Receipt date: 20/05/2022 / Revision date: 16/01/2022 / Acceptance date: 17/04/2023

Introduction

Coronaviruses are a family of viruses (coronaviridae) that produce a series of diseases that, generally, leave as main symptoms respiratory problems of different types, from mild as the common cold to more serious as respiratory syndrome or pneumonia. Cases such as the severe acute respiratory syndrome (SARS-CoV) of 2003 or the Middle East respiratory syndrome (SERS) in 2012 have been seen throughout history (Garcia-Iglesias et al., 2020). 

In the last days of 2019, in Wuhan, a Chinese city, several cases of pneumonia with unknown origin were detected, until several studies identified that the symptomatology had viral etiology, specifically of the coronaviridae type, with much similarity to the virus of the previously named SARS-CoV, therefore it was named SARS-CoV-2 and the disease it causes, coronavirus disease 2019 or Covid-19 (Pérez Abreu et al., 2020).

At the end of January 2020, on the 30th, the World Health Organization (WHO) declared the situation as a global public health emergency. In the course of a few months, the virus and the disease caused by it spread from a Chinese city to an important part of Europe, Italy being the first to be strongly affected, followed by Spain, continuing throughout the western area, touching the countries that seemed to be exempt and expanding to almost any territory on the Earth's surface. Following two clear criteria (1) the outbreak affects more than one of the five continents of the world and (2) the contagion and expansion of cases in each of the countries are due to community transmission (from one person to another by direct or indirect contact); on March 11, 2020, the WHO declared a global pandemic (Velavan & Meyer, 2020). 

In different geographic locations, the pandemic has evolved differently and the measures that have been put in place to curb it have been very diverse and have been implemented at different times. Despite the general recommendations given by the WHO, each country has been free to manage the situation according to its resources and requirements, so that different measures have resulted in different consequences. For example, in Spain, the country from which this systematic review is being drafted, a state of alarm was decreed on March 14, 2020 due to an extreme health situation, on which date strict home confinement began until the beginning of May, a situation that affects all Spaniards, with the exception of essential service workers, only for the performance of their work duties. Other countries, such as Sweden, did not take this measure, but the changes in the day-to-day life of citizens have also been and are significant. 

Even so, at the international level and despite the diversity of methodologies to curb the impact on the health of the population, there have been consequences for everyone, whether at the economic, social or health level (García-Iglesias et al., 2020). 

With the slowdown of the world due to the change of priorities, industries reduced or even stopped the production of their products and had to stop international marketing, with all this, sales were reduced, the fall of oil, the mismatches in the stock market, the closure of many companies in all types of sectors, the loss of employment of millions of people throughout the world, etc. In addition to all this economic reduction, there was also an increase in healthcare costs, a situation that aggravated the problem. On the other hand, changes are also observed at the social level, both those related to the economic issue and those produced by social distancing in the course of the pandemic or the isolation resulting from the measures to combat the virus, which has a very great impact on society in general, since human beings are social beings.

The most critical part of this situation is the consequences on health, but not only on physical health as the most obvious part of the problem, but also on mental health derived from the situation and concern at a general level and cause of the preventive measures against the contraction of Covid-19. The first to be hit by the pandemic, those affected by the disease and those fighting against it, such as health personnel, were particularly affected, the latter being constantly exposed to the risk of contagion, in many cases, and especially at the beginning, without having the necessary equipment to protect themselves and prevent infestation. In addition to the increase in the workload and hours of their working day, the fear of their own and their families' contagion, as well as the rejection and discrimination they have received and still receive from others due to the possibility of being carriers, has added an extra burden to the situation and has generated adverse consequences for the psychological health of these people (Ribot Reyes et al., 2020). 

As mentioned above, at a general level, the differences in the measures and restrictions, and the perception of the state of the situation, lead to the observation of different problems, but common patterns are also found. Several studies developed during the hardest months of the pandemic, and presented in this review, show changes in the psychological state of the population, as seen in variables such as stress, anxiety, sadness or even depression. 

Concern about the general health situation, fear of contagion of the disease itself or its transmission to people in the close circle such as family members, particularly those at high risk; the feeling of loneliness derived from the preventive measures for contracting the virus; the uncertainty about the economic future worldwide and in particular of each person and their relatives, or the suffering caused by the socioeconomic consequences of the situation, are factors that can contribute to the psychological state and health, such as the generation of sadness or decrease in mood, leaving in its wake more symptoms such as change in appetite (increase or decrease), sleep disorders, changes in normal circadian rhythms, etc. Difficulties have also been observed in falling asleep, maintaining sleep, or at the opposite pole, sleeping much of the day (Galindo-Vázquez et al., 2020). All this, coinciding with the symptoms of a disorder already quite prevalent in the world population such as depression (Ariapooran et al., 2021). In January 2020, WHO estimates that more than 300 million people worldwide were suffering from it. 

This widespread problem, characterized by changes in mood and emotional responses to different circumstances, is the leading cause of disability worldwide (Calvó, 2020), and although its severity varies, the worst cases can lead to thoughts, self-harming attempts or finally completed suicide. There are many risk factors for developing this problem, or at least for some of its symptoms to manifest themselves, among them are having a history (having suffered a previous depressive episode or having a family member who has suffered the problem); alcohol or drug abuse, the consumption of a specific drug; having suffered a trauma (situation of abuse, mistreatment, etc.), death of a loved one; suffering from serious and/or chronic illnesses, relational problems, exposure to continuous stress, i.e. over a long period of time; loneliness or feelings of loneliness; conflictive and uncertain situations in the environment, which would include loss of work, restrictions at a general level, etc (Lugo et al., 2018). 

As can be seen, many of the risk factors for the development of depression have appeared in the lives of a large number of people caused by the global pandemic situation we are facing, so it is of great interest to study the phenomenon, since, as described above, the consequences can even be lethal (Galindo-Vázquez et al., 2020). 

In recent months, the number of published studies related to the psychological effects left in its wake by the situation has been massive, specifically on the relationship with depressive problems. In spite of this, the information still does not clarify the doubts, since the excess of different data in such a short period and with such diverse samples generates confusion, making it difficult to organize knowledge and consensus among professionals. 

Given the relevance of the subject as an extremely topical issue, which affects citizens at an international level due to the great impact it has, the objective of this review is to compile data on the most recent and relevant publications on the relationship found between the current pandemic situation (Covid-19) and depression or its symptomatology, in order to clarify, synthesize and be able to conclude on common points and differences in the different types of samples studied, which will be described in the following sections. 

Methodology

Method

In the first instance, a search was carried out in the Sciencedirect and PubMed databases with the terms "Despression and Covid" as of November 10, 2021. The results obtained in the search through ScienceDirect were 1127 articles once filtered by subject: psychology and by type: research articles. In the case of the PubMed search tool, after filtering by journal articles, the number of articles amounted to 5839. The final selection of articles was based on the following inclusion criteria (1) quantitative assessment of depressive symptomatology using psychometric tools with high internal consistency, reliability and validity; (2) the sample size must be equal to or greater than 200 participants; (3) the sample subjects must have undergone a change after the pandemic situation was declared, that is, their geographic territory must have been affected by measures to curb the virus. Therefore, the studies excluded from the present review were those that did not quantitatively evaluate depressive symptomatology or were done using a tool with insufficient psychometric properties, as well as studies with sample sizes of less than 200 people, and those in which samples were taken from areas practically unaffected by the virus, that is, where the situation has been more under control and preventive measures have had little effect on the lives of citizens, were also excluded.

Once the specific characteristics had been detected, the selection was made through their order of relevance, based on the number of citations per time the article had been published, choosing 50 of them, the first 25 from Sciencedirect and the remaining 25 from the Pubmed search engine. 

Results

Participants

Of the 50 items selected, we obtained a total sample of 10,5576 people, of which approximately 34% were men and 66% were women. Most of the research has been conducted with an adult population between 18 and 50 years of age. The mean age of the total subjects was 33.6 years. However, although the majority is the general adult population, there are several with children under 18 as in the case of Cheng et al. (2021), Liu and Wang (2021), Tang et al. (2021) or Wu et al. (2021). Similarly, we also have samples with ages exceeding 50 years (Mazza et al., 2020; Van den Besselaar et al., 2021). 

Other notable characteristics of the users evaluated are that they come from various countries, such as Spain, Italy, Holland, Germany, Austria, Sweden, Greece, Russia, Bangladesh, Switzerland, Romania, China, Turkey, Israel, South Korea, England, the United States, Iran, Rwanda, Haiti, Togo, the Independent Republic of Congo and Australia. The most frequently repeated countries are China in 11 of the studies, Turkey in 5, the United States in 5 and England in 4. 

Although a significant part of the data come from the general population of the different countries, some studies work specifically with students, for example, that of Jin et al. (2021) or that of Tang et al. (2021). Others, such as Zheng et al. (2021) and Young et al. (2021) with healthcare personnel and that of Mazza et al. (2020) with Covid patients. There is also a very large sample of pregnant women, being the population studied in 10% of the articles analyzed, therefore, the variety will provide comparative richness between key groups.

Procedure

The studies selected for the systematic review conducted their surveys through online platforms such as Google Forms, REDCap or WeChat, among others. Two of them were the exception, in the study conducted with parents whose children suffer from ASD by Maniarikova et al. (2021), the surveys were generally conducted online, but in 30 cases by telephone. 

In the article by Mazza et al. (2020), participants answered the questionnaire via paper at the hospital where they were admitted for Covid. 

In general, as the inclusion criteria were broad, the technique for recruiting the sample was the dissemination of the questionnaires through social networks (snowball technique).

Tests used

In the 50 articles selected, a total of 16 tests were used to measure depression, the most commonly used being the Patient Health Questionnaire-9 (PHQ-9), which was used in 17 of the studies, followed by the short version of the Depression, Anxiety and Stress Scale (DASS-21), which was used on 6 occasions.

The Patient Health Questionnaire (PHQ-9) by Kroenke (2001) is a 9-item questionnaire for the detection of depressive disorder, as well as the detection of the level of severity, based on the criteria of the DSM-IV diagnostic manual. It has a tenth item that assesses the functional impairment caused by depressive symptomatology. Scoring ranges from 0 points to 27 points and the items are likert type with 4 alternatives (0= not at all to a score of 3=almost every day). According to the score obtained, the severity of the problem is determined: from 0 to 4, absence of the problem; from 5 to 9, mild; from 10 to 14, moderate; from 15 to 19, moderately severe; and from 20 to 27, severe (Kroenke et al., 2001). Its administration time is very short, about 5 minutes. This questionnaire has good internal consistency, with a Cronbach's alpha of .74 before treatment and .81 after (Cassiani-Miranda et al., 2021). 

On the other hand, Lovibond and Lovibond's (1995) Stress, Anxiety and Depression Scale 21 (DASS-21) is a self-report tool that assesses the emotional states of depression, anxiety and stress focusing on the previous 7 days. It is composed of 21 likert-type items with 4 response options (0 = does not apply to me at all; 3 = applies to me a lot or most of the time), with higher scores indicating greater severity. The established cut-off point for depression is 6. The estimated administration time is around 10 minutes. Regarding the reliability of the scale, in all the researches in different countries it presents good psychometric properties, as shown by Scholten et al. (2017):  all: α = .911; Germany: α = .885; Italy: α = .914; Russia: α = .890; Spain: α = .895. 

In the remaining investigations, different tools are used, such as the Patient Health Questionnaire-2 (PHQ-2), used in three of the studies, or even the complete PHQ. The Beck Depression Inventory (BDI), in its full version and also in the short 13-item version. In five other investigations, the Hospital Anxiety and Depression Scale is used. On the other hand, the Center for Epidemiological Studies Depression Scale (CES-D), the Hopkins Symptom Checklist (HSCL), the Edinburgh Depression Scale (EDS) or even the WHO Depression Measurement Scale have been used in the studies analyzed.

Results

As explained above, depression and its symptomatology is a very prevalent problem throughout the world and due to the characteristics of the pandemic situation that the world is going through and, above all, has gone through in recent months, there is a suspicion of an increase in depressive symptomatology due to the increase in risk factors for suffering from it. Most of the studies included in this review agree that, at a general level, between 20 and 40% of the population shows depressive symptoms, placing the average at 32.6%, which when compared with the general average established between 8 and 15% (WHO, 2020), a very significant increase has been observed. It is true that the prevalence is even higher in certain particular samples, as in the case of healthcare workers, with data exceeding 40%, as in the study by Mosolova et al. (2021), where its sample shows a depression rate of 45.5%. Also the research of Das et al. (2020), where 63.5% of the physicians in the sample presented depression. Another type of population that has been particularly affected are pregnant women, all studies with this type of sample have shown highly significant data, one of them in particular by exposing rates of depressive symptomatology higher than 50%, specifically 56.3% of women (Kahyaoglu and Kucukkaya., 2021).

Another study that stands out for the high prevalence of depressive symptomatology is the one conducted with the general population of several countries during the quarantine period, indicating data of 58%, the highest of those reviewed (Shah et al., 2021). Linked to this, we find agreement in several studies that the severity and extent of socially restrictive measures implemented by governments to curb the pandemic, such as home confinement, is directly related to the suffering of depressive symptoms (Perez-Cano et al.2020; Rudenstine et al., 2021; Tang et al, 2021). Shah et al. (2021) specifically showed that the more days people spent in quarantine, the higher the prevalence of depressive symptomatology.

Except for the contributions of Korkmaz and Güloglu (2021) and Tang et al. (2021), which adds contrary data, the other articles that distinguish the differences in the prevalence of depressive symptomatology in men and women show that it is the latter who have most noticed and suffered the transit through a situation of health alarm. Even before these months, women in general were more affected by this mental health problem; it is estimated that for every 10 women affected, there are 7 men. After the course of this phase, the increase for women has been more or less proportional; the general computation of the evidence analyzed here leaves some examples such as the following: 29.9% females, 20.1% males (Cénat et al., 2021); 15% females, 12.2% males (Bäuerle et al.,2020); 51.6% of females in the total sample and 45.2% of males (Rudenstine et al., 2021). 

Another particularly relevant and significant finding, due to the number of times it is repeated in most of the studies, is the relationship between age and the presence of depressive symptomatology. Evidence shows that young people are more at risk of suffering symptoms of this psychopathology, where the most at-risk ages are between 18 and 30 years, although a study which includes a large sample variety (general population of several European countries), provides striking data, and is that people aged between 16 and 25 have been even more affected (Shah et al., 2021). Only 5% of the articles reveal different data, where no difference in prevalence of depressive symptomatology related to age is observed; as a particularity of these data, it is noteworthy that it is an article that studies students with a small age range, from 16 to 27 (Tang et al.,2021). 

As for the correlations found between depression and other variables, we observed the type of preventive measures for the contraction of the virus taken by each government in the different territories studied. Proportional data are obtained between the hardness of the measures and the number of cases showing symptoms of depression. Territories facing home confinement such as Spain, Italy or China among others, show slightly higher scores with respect to those who despite having limitations, could go outside (Bäuerle et al., 2020; Fancourt et al.,2021; Fountoulakis et al.,2021; González-Sanguino et al.,2020; Shah et al., 2021).

Closely linked to the latter, the factor of physical exercise appears to be protective for depressive symptomatology, the intensity of training being proportional to its buffering capacity against the shock of the braking measures of the pandemic wave, according to the data provided by Brailovskaia et al. (2021) and Feter et al. (2021). In the case of the research by Shah et al. (2021) Kahyaglu and Kucukkaya (2021), what is seen is that there is a relationship between not practicing exercise and the presence of more depressive symptomatology. 

Another area particularly affected by the anti-Covid measures has been social relations. At a general level, the measure of social distancing has been incorporated, which has been a risk and/or aggravating factor for the development of the symptomatology studied. González et al. (2020) and Lin et al. (2020), support under evidence the great influence of this factor, with a correlation of .090, on the contrary, none of the researches rule out the relationship. 

As has been mentioned and occurs with other important elements, the degree of restriction of the measures aggravates or alleviates the consequences, in terms of social distance, it is in cases of home confinement where more interproblematic relationships are found, that is, people isolated at home for a period of time have developed more depression than those who in a controlled manner have been allowed to establish interpersonal contact beyond the cohabitants. More in depth, the research of Shah et al. (2021), adds that the most affected have been people in confinement, living alone, especially separated/divorced or widowed, followed by those living in households without children. These data have been associated with factors such as self-efficacy, resilience and psychological flexibility with correlations of .053, .071 and .090 respectively (Gonzalez et al.,2020; Lin et al., 2021).

Another element strongly associated with depressive symptomatology during the Covid pandemic, strongly evidenced by the present studies, is the presence of fear in people. We observed that fear of the virus contraction itself is present in an average of 30% of people who present depression after this period. Even higher percentages were obtained in some studies that included a healthcare population, as in the case of Gainer et al. (2021), with 39.5% or the Kang et al. (2020) with 34.4%. On the other hand, data reaching 45.5% in Haitian women exposed to Covid and with fear of contagion stand out (Cénat et al., 2021). 

On the other hand, the uncertainty left by all the circumstances experienced with the wave of contagions and the slowdown of activity at international level, has brought with it doubts and uneasiness about what will become of the economy, both in general and in particular. González et al (2020), Lebel et al. (2020) and Shah et al. (2021) show us how those with higher monthly incomes score lower on tests assessing depressive problems. The fear of work conflict, lack of adaptation to the new telework and finally dismissal, is highly correlated with the suffering of signs of depressive psychopathology, for example, the research of Feter et al. (2021) shows a correlation of .730 between these two factors. 

Discussion

During the last few months, practically the entire geography of the world has been involved in a completely extraordinary situation for which it has become quite clear that we were not prepared. At the end of December 2019, in Wuhan, a Chinese city, the first cases of people affected by an unknown virus that caused a disease with diffuse symptomatology attacking mainly the respiratory tract appeared in Wuhan (Cruz et al., 2020). With the passage of a few weeks, this virus seemed to begin to spread across the map, even without being aware of how dangerous it is for health, the world continues with its normal rhythm until it reaches with force the western society, such as Italy and Spain, causing collapses in the health system due to thousands of contagions in record time. As a result of this health emergency, the various governments began to take drastic measures, including various restrictions on the course of daily life, in the strictest cases even including the confinement of the population to their homes. 

As could be expected, the set of events as unusual as sudden and intensely experienced, has resulted in the emergence of a wide variety of consequences for the terrestrial population, whether at the economic level, due to the stoppage of industry, product marketing, etc. At the social level, due to the measures necessary to stop the massive contagion of the virus, since it has been seen that the easiest and most common contagion of the virus is in cases where the virus carriers remain at a distance of less than one and a half meters (without a mask) for more than 15 minutes (the saliva droplets will carry the viral load) (Pinzón, 2020). Or at the health level, beyond the physical ones, we focus on the psychological ones resulting from all of the above and the measures put in place to curb the wave of contagions. Specifically, it is noteworthy what influence it may have had on the appearance of depressive symptomatology, since everything described above would be a risk factor for the generation of this psychopathology (Huarcaya-Victoria, 2020). 

When researching scientific publications on the subject, one discovers an enormous amount of content and data, which due to its research and publication so quickly because of the need and topicality of the problem, remains unclear, therefore, the overall objective of this review has been the analysis of existing information on the impact in terms of what depressive symptomatology refers, which has left the situation experienced by citizens of the world because of a viral outbreak that has crossed borders; differentiating between gender groups, ages, geographical location and other situations in addition to specific risk factors. Specifically, it is important to distinguish those groups or profiles that are most affected, in order to clarify and determine them. 

As it has been observed after the analysis of the variety of data, it is concluded in a very generic way (since this issue is detailed in the previous section of results), that at general levels, the people who have been most affected are young people, worsening in the case of women and above all having been in a situation of home confinement without an outside space to go to during that period of time, people who have not done physical exercise and whose socioeconomic status is medium-low. On the other hand, in addition to the harm, students and those who have been more active during the strongest months of the pandemic, such as health care workers, have shown higher levels of depression, either because of the psychoemotional burden it entails and/or the fear of contagion due to exposure. 

This approach will allow clarifying the knowledge on the subject at present, so that with the conclusions obtained, the relevance of the subject can be made known within the scientific culture, and in the future it will be taken into consideration in new research. On the other hand, another of the practical implications of the review lies in using the data to intervene, for example, by proposing coping strategies for the problem both at a general level (since an increase in the problem has been observed) and for the different more specific groups that have been particularly affected (women, young people, inhabitants of countries with stricter measures, sedentary people, etc.). Specifically, it could begin by using the data as scientific support to begin to give visibility to the importance of mental health as an essential component of people's overall health, the methodology could be through public media such as television, or information within the visual reach of all, for example, advertising posters in places of common transit among citizens (health centers, public service buildings, etc.), providing citizens with the necessary knowledge to identify warning signs of problems of psychological causality.

Providing objective data on the general increase in depression, we would also propose the expansion of psychological consultations in the public health system, including the creation of the figure of the "bedside psychologist", in order to be able to reduce the new massive problem. In connection with the latter, with sick leave due to depression being one of the most common in Spain (INE, 2021), investing resources in the treatment of depression could reduce the economic cost it generates for the state. 

Another practical implication would also be to consider the passage through the pandemic situation, specifically home confinement (deprivation of freedom and contact with the outside environment) as a new risk factor for the development of depressive symptomatology.

As for the limitations, we can highlight both those inherent to the systematic review and those observed in the original articles analyzed in it. Firstly, and as a first limitation of the present review, it should be pointed out that only articles in English were used, discarding those that, despite meeting the inclusion and exclusion criteria, did not show an English version. Another limitation would be to include 50 articles from only two search engines, in this case ScienceDirect and Dialnet, which could have omitted relevant information unintentionally. 

As for those observed in the original studies that made up the review, the limitations lie in some of the sources of information used to contextualize and base their studies, since the subject matter is so current that previous support is minimal or non-existent. Another limitation is the method used to obtain information, since almost all the articles use the online survey, which may mean that older people have not agreed to respond because their use of new technologies is generally inferior. The use of the snowball method, which prevails in the selected evidence, could have left an important part of the population out of the evolution, thus producing a selection bias. 

Given the limitations highlighted and the obtaining of the data observed, several lines of future research can be suggested, firstly, the study of other possible consequences at the psychological level that the pandemic period (with its particularities as previously described) has provoked in the general population. It is also of interest, and the field remains open, to investigate the factors that make the more specific groups of people who have been affected particularly vulnerable, factors beyond the perhaps more obvious ones such as those discussed here. 

On the other hand, the idea of conducting research using several survey modalities is raised, since taking into account that the use of online procedures may limit the number of elderly participants, the data may be biased.

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Annex 1

Table 1

Reviewed articles

Article	Sample	Instruments	Procedure	Results
Akgor et al. (2021)	N= 297 M= 27,64 Men=0 Women=297	HADS	Online Questionnaire	Increased depression, correlated with fear of infecting themselves and their babies during childbirth. Difficulty of contact with medical personnel predictive of depressive symptoms.
Ariapooran et al. (2021)	N=315 M=34,69 Men= 120 Women=195	BDI-13, BAI, BSSI, SI, STS.	Online Questionnaire	51.11% Symptoms of traumatic stress. Twice as many people had depression if they had traumatic stress. More common in women and emergency nurses.
Armour et al. (2021)	N=1989 M= ? Men= 597 Women= 1392	GAD-7, PHQ-9, LEC-5, UCLA, MLQ, Social support	Online Questionnaire	Increased rate of depression in the general English population. Risk factors: lower sense of life and loneliness.
Bäuerle et al. (2020)	N=15037 M= ? Men= 4353 Female=10633	GAD-7, PHQ-2, DT	Online Questionnaire	Depression rate of 14.3%, younger women more predisposed.
Brailovskaia et al. (2021)	N=1931 M=26,87 Men=433 Women=1498	DASS-21, physical act., load per covid	Online Questionnaire	Increased depression after confinement. Physical exercise cushioned the impact.
Cénat et al. (2021)	N= 1267 M=32 Men=750 Women=517	HSCL, CD-RISC2	Online Questionnaire	Average rate of depression: 24.3%. risk factors were younger, female, exposed to Covid and dissatisfied with work.
Ceulemans et al. (2021)	N=9041 M= ? Men=0 Women=9041	EDS, GAD-7, PSS	Online Questionnaire	15% of pregnant women and 13% of breastfeeding mothers suffer from depression.
Cheng et al. (2021)	N=1595 M=14.16 Men= 707 Women=888	IES-R, CES-D, SIOSS	Online Questionnaire	Stressful situational events Covid correlates positively with depression. Parent-child communication as a protective factor.
Cordos and Balboac. (2021)	N=402 M= Men=199 Women=283	OMS-5, GAD-7, SME	Online Questionnaire	There is no increase in depression related to the use of social networks to obtain pandemic information. There is no relationship between age and depression.
Das et al. (2020)	N=422 M=27.61 Men=234 Women=188	PHQ-9, DSS	Online Questionnaire	63.3% of the physicians showed signs of depression. Women and apprentices have a higher incidence.
Fancourt et al. (2020)	N=36520 M= Men= 8821 Women= 27699	PHQ-9, GAD-7	Online Questionnaire	After the first week of confinement, the depressive symptomatology increased considerably: 27% mild, 13% moderate, 5% severe. After 20 weeks it decreased.
Feter et al. (2021)	N=2321 M= Men=543 Women=1778	HADS	Online Questionnaire	Moderate-severe depressive symptoms have increased from 3.9% to 29.1%.
Fountoulakis et al. (2021)	N=3399 M=35.2 Men=621 Women=2756	Ad hoc.	Online Questionnaire	Of these, 9.31% had clinical depression, 21.1% had relapsed and 8.96% had their first depressive episode.
Gainer et al. (2021)	N= 1724 M= Men=750 Women=959	PHQ-9, GAD-7, APCL	Online Questionnaire	39.5% above the cutoff on PHQ-9, COVID exposure negatively influenced the development of depression, anxiety and PTSD. Higher risk in women and in young people between 26 and 30 years of age.
Gonzalez- Sanguino et al. (2020)	N=3480 M=37.92 Men=870 Women=2610	PHQ-2, PCL-C-2, GAD-2, InDI-D, UCLA, EMAS, FACIT-Sp12, SCS	Online Questionnaire	Receiving information about Covid is a protective factor for the development of depression. Being a woman, young, with economic scarcity or insecurity and loneliness are risk factors.
Gundogmus et al. (2021)	N=2460 M=32.65 Men=823 Women=1637	DASS-21	Online Questionnaire	Increased depression with each peak/wave of the pandemic. The rate varies according to economic income and lifestyles.
Hammarberg et al. (2020)	N=13762 M= Men= 3328 Women= 10434	PHQ-9, GAD-7	Online Questionnaire	Difference in the rate of depression between men (20.1%) and women (26.3%). Having a previous health problem is a risk factor.
Hyland et al. (2021)	N=2061 M= Men= Women=	PHQ-9, GAD-7, BFI, BRS, LOCS, IWA+IS, DAIS, IUS, PHQ-15	Online Questionnaire	Less depression after pandemic , no change in major depression after confinement.
Jin et al. (2021)	N=847 M= Men= Women=		Online Questionnaire	Current depression rate in Chinese university students is 29.16%.
Jung et al. (2021)	N=1928 M= Men=680 Women=1248	GAD-7, PCL-5, PHQ-9, UCLA, CD-RISC-10	Online Questionnaire	People with previous depression, relapse. Social support acts as a protector. More in men.
Kahyaoglu and Kucukkaya. (2021)	N=403 M=28.2 Men=0 Women=403	HADS	Online Questionnaire	Depressive symptoms in 56.3% of the sample. Influencing factors to be highlighted are educational level, smoking, sedentary lifestyle and chronic disease.
Kang et al. (2020)	N= 994 M= Men=144 Women=850	PHQ-9, GAD-7, ISI, IES-R.	Online Questionnaire	34.4% suffer mild alterations, 24.4% moderate and 6.2% severe. Significant correlation between depression and direct exposure to Covid.
Kimhi et al. (2021)	N= 804 M=43.84 Men=416 Women=388	BSI	Online Questionnaire	Religiosity is a buffering factor for the development of depression in the face of Covid situation
Korkmaz and Güloğlu (2021).	N=426 M=37.40 Men=163 Women=263	IUS, MLQ, BDI, BAI	Online Questionnaire	Depression rate of 13.9%. Tolerance to uncertainty correlates positively with depression. There are no differences between genders.
Lebel et al. (2020)	N=1987 M=32.4 Men=0 Women=1987	EPDS, SSEQ, Physical Activity, Anxiety by Rini et al.	Online Questionnaire	37% of pregnant women showed depression. There is a correlation between depression, fear of covid infection and other secondary consequences of the situation.
Lin et al. (2021)	N=751 M=30.51 Men=0 Women=751	SAS, PHQ-9	Online Questionnaire	Younger age, higher education, sedentary lifestyle, situational uncertainty and having Covid symptoms, predictors of depression.
Liu and Wang. (2021)	N=617 M=13.11 Men=326 Women=291	CPSS-19, GHQ-20, VIA	Online Questionnaire	Perceived stress from the pandemic situation correlates with depression.
Maniarikova et al. (2021)	N=268 M=42.66 Men=134 Women=134	HADS	Online Questionnaire	Increased depression in fathers and mothers with autistic children associated with their behavioral change.
Mazza et al. (2020)	N=402 M=58 Men=265 Women=137	IES-R, PCL-5, BDI-13, STAI-Y, MOS-SS, WHIIRS	On-site Questionnaire	Increase of more than 10% in depression rate.
Mosolova et al. (2021)	N=2195 M=34 Men=713 Women= 1482	SAVE-9, GAD-7, PHQ-9, MBI, PSS-10	Online Questionnaire	Significant increase of depression in health care workers (45.5%). The most at-risk profiles are women, young people and medical graduates.
Nikčević et al. (2021)	N=502 M=39.3 Men=268 Women=234	BFI-10, WI-7, CAS, C-19ASS, PHQ-ADS.	Online Questionnaire	Directly proportional relationship between extraversion, agreeableness, conscientiousness, neuroticism and depression.
Pérez-Cano et al. (2021)	N=613 M=26.77 Men=147 Women=466	DASS-21, STAI	Online Questionnaire	41.3% Depressive symptoms.
Rudenstine et al. (2021)	N=1821 M=26.17 Men=493 Women=1301	PHQ-9, GAD-7	Online Questionnaire	Depression was present in 50.3% of the sample. Women and young people are more likely.
Shah et al. (2021)	N=678 M= Men=290 Women=388	DASS-21	Online Questionnaire	Women between 18 and 24 years of age are the most affected. Family support, the practice of exercise and fewer days in quarantine favor the cushioning of the problem.
Tang et al. (2021)	N=4342 M=11.86 Men= 2216 Women= 2126	DASS-21	Online Questionnaire	Depression increased overall among Chinese students. The most affected were those facing selectivity.
Tang et al. (2020)	N=2482 M=19.81 Men=960 Women=1525	PCL-C,PHQ-9, Sleep	Online Questionnaire	Predictors: sleep less than 6 hours, last university course, extreme fear of Covid, lives in an area highly affected by Covid. Non-predictors: age, duration of quarantine and being an only child or not.
Tasnim et al. (2021)	N=971 M=42.3 Men=486  Women=485	GAD-7, PHQ-9	Online Questionnaire	Depression rate at time of measurement: 39,9%. Risk factors: female, student, poorer quality of life, medical illness and pathological comorbidity.
Tsang et al. (2021)	N=1464 M=52.8 Men=368 Women=1096	PHQ-2, Ad hoc fear.	Online Questionnaire	Fear of Covid as a predictor of depressive symptomatology.
Van den Besselaar et al. (2021)	N=1068 M=73.8 Men=504 Women=564	CES-D, HADS-A, MMSE,LASA FI, Pearlin Domain	Online, paper and telephone questionnaires	The rate of depression was affected, general increase.
Voitsidis et al. (2021)	N=2752 M= Men=697 Women=2055	IUS-12, FCU-19s, PHQ-9	Online Questionnaire	41.1% mild, 18.2% moderate, 4.5% mod-severe and 0.5% severe depressive symptoms. Fear of the virus as a mediating factor.
Wathelet et al. (2020)	N=69054 M=20 Men= 18803 Women= 50251	IES-R, STAI-Y, BDI-13	Online Questionnaire	16.1% showed depression. Women were significantly more affected.
Wu et al. (2021)	N=1825 M=12.7 Men= 1067 Women=758	MMHI-60	Online Questionnaire	More depression in those who suffer new psychotic experiences.
Yigitoglu et al. (2021)	N=435 M=36.76 Men=191 Women=244	PSQI, HADS	Online Questionnaire	Increased depression among hospital personnel. There is no difference between positions, but women suffer from it more frequently.
Young et al. (2021)	N=1685 M= Men=353 Women=1096	PHQ-9, GAD-7, PC-PTSD, Alcohol use	Online Questionnaire	29% present mild symptoms, 17% moderate-severe.
Zheng et al. (2021)	N=617 M= Men=3 Women=614	KAP, DASS-21	Online Questionnaire	Depression rate of 15.4%.   Direct exposure to Covid