The COVID-19 pandemic, which emerged in Wuhan, China, has rampantly spread to various countries, territories, and areas globally and has been one of the most serious pandemic over more than 100 years following the influenza pandemic in 1918 (1). Apart from the burden on the healthcare industry, the COVID-19 pandemic has significantly affected the economy worldwide (2). In response to the socio-economic burden caused by this pandemic, governments in many countries launched policies and guidelines quickly in order to ascertain control over this pandemic (2). In the absence of any definitive treatment and vaccination available against SARS-CoV-2, the causative organism; health officials and organizations worldwide have asserted the necessity of non-pharmacological interventions with imposition, if indispensable to ascertain control over the ongoing pandemic (3). Some of these non-pharmacological interventions included social/physical distancing and lockdowns with isolation of COVID-19 positive and suspected COVID-19 patients, quarantine of exposed individuals, travel limitations, closure of educational institutions and workplaces, prohibition of mass gatherings, rapid testing, proper allocation and use of personal protective equipment and maintenance of personal hygiene (3, 4).

In China, particularly in Hubei province, early measures taken by the government consisted of rigorous lockdown with travel restrictions, and social distancing measures. Other measures included rapid case detection with immediate isolation and quarantine measures for the infected and suspected cases with medical observation for all the contacts. These measures have had a positive impact on controlling the COVID-19 outbreak (4–8).

The combined non-pharmacological interventions had a substantial effect on the reduced transmission of COVID-19 across China (4). Similarly, Vietnam, which was the first nation to delineate human-to-human transmission outside China, successfully controlled the outbreak using extensive control measures without enforcing a strict lockdown (9). Vietnam instituted rapid isolation and detection of primary and secondary cases and immediate quarantine of their contacts to curb transmission. Suspected cases in Vietnam were recognized and quarantined based on their epidemiological risk of infection. In Vietnam, more than 200,000 people have been quarantined for 14 days (10). Thus, non-pharmaceutical interventions have been very effective in controlling the COVID-19 pandemic. Such non-pharmaceutical interventions have also affected the mental health of people worldwide. A recent study done on 1,784 school students in China, showed that closure of schools as a part of lockdown and social distancing guidelines affected the mental health of the students with a slightly increased prevalence of depressive and anxiety symptoms (11). Another study done on healthcare workers in Italy showed that they experienced increased symptoms of depression, post-traumatic stress symptoms, insomnia, and perceived stress (12). These findings are in congruence with the past pandemics such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) (13–15). Amongst the non-pharmaceutical interventions, quarantine and isolation have been found to be the most associated with significant psychological impact (16). Quarantine and isolation both involve separation from loved ones, lack of freedom, and boredom which can affect mental health as seen in the past pandemics (16). A study done on 170 people who were self-isolated at home during the COVID-19 outbreak in China showed that anxiety and stress of isolated individuals were at higher levels and quality of sleep was low (17). However, there is a paucity of evidence quantifying perceived stress and peoples' coping strategies adopted during confinement periods in isolation/quarantine facilities globally. Understanding of the perceived stress and coping strategies adopted by people is important for contemplating the consequences of a pandemic on mental health of people globally. The findings can help health officials in drafting policies and implementing targeted measures to reduce psychological trauma faced by quarantined/isolated people during a pandemic. In this study, we intended to assess the perceived stress status of quarantine/isolation globally during the COVID-19 pandemic and examine the various correlates involved in dealing with the perceived stress.

We examined the various factors attributed to stress among individuals who were quarantined or isolated during the COVID-19 pandemic through our survey. There appeared to be a strong correlation between the number of days spent in quarantine and the PSS score, with a calculated risk of 0.7% increase in the PSS score with each additional day of quarantine. The impact of the duration of quarantine on mental health has been studied previously, particularly during the SARS outbreak, which demonstrated that prolonged quarantine periods were associated with symptoms of post-traumatic stress, anger, avoidance behavior, and overall poor mental health (19–21). In their study during the early days of the COVID-19 pandemic, Lu et al. (22) observed a similar relationship between quarantine duration and anxiety/depression by monitoring the activity of quarantined individuals on their Twitter accounts. The authors collectively analyzed 214,874 tweets from 1,278 quarantined individuals and 250,198 tweets from 1,278 individuals who served as controls. Besides, they also discovered fluctuations in the psychological state of the individuals, which was characterized by an increase in anxiety/depression at the start of the quarantine, followed by a gradual decrease, and a resurgence in anxiety/depression beyond 14 days of quarantine (22). Hawryluck et al. (19) demonstrated a significant rise in post-traumatic stress symptoms in individuals quarantined for more than 10 days during the SARS outbreak as opposed to individuals quarantined <10 days (19). In perspective, the number of days spent in quarantine was much higher among our study participants in comparison to previous studies, with the average duration of quarantine being 28.5 days, most likely attributed to the long incubation period associated with the illness (23). Regardless, the correlation between quarantine duration and impact on mental stress was demonstrated despite this aspect.

Differences in gender distribution were also observed across the groups of varying PSS scores. In general, females were more likely to report being stressed during the quarantine than males. This is in line with previous studies, which have also demonstrated a gender gap in the mental health impact caused by quarantine during outbreaks. Song et al. discovered a similar trend in their study among Chinese individuals in quarantine during the COVID-19 pandemic. In addition, the authors identified that the risk factors for stress were different for males and females. Among males, occupations with unstable income, higher education status, and quarantine duration were the most common risk factors.

In contrast, the need for information about the pandemic, worsening of the outbreak locally, and health problems during the quarantine were the key risk factors among females. Interestingly, the authors noted that males were less adaptive and had a lower tendency to recognize the need for psychological support when compared with females; however, they were more likely to seek medical care in response to infective symptoms (24). The observed gender differences are postulated to be due to the variation in psychological, physiological, and cognitive processes between the two sexes and their consequent response to stressful situations (25–27).

We also observed a relationship between relationship status and PSS scores, with single individuals being at the most significant risk of higher stress. This is in line with the findings from a recent study by Pieh et al. (28) during the COVID19 pandemic, where the authors demonstrated that participants with a good quality relationship scored significantly better on all mental health scales than individuals who were not in a relationship of any kind or those who were in a poor-quality relationship, in that order. The authors concluded that while being in a relationship in itself did not determine mental health status during quarantine, the quality of the relationship certainly played a role (28).

Contrary to expectations, MH-PSS was observed more frequently among individuals with religious beliefs compared to those with no religious beliefs. However, it is essential to note that nearly 80% of our study population identified with a religion, which may have contributed to this unexpected result. Yildirim et al. (29) found that positive religious coping mediated a greater meaning in life, which reduced loneliness during the coronavirus crises in Turkey. In line with this, the Thomas and Barbato (30) published similar findings demonstrating that positive religious coping was inversely related to depressive symptoms and a history of psychological disorders during the COVID-19 pandemic. Interestingly, the authors also found that Muslims had higher levels of positive religious coping than the Christians in their sample population. In our study, we did not assess the extent of religious involvement or the various religious coping tools/ strategies used by participants, which is believed to have played a role in our findings. In our study, we found that a higher educational status was associated with increased stress. The data on the link between educational status and psychological stress during quarantine is obscure. In a study among horse owners during an equine influenza outbreak, Taylor et al. observed that individuals with lower formal educational qualifications were at an increased risk of negative psychological impacts (31). On the other hand, Hawryluck et al. reported that the level of education did not affect both the understanding of quarantine requirements or the psychological impact of quarantining (19). In contrast, Song et al. noted that a higher educational status correlated positively with stress levels during the COVID-19 pandemic (24). Regardless, the need for information about the illness from public health officials and its clarity have been reported to influence the mental health of individuals in quarantine/isolation (32). The educational status of the individual may perhaps play a role in the understanding of this information and, therefore, affect the psychosocial impact of quarantine.

The observed relationship between being a confirmed case of infection, or the index case, in a family and the high levels of perceived stress, has been documented in previous studies. In a study by Jeong et al. during the MERS outbreak, it was reported that individuals who were isolated due to suspicion or confirmation of infection were more likely to manifest anxiety if they experienced symptoms characteristic of the infection and link it to the infection even if the suspected exposure was several months prior to the presentation of these symptoms (33). Studies also show that individuals who have been exposed to the risk of infection tend to worry about spreading the infection to their family members and others who have come into contact with them (32–34).

Recent studies in this area have identified other pre-existing individual characteristics that contribute to stress during pandemics. Osimo et al. (35) investigated the influence of personality traits on stress response during COVID-19 lockdowns and reported that individuals with a lower resilience and emotional stability and higher alexithymia had a poorer emotional response during home containment. Similarly, Moccia et al. (36), through their study on the Italian population during the COVID-19 pandemic, found that individuals with cyclothymic, depressive, and anxious temperaments and those who had a “Need for approval” style as per the Attachment Style Questionnaire (ASQ) were at higher risk of moderate-to-severe psychological distress; whereas ASQ “Confidence” and ASQ “Discomfort with closeness” was found to be protective traits. Another study conducted by Fiorillo et al. (37) during March to May 2020 in Italian population showed individuals with known mental disorders and physical disease had worse levels of depression and anxiety symptoms while individuals with cohabiting people, living with more number of family members and having higher level of satisfaction with one's own life were found to be protective against development of psychiatric symptoms.

Based on our search of the literature, the strength of our study is its multinational population, with participants from a total of 63 countries, making it one of the most diverse of recent publications on the relationship between quarantine during the COVID-19 pandemic and its psychological impact. We identified some of the key risk factors that contribute to anxiety/stress during the period of quarantine/isolation through our analysis. As with any study, there are several limitations to our research. While our survey reached participants of multiple countries, providing a heterogeneous multinational sample, the overall number of responses was relatively low, limiting the size of the study. In addition, we aimed to keep the survey at a length that was palatable to respondents. We were unable to assess several other factors such as pre-existing mental health illnesses, religious coping, individual temperament and self-control, ability to work from home, and living conditions. We believe that our study captures some of the major risk factors for mental stress during quarantine/isolation, specific to the COVID-19 pandemic, and paves the way for further research in this area. The findings of this study should be considered when dealing with psychosocial issues that arise during infectious outbreaks and help identify high-risk groups for negative psychological impact for early intervention.

Taken together our findings, many factors can predict stress in pandemics such as COVID-19, including female sex, being single, higher education status, and being of the non-healthcare profession. These and similar factors should be considered in handling stress and in managing future pandemics.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by ethical approval was obtained from the ethical committee of the IRB of Nagasaki University (Ref. No. 117; Approval number: NU_TMGH_2020_117_1). The patients/participants provided their written informed consent to participate in this study.

All authors give the full consent to publish this study.

We collected data from the individuals who were quarantined/isolated after being suspected or confirmed to have contracted COVID-19. However, they have not involved directly in the setting of the research question or outcome measures. They did not have any role in designing or implementing this work or interpretation of the results.

NH, ND, and LM: design of the idea and study workflow. ND, SM, TG, VT, LL, and PT: data acquisition. ND, SM, LM, AH, TG, LT, AR, FD, VT, and PT: data interpretation. LM, LT, and VT: final analysis. SM, AH, AR, and SD: drafting of the manuscript. NH, ND, LM, and SD: critical revision. All authors contributed to the final approved the final version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.