) was the tool chosen to value selfefficacy [ 56 , 63 – 67 ]. Other questionnaires or ad hoc lists were used, such as Attitude of Healthcare Workers towards COVID-19 Pandemic [ 61 ], General Health Questionnaire-12 (CHQ-12) [ 57 ], Frequency of Negative and Positive Mental Health Symptoms [ 68 ], and the Mental Health Correlates Questionnaire (MHCQ) [ 69 ], in which the state of mental health of HPs was evaluated through the presence of certain symptoms. Taking into account the characteristics and instructions of each one of these instruments, the collected data could refer to the time at which the questionnaires were completed, the week immediately before, or other points in time. With regard to the statistical analysis, in most studies, univariate tests were employed to analyze the effect of the different variables on the principal result of the study. In some of them, it was also complemented with multivariate tests for the simultaneous analysis of various variables and the identification of possible predictive factors [52,54,56,61,63–69]. An intentional non-probabilistic sampling was used in the investigations that followed a qualitative methodology, with the purpose of achieving the greatest possible variability in the selection of the participants. Munawar et al. and Zolkinov et al. opted to use social networks during the participant recruitment process [ 58 , 70 ]. The time period for data collection was between March and July 2020 [ 51 , 58 ]. A semi-structured in-depth interview was used as a data-collection instrument, conducted by researchers with expertise in this type of study via telephone [ 51 ], video calls [ 51 , 70 ], or in person [ 53 , 58 ]. George et al. complemented this interview with the creation of four focal discussion groups in which there were 8-to-11 participants [ 53 ]. Thematic analysis was used for data interpretation in two studies [ 51 , 58 ]; in another, ethnographic analysis with an interpretative focus was used [53], and, in yet another, phenomenological descriptive analysis [70]. 3.2. Description of the Results of the Critical Evaluation of the Studies The results of the critical appraisal of the 16 selected studies are summarized in Tables 3and 4. The majority of the studies scored moderately due to the unclear description of certain details of the methodology used. In the descriptive, cross-sectional studies, these details referred to the form of evaluating the mental health of HPs as well as to the way of J. Clin. Med. 2021,10, 5578 21 of 32 identifying and controlling possibly confounding factors; in the qualitative studies, these details referred to the possible influence of the researcher in the study and compliance with the minimum necessary ethical requirements. Only one qualitative study adequately described all the details required according to the critical appraisal applied [70]. Table 3. Critical appraisal of cross-sectional studies. Citation Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Dreher et al. [52] Y Y Y N Y Y N Y Ilczak et al. [54] Y Y Y N Y Y Y Y Karasu et al. [55] Y Y Y Y N N Y Y Maiorano et al. [56] Y Y Y N Y Y N Y Martinez-Caballero et al. [57] Y Y Y Y N N Y Y Skoda et al. [59] Y Y Y Y N N Y Y Sorokin et al. [60] Y Y Y Y N N Y Y Torrente et al. [61] Y Y N N Y Y Y Y Usul et al. [62] Y Y Y Y N N Y Y Vagni et al. [63] Y Y Y N Y Y Y Y Vagni et al. [64] Y Y Y N Y Y Y Y Vagni et al. [65] Y Y Y N Y Y Y U Vagni et al. [66] Y Y N N Y Y Y Y Vagni et al. [67] Y Y Y N Y Y Y Y Vanhaedad et al. [68] Y Y N N Y Y Y Y Vujanovic et al. [69] Y Y N N Y Y Y Y % Y 100.00 100.00 75.00 45.00 75.00 75.00 90.00 90.00 Y: yes; N: no; U: unclear. Q1: Were the criteria for inclusion in the sample clearly defined? Q2: Were the study subjects and the setting described in detail? Q3: Was the exposure measured in a valid and reliable way? Q4: Were objective, standard criteria used for measurement of the condition? Q5: Were confounding factors identified? Q6: Were strategies to deal with confounding factors stated? Q7: Were the outcomes measured in a valid and reliable way? Q8: Was appropriate statistical analysis used? Table 4. Critical appraisal of qualitative studies. Citation Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Arbedilli et al. [51] Y Y Y Y Y Y N N Y Y George et al. [53] U Y Y Y Y Y Y Y U Y Munawar et al. [58] Y Y Y Y Y Y U Y U Y Zolkinov et al. [70] Y Y Y Y Y Y Y Y Y Y % Y 75.00 100.00 100.00 100.00 100.00 100.00 50.00 75.00 50.00 75.00 Y: yes; N: no; U: unclear. Q1: Is there congruity between the stated philosophical perspective and the research methodology? Q2: Is there congruity between the research methodology and the research question or objectives? Q3: Is there congruity between the research methodology and the methods used to collect data? Q4: Is there congruity between the research methodology and the representation and analysis of data? Q5: Is there congruity between the research methodology and the interpretation of results? Q6: Is there a statement locating the researcher culturally or theoretically? Q7: Is the influence of the researcher on the research, and vice-versa, addressed? Q8: Are participants and their voices adequately represented? Q9: Is the research ethical according to current criteria or for recent studies, and is there evidence of ethical approval by an appropriate body? Q10: Do the conclusions drawn in the research report flow from the analysis or interpretation of the data? 3.3. Description of the Results of the Studies 3.3.1. Stress In the selected studies, the level of stress of the HPs was assessed from different perspectives: acute stress, post-traumatic stress, and burnout. Acute Stress From among the 20 selected articles, 14 specifically evaluated stress levels [ 51 – 54 , 56 , 58 , 60 , 63 – 67 ]. The 4698 out-of-hospital participants included EMS workers, ambulance workers, paramedical personnel, firefighters, police, Civil Protection staff, and Red Cross volunteers. The total stress levels did not differ between the two waves of the pandemic [ 67 ]. In relation to the previous situation, a greater J. Clin. Med. 2021,10, 5578 22 of 32 frequency of stress was observed among the paramedics during the COVID-19 pandemic [ 68 ]. In comparison with other HPs, the out-of-hospital workers obtained lower levels of total stress, organizational–relational stress, physical stress, inefficacy– decisional stress, emotional stress, cognitive stress, and COVID-19 stress. Women experienced physical and emotional stress with greater frequency [ 65 , 66 ], while the men scored significantly higher for inefficacy–decisional stress [ 65 ]. Older-aged workers obtained higher levels of organizational–relational stress, physical stress, emotional stress, and cognitive stress [ 64 – 66 ]. Nurses experienced higher levels of stress at work than paramedics during the pandemic [ 54 ]. The hours of weekly work had no effect on the subscales of stress [ 54 , 66 ]. Having direct contact with patients affected by COVID-19 or the fear of contracting the disease favored the appearance of total stress and inefficacy–decisional stress [ 54 , 56 , 64 ], not observing any effect of this variable in a study completed by Vagni et al. [ 65 ]. Non-availability of adequate personal protective equipment and a decrease in the level of safety and security while conducting emergency medical procedures were the risk factors for the development of organizational relational stress, physical stress, emotional stress, cognitive stress, and total stress [ 54 , 66 ]. Another predictor of occupational stress was the marginalization of patients not suffering from COVID-19 [ 54 ]. When asking the participants in one of the qualitative studies on possible stress-related factors, the following emerged: uncertainty over the pandemic, fear of death, the feeling of guilt for having passed the illness to their loved ones, anxiety over the likelihood of violence from patients, and exhaustion [53]. Post-Traumatic Stress With regard to post-traumatic stress, this aspect is specifically analyzed in seven articles [ 56 , 57 , 63 , 65 , 66 , 69 ]. The 1485 out-of-hospital HPs who participated in the studies were distributed among EMS workers, ambulance workers, firefighters, firefighters-EMS law enforcement, police, Civil Protection staff, and Red Cross volunteers. 6.8% of participants presented symptoms consistent with post-traumatic stress [ 69 ]. The degree of physiological and psychological activation was altered with greater frequency among both women and out-of-hospital HPs [56,65,66,69]. Being a woman and being an older person were related to higher levels of avoidance behavior and obsessive thoughts [ 66 ]. The weekly hours of work had no effect on the symptoms of secondary trauma [ 66 ]. The risk of probability of developing symptoms of post-traumatic stress was related to gender, changes in job functions, having had prior theoretical and practical training of the use of personal protective equipment, having been worried about contracting the disease, anxiety symptoms prior to and during the pandemic, use of anxiolytics during the pandemic, requiring psychological support prior and during the pandemic, and dealing with mental health issues normally in the work unit [ 57 ]. The non-availability of adequate personal protective equipment was a risk factor for the development of post-traumatic stress and avoidance behavior [ 57 , 66 ]. Greater concern over COVID-19 was related to a higher probability of developing symptoms of post-traumatic stress [69]. Burnout The level of burnout was evaluated in 3 of the 20 selected studies [ 61 , 64 , 67 ], in which the sample was formed of 309 EMS workers and 157 volunteers. In all the subscales of stress, a positive correlation was observed with emotional exhaustion and depersonalization and a negative correlation was observed with personal accomplishment [ 64 ]. In the second wave of the pandemic, total stress levels showed a high predictive power in emotional exhaustion and depersonalization [ 67 ]. Torrente et al. observed no differences in levels of burnout among HPs as a function of professional category and field of work [ 61 ]. In turn, Vagni et al. demonstrated that personal accomplishment was reduced among out-of-hospital workers of older age, increasing among those entering into direct contact with COVID-19 patients [64]. J. Clin. Med. 2021,10, 5578 23 of 32 3.3.2. Anxiety Anxiety levels were evaluated in 8 of the 20 studies [ 51 , 52 , 55 , 58 , 59 , 62 , 69 , 70 ]; 2133 individuals participated, of whom 20 were physicians, 14 were nurses, 1590 were paramedics, 251 were emergency medical technicians, 53 were drivers, 43 were EMS- workers, 63 were firefighters, 93 were firefighters—EMS, 3 were firefighters—EMS law enforcement, and 3 were police. Around 15–20% of the participants met the established clinical criteria for anxiety [ 54 , 69 ]. The levels of anxiety reported by women were greater than those of men, observing a reduction as the age of the participants increased [ 62 ]. With regard to professional category and scope of work, the results from the different studies were not conclusive: Karasu et al. observed no differences in anxiety levels [ 55 ]; Skoda et al. affirmed that paramedics obtained the lowest levels of anxiety [ 59 ], while for Usul et al. lowest levels of anxiety were experienced by nurses [ 62 ]. Having personal antecedents of any medical condition that increased the risk of suffering COVID-19, being concerned over infecting family and/or friends, thinking they had no proper personal protective equipment, or feeling more nervous were factors that significantly increased the anxiety levels of out-of-hospital HPs [ 62 , 69 ]. HPs with symptoms of anxiety were more frequently reported to be burdened by an increase in workload due to the pandemic, thoughts about SARS-CoV-2 contraction at the workplace, a shortfall of colleagues, the childcare situation, not being able to let patients down, uncertainty about how to act correctly, uncertainty about contact persons, uncertainty about their financial situation, and uncertainty about temporal scope [ 52 ]. Other factors identified in the qualitative studies were the high workloads, the feeling of having lost control of the situation, the feeling of not being useful, isolation and separation from loved ones, lack of support and understanding among family members and friends, and the fear of dying [ 51 , 70 ]. Treating patients with COVID-19 or suspected cases of COVID-19 was a factor that induced anxiety in the study carried out by Usul et al. [ 62 ], observing no influence at all in the one by Vujanovic et al. [ 69 ]. Moreover, thinking that sufficient and adequate information on COVID-19 was available was the only factor that was related to a reduction in anxiety levels [59]. 3.3.3. Depression The presence of depressive symptoms was evaluated in 3 of the 20 selected articles [ 52 , 59 , 69 ]. The sample of out-of-hospital health workers comprised 333 women, 1610 men and 2 diverse individuals, distributed among 1499 paramedics, 35 EMS workers, 60 firefighters, 91 firefighters—EMS, and 3 firefighters—EMS law enforcement. Around 15% of the participants met with the clinical criteria established for a medical history of depression [ 69 ]. No statistically significant differences were observed in the levels of depression of the participants as a function of their professional category [ 59 ]. The out-of-hospital HPs at greater risk of presenting depressive-type symptoms were those who expressed concern over the COVID-19 pandemic, those suffering any illness that increased the risk of being infected with COVID-19, those who did not feel protected by personal protective equipment, and those with less work experience [ 52 , 69 ]. Direct assistance to patients showing signs of COVID-19 or with confirmed cases was unrelated to the frequency of depressive symptoms [ 69 ]. The stressors that increased the likelihood of suffering depressive symptoms were: a shortfall of colleagues, not being able to let patients down, uncertainty about how to act correctly, uncertainty about contact persons, uncertainty about their financial situation, and uncertainty about temporal scope [52]. 3.3.4. Self-Efficacy The self-efficacy of out-of-hospital professionals was evaluated in 6 of the 20 selected articles [ 53 , 56 , 58 , 63 , 66 , 67 ]. The sample was formed of 892 participants, in which the professional categories of EMS workers, firefighters, Civil Protection staff, and voluntary Red Cross personnel were analyzed. Out-of-hospital workers used multiple adaptative interventions and coping strategies in order to promote perceptions of self-efficacy. Some were centered on the thoughts and emotions of the person, with the aim of favoring J. Clin. Med. 2021,10, 5578 24 of 32 cognitive reappraisal and positive reframing; others were focused on the problem in order to reduce the risk of infection, and yet others on the meaning of the situation, so that the stressful experience could help to maintain personal wellbeing in difficult times [ 53 ]. Among them, “stop unpleasant emotions and thoughts” was the strategy used with greater frequency by the out-of-hospital workers [ 53 , 63 ], acting as a predictive factor of less organizational–relational stress, physical stress, emotional stress, cognitive stress, and COVID-19 stress as well as a lesser degree of physiological and psychological activation and obsessive thoughts as symptoms of secondary trauma [ 66 ]. In turn, the men resorted to problem-focused strategies to confront the different situations that might present themselves during the COVID-19 pandemic [ 66 ]. Use of the coping strategy of support was predictive of fewer instances of avoidance behavior as a symptom of secondary trauma [ 66 ]. No differences were observed in the coping strategies used by the participants between the two waves of the pandemic [ 67 ]. In the qualitative study developed by Munawar et al., the 15 emergency ambulance technicians/drivers who were interviewed affirmed that they turned with greater frequency to the following coping strategies to face the situation of uncertainty derived from the COVID-19 pandemic: religion, passion for serving their community and country, the feeling of having complied with their commitment, altruism, empathy, non-exposure to the communications media, and thinking that it is just another emergency [58]. 4. Discussion In this living systematic review, the impact of the COVID-19 pandemic on the mental health of out-of-hospital HPs has been evaluated. Their results have revealed the existence of different factors that have been associated with a greater or lesser risk of developing symptoms of stress, anxiety, and depression as well as the identification of various coping strategies used by HPs to adapt to the situations arising from the COVID-19 pandemic. Being a woman was associated with higher levels of perceived anxiety and stress, similar results to those obtained by health workers from other areas [ 16 , 71 – 76 ]. Likewise, the women recognized that they had had a high degree of physiological and emotional activation, avoidance behaviors, and obsessive thoughts, with greater frequency than men, which are factors that are related to greater susceptibility to the development of post-traumatic stress [ 76 , 77 ]. These results may be due to a series of elements that favor an effect on their mental wellbeing, such as the high feminization of the health sector, discrimination by gender, the difficulty of conciliating family life with work life, the consequences associated with pregnancy and maternity, the lack of support systems, the greater empathetic capacity of women in providing care and helping others, and their greater ability to express their feelings and to develop emotional responses in the face of stressful events [ 76 , 78 – 80 ]. These factors considerably reduce the time that may be dedicated to self-care and self-compassion, which favors the maintenance of this situation over time [ 80 , 81 ]. In addition, the women tended to employ emotion-focused coping strategies, which are less effective under stressful or emergency situations [ 82 , 83 ]. Problemfocused strategies were mainly used by men, limiting their capacity to recognize their emotional difficulties and to create awareness of their own experiences. This strategy is related to a higher risk of presenting psychosomatic complications as a consequence of perceived stress [83]. Age had no uniform influence on the mental health of out-of-hospital workers, in agreement with the results obtained from other studies [ 84 – 90 ]. On the one hand, the older-aged professionals were more vulnerable to the development of symptoms of stress during the COVID-19 pandemic due to the high pressure they were under while at work, their feelings of responsibility towards their colleagues and society, and a greater awareness of the risks and seriousness of the situation [ 84 ]. The feeling of having lost control of the situation and the fear of infection were lived as a continual threat against their own health and that of their family members, especially in the first phases, due to the lack of existing information and knowledge [ 84 , 85 ]. In addition, J. Clin. Med. 2021,10, 5578 25 of 32 an older age was also associated with the adoption of avoidance strategies towards negative thoughts and emotions, which means that the person may be less influenced by intrusive components of their previous traumatic experiences [ 86 ]. On the other hand, their levels of anxiety progressively diminished as their age increased, converting it into a protective factor, which could be related to a higher level of competence and experience at work, a greater feeling of self-esteem, and the activation of internal resources and personal skills for handling adverse situations [ 89 – 91 ]. This protective effect of age was also observed in the development of symptoms of secondary trauma, especially in the studies that were performed after the initial phase of the pandemic [ 66 ]. Having a personal history of any pathology that increased susceptibility to COVID-19 infection was related to higher levels of anxiety and depression, which may be due to a greater concern about infection and its consequences as it implies a higher risk in this group of people. In other areas, similar results have been observed for the presence of depressive symptoms [ 92 ] but not for the anxious type [ 93 , 94 ]. Among HPs from other areas, having a personal history of any mental health disorder, especially those related to substance abuse or depression, was strongly associated with the presentation of a current mental disorder. The higher the number of prior lifetime mental disorders reported, the more likely the prevalence of any current disorder [95]. With regard to professional category and field of work, the results from the studies under analysis were neither unanimous nor conclusive, which can be related to the heterogeneity in the organizations and functional operations of the health systems and out-of-hospital EMS within the different countries. Contrary to what might be expected and to what has been reported in other studies [ 24 , 96 ], Usul et al. were the only authors who identified out-of-hospital nursing professionals as presenting lower levels of anxiety [ 62 ]. In various studies, the impact of the COVID-19 pandemic on the mental health of out-of- hospital health workers and volunteers has been analyzed, comparing their results with those obtained by HPs from other areas. In all of them, levels of anxiety and stress were high, which exposed them to a greater risk of developing symptoms of secondary trauma; however, these levels were lower than those of out-of-hospital workers, especially among paramedics. These challenges can be related to the fact that the front-line workers perceived their actions as the continuity of their habitual procedures and activities, although with higher levels of self-protection and safety, as they were more accustomed to potentially worrying experiences and showed fewer negative responses in the face of challenging situations [ 44 , 97 , 98 ]. In the case of the volunteers, personal motivation, freedom to choose weekly hours of service dedicated to voluntary work, and feelings of gratification when offering their support to others might be the cause of their low stress levels, although they have a greater risk of suffering emotional exhaustion, as happens with the caring professions [16,99,100]. No significant differences have been observed in the impact of the COVID-19 pandemic on the mental health of out-of-hospital HPs in different regions. However, this situation has shown the existence of important deficiencies in the health systems of the countries, regardless of their level of economic development. In many low- and middleincome countries, the consequences of the pandemic on front-line health workers have been particularly severe due to limited resources, insufficiently funded health facilities and understaffing, a lack of skills such as self-resilience in HPs, and a lack of support from government agencies and institutions. Many of these consequences have also been observed in higher-income countries [101]. Specific factors of this pandemic have been perceptions of insecurity and fear of getting infected or infecting family members, which have directly impacted the mental health of HPs and their professional performance [ 85 , 102 ]. 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