In 2020, the world faced one of the most significant pandemics of the last two generations. Every day around the world, thousands of people are dying, and hundreds of thousands are becoming infected with this new coronavirus characterized by its highly contagious nature [1]. In humans, usually causes respiratory infections that can range from a common cold to severe illnesses such as the Middle East respiratory syndrome (MERS) or the severe acute respiratory syndrome (SARS) [2]. The recent discovered coronavirus (Sars-CoV-2) has caused the pandemic (COVID-19), with greater ratio of mortality and contagiousness than its predecessors ^[2][3][4][2,3,4] However, it is not only the health effects that are of concern regarding the virus and the current pandemic.

The rapid transmission of the virus [5], has left governments and institutions around the world in check, among Asia to Europe, North America, the Middle East, Africa, and Latin America ^{[6][7][8][9][10]}[6,7,8,9,10]. Most of the countries took prompt and promising measures to prevent the contagion from spreading, such as closing borders, pre-emptive isolation, and quarantine [11]. However, despite these measures have slowed down the speed of transmission have also had a severe impact on their economies and societies ^[12][13][12,13]. Economically, the impact on jobs stability [8]; Socially, highlighting and opening a greater gap between class differences and social spectra specially among vulnerable and hidden groups such as ethnic communities, minority groups, immigrants and homeless ^{[8][14][15][16][17][18][19]}[8,14,15,16,17,18,19]. Culturally, highlighting the need for virtualization of educational environments in order to materialize distance education [13], which has remarked inequities in rural and low income areas ^[20][21][22][20,21,22].

This impact on health and the social and economic sphere has a direct impact with psychological distress and symptoms of mental illness ^[23][24][25][23,24,25]. Despite the existing literature, which may need to be filled in over time through more widespread clinical experience and research, authors are beginning to identify the first mental health concerns related to the COVID-19 pandemic, which are stress, experiencing episodes of anxiety and depression, alcohol consumption, eating disorders, hunger, and uncertainty about the future, among others [26]. Some authors found traumatic experiences related to the loss of friends and family, work stressors, social status, and suffering from COVID-19 symptoms [5]. Conditions such as anxiety, depression, insomnia, or other social problems such as increased acts of gender violence during the lockdown, could increase short term mental health care needs ^[27][28][29][27,28,29]. A global pandemic that has caused nearly 10 million people to become infected and more than half a million deaths would probably lead to, like other disasters (e.g., Hurricanes, tsunamis, wars, terrorism), post-traumatic stress disorder (PTSD), insomnia, generalized anxiety disorder and fear ^[26][27][26,27]. Therefore, psychologist and psychiatrist worldwide across the world should be aware of these manifestations, and be prepared for what its believed the “post-pandemic wave”, the mental health consequences of COVID-19. In this situation mental health services, conceived as all services that integrate care in the promotion, prevention, treatment and rehabilitation of mental problems and disorders, including psychiatric hospitalization, outpatient consultation, dispensing of drugs for psychiatric and neurological use, are basic to be able to face this new demanding context. Thus, the current review was designed to summarize the existing literature addressing mental health concerns related to the COVID-19 pandemic and the measures taken by governments worldwide.

2. Search Methods and Strategies for Identification of Studies

Protocol was based on a literature search using primary sources, such as scientific articles and secondary ones, such as bibliographic indexes, web pages, and databases. Thus, we used PubMed, Scopus, Embase, Science Direct and Web of Science using MeSH-compliant keywords including COVID-19, Psychology, Mental Health, Coronavirus 2019, SARS-CoV-2 and 2019-nCoV.Articles published from 5 February 2020 till January the First 2021 were used. For inclusion criteria nine review authors screened the titles and abstracts of all retrieved manuscripts, then exclusion criteria were applied if (i) studies used old data (out of the proposed timeline), (ii) had inappropriate topics and were not pertinent to the focused purpose of the study, (iii) were not in English. Extraction of information was performed by the same nine review authors who conducted the study selection. Then, studies were selected independently, and the results were discussed to make the present narrative review.

3. Psychophysiological Stressors in the COVID-19 Pandemic

Psychophysiology is one of the cornerstones of clinical health psychology, and its primary objective is to understand how psychological and social experiences could influence an individual’s physiological homeostasis. During the current COVID-19 pandemic, a holistic perspective is needed since isolation measures, fear, uncertainty, economic instability, social disconnection and trust in other people and institutions are becoming new psychophysiological stressors [28]. Fear may be one of the strongest triggers. Fear of contagion, but also fear of the future, of losing their job in professions in which they cannot work from home. Fear of not having enough financial resources to be able to pay their normal bills. Fear of the uncertainty of not being able to see relatives. Fear of how the virus is transmitted. Maybe the worst fear: will I be infected? Will I be infecting my loved ones without knowing it? Will I be part of the asymptomatic population helping the virus to spread? [29]. This stressful and novel situation would lead to psychological consequences in the medium and long term [30].

Physiologically, acute fear may not have negative health implications but when it is prolonged over time, changes occur in the immune and autonomous nervous systems, endocrine function, and level of hyperarousal, in addition to sleep/wake cycle disruption, eating disorders and dysregulation of the hypothalamus-pituitary-adrenal axis [31]. Recent studies suggest how psychological stress may also increase the production of hypothalamic and amygdala corticotropin-releasing hormone (CRH), which has been recognized as a precursor of cortisol production [32]. CRH has been shown to have an impact on mucosal mast cells, increasing the production of inflammatory cytokines and tumor necrosis factor-alpha (TNF- α), which directly affects gut epithelial cells, increasing gut permeability. These physiological conditions do nothing but increase the severity and fatalities associated with the COVID-19 pandemic [33].

Other contextual factors that may increase comorbidities among the population are related to physical inactivity due to an imposed quarantine, which even before the COVID-19 pandemic, was already a major global health problem [34]. Since quarantine is a long-term suppression measure, metabolic syndromes may appear or become aggravated, increasing the risk of insulin resistance, oxidative stress, inflammation, obesity, endothelial dysfunction, and cardiovascular disease [35]. This limitation of movement will lead to more sedentary activities, which authors propose will not only reduce energy expenditure but also increase food intake as these tasks decrease feelings of satiety and fullness, and lead to overconsumption, thus worsening the metabolic effects of sedentary behaviors [36]. In this situation, there is an increased level of pro-inflammatory cytokines and downregulation of hormones such as serotonin and melatonin, which are highly important for maintaining circadian rhythms since night-time melatonin derived from the pineal gland is the primary driver of night-time immune cell dampening which occurs as part of the circadian rhythm [37]. Thus, there should be a particular focus on appropriate behaviors as well as physical and nutritional guidelines adapted to the new situation.

4. Social and Work Stressors in the Pandemic

In the fight against the COVID-19 pandemic, until we have achieved herd immunity with an effective and safe vaccine, the behavior of world’s population plays a crucial role in stopping the spread of the virus [15]. The current perspective on coping with the pandemic is limited to the impact on physical health and minimizing transmission risks (i.e., masks, social distancing, frequent hand washing). This approach distracts attention from the psychological consequences of social stressors [38]. In this line, authors suggested that most of world’s population did not consider confinement to have an impact on general mental health. The inappropriate behaviors of some people (i.e., mass gatherings, coughing without covering their mouths, physical contact…) aggravated the Spanish flu pandemic that led to more than 50 million deaths [39]. Today, mass media and government communication systems could be an excellent way to improve prevention and increase social confidence [40]. However, fake news (e.g., consumption of hydroxychloroquine, sodium chlorite, antibiotics, conspiracy theories) and political power struggles have controlled social networks and TV programs along with the pandemic and, consequently, have increased distrust and insecurity ^{[41][42][43][44]}[41,42,43,44]. Furthermore, growing concerns about the socioeconomic impact, possible second waves and market uncertainty are major social stressors, and their long-term effect has not been studied yet. The socioeconomic crisis derived from the COVID-19 pandemic could have a significant impact on world gross domestic product, equal to about 20 trillion dollars, with 3 to 15% decreases depending on the country [8].

In addition, the unpredictable global financial consequences and the local socioeconomic impact will have devastating effect on jobs and the socioeconomic balance of individual households. Quarantine, a drop in consumption, business closures and restrictions on tourism have affected the most important stock indices ^[45][46][45,46]. Travel restrictions not only affected jobs related to air transport (i.e., loss of between 25 and 30 million jobs and the bankruptcy of dozens of airlines) but also caused general population consumption dynamics to decrease by 25 to 30% [47]. This abrupt drop in consumption has produced massive job loss, which could be permanent in more than 40% cases. Some multinational companies have advised employees to transfer their work to other productive sectors in anticipation of falls of more than 90% in terms of hiring workers [46]. Several publications have suggested that employment losses and changes to the business world have had devastating effects on mental health and suicides [48]. Job loss was especially traumatic among the most vulnerable populations (e.g., people at risk of poverty, experiencing race or gender-based discrimination, with few academic qualifications) and there are compelling proposals for prevention and protection in terms of physical and mental health requirements [49].

Yet, pandemics rarely affect everyone equally, so official interventions must be properly designed and well-adjusted. Differences in gender (e.g., PTSD, hyperactivation of the arousal system and cognitive disturbances affect females 7% more than males), race or social status demand the same level of intervention during and after the COVID-19 pandemic [50]. Gender violence [51], higher stress levels in pregnant women [52], higher risk of infection among ethnic groups [17], different mortality levels per race [53] and suicides among impoverished social groups [54] encourage new political decisions to look for competent and free interventions in terms of general mental health. Most socially vulnerable people are at risk of considering the COVID-19 pandemic to be a lifetime traumatic experience [55]. Some authors believe that the COVID-19 crisis should be faced from the perspective of trauma, threat, and fear, with special attention paid to young people who are less able to develop positive coping strategies [56]. Additionally, people with fewer academic qualifications, low social status groups, and gender differences must be cared for quickly and adequately to prevent future mental illness [57].

Finally, focusing on the social and working related circumstances of those who are on the front lines dealing with the virus, health workers, they require special attention. Health workers are a high-risk group from a mental health perspective. Early care programs to reduce work stress could help to control PTSD in hospital settings ^[58][59][58,59]. Positive coping strategies, emotional moods, social support, burnout, and personal wellbeing during the pandemic should be studied in-depth in these workers [60]. All those studies would allow the detection, diagnosis and treatment of insomnia, depression, anxiety, burnout, and PTSD cases, reducing undesirable mental health problems in front-line and intensive care unit workers ^[29][61][29,61]. Improving sleep patterns, rest and moods would help in clinical decision-making during critical times such as when there is an influx of infected people and implementing COVID-19 treatments [26]. Hence, an excellent strategy to find the best intervention for mental health must be designed to reduce long term effects on the most vulnerable populations. The main psychosocial and work stressors during the COVID-19 pandemic, such as fear, co-workers’ deaths, psychological anguish and frustration due to a lack of effective treatments, produced higher PTSD levels in front-line healthcare workers compared to non-clinical personnel [44].

5. Contextualization of COVID-19 Numbers and Measures Adopted Worldwide

The first reported case of COVID-19 was in December 2019 in the city of Wuhan, the capital of Hubei (China). From that point on, confirmed cases spread across the world until the World Health Organization declared it a global pandemic on 11 March. To date, 7.6 million people have been infected with COVID-19, with the United States of America being the country with the most confirmed cases worldwide: more than 2 million (2,032,524). Brazil is the second country worldwide where cases are growing exponentially (828.810). In Europe, at present, there are 2,316,910 confirmed cases: 292,954 in the United Kingdom, 243,209 in Spain, 186,022 in Germany, and 152,067 in France, among others with a high number of cases. Portugal has been included in Table 1 as an individual case since it is next to Spain and has reported less than 37,000 cases [62]. China has reported 84,729 confirmed cases and 4645 deaths. Moreover, while most countries are in the process of easing restrictions, COVID-19 has taken 426,317 lives worldwide, 114,466 in the United States alone, followed by Brazil with 41,828 deaths. In Europe, daily deaths have slowed down but are still considerable. 41,481 in the United Kingdom, 34,233 in Italy, 29,312 France, 27,136 in Spain 8781 in Germany, and 1505 in Portugal [63].

Depending on the socio-economic and cultural circumstances, governments have taken internal actions to tackle the situation and face the “COVID-19 challenge”. Without the presence of a vaccinated population, most countries are doing their best to lessen the spread, whether by temporary lockdown, easing restrictions in stages, or carrying out fast and easy-to-take coronavirus tests. Table 1 lists the measures adopted by country to recover normality and at the same time prevent the spread of the disease.