The COVID-19 pandemic has caused increased community-wide mental health problems, such as depression and anxiety. Studies conducted on the general UK population during the initial pandemic stages have shown a significant increase in depression and anxiety [4]. Research conducted on the general population in Korea during the early stages of the pandemic suggests a high prevalence of depression and anxiety [5,6]. A systematic review and meta-analysis identified depression (26.9%) and anxiety (21.8%) as the prominent mental health outcomes of the COVID-19 pandemic in Chinese populations [7].

SARS-CoV-2 infection has affected the mental health of individuals. Studies indicate that the infection has increased depression and anxiety cases, and the COVID-19 survivors may experience increased depression and anxiety [8]. A study in Korea also showed increased levels of depression and anxiety in hospitalized patients [9].

Debates exist regarding the duration of the mental health effects of SARS-CoV-2 infection. Some studies have reported transient effects of the infection. Matalon et al. [10] reported that depression and anxiety were relieved 1 month after acute SARS-CoV-2 infection among Israeli inpatients. Chevinsky et al. [11] discovered that depression and anxiety remitted within 30 days and 90 days, respectively, among outpatients with SARS-CoV-2 infection in the US. Klaser et al. [12] noted that depression and anxiety were alleviated within 120 days among the US community-sampled individuals who tested positive for SARS-CoV-2. In Korea, Sung et al. [13] performed a retrospective review of health records for patients treated in residential centers for mild SARS-CoV, which reported post-infection increases in depression and anxiety [13].

Meanwhile, other studies suggest a persistent effect of SARS-CoV-2 infection on depression and anxiety. Huang et al. [14] reported that depression and anxiety persisted in 23% of Chinese inpatients at 6 months post-infection. Similarly, Méndez et al. [15] found long-lasting effects of SARS-CoV-2 infection on depression and anxiety among inpatients in Spain. Kim et al. [16] found sustained depression and anxiety 12 months after the infection among inpatients in Korea.

Previous studies have several knowledge gaps in various aspects. First, predominant investigations have been conducted during the prevalence of the Delta variant and associated national lockdowns owing to increased disease severity. Thus, biological and social factors might have affected mental health. Therefore, it is crucial to understand the association between SARS-CoV-2 infection and depression and anxiety when the Omicron variant, with lower severity, is predominant. Second, previous studies have mainly focused on inpatients and outpatients infected with SARS-CoV-2. There are few studies of the association between SARS-CoV-2 infection and depression and anxiety in the community. Therefore, it is essential to observe the effect of SARS-CoV-2 infection on depression and anxiety in the community. Third, most studies are limited to countries with stringent lockdowns, such as China and various European countries. There has been little research conducted on mental health in countries with less severe lockdowns and lower fatality rates, like Korea. Thus, additional research to encompass various countries, including Korea, is essential for generalizing the association between SARS-CoV-2 infection and depression and anxiety.

This study aims to investigate the association between SARS-CoV-2 infection and the severity of psychiatric symptoms, specifically depression and anxiety, during the prevalence of the Omicron variant. Thus, we used data collected from individuals in the Daejeon community in Korea.

Data for this study were obtained from the 2022 Daejeon Mental Health Survey (DMHS), conducted by the Daejeon Regional Mental Health Welfare Center (DRMHWC). DRMHWC is a government-funded institution established by the Ministry of Health and Welfare and the Daejeon Metropolitan Government. The center is situated in Daejeon, a metropolitan city in the central region of Korea with a population of 1.5 million. The center conducts a comprehensive mental health survey of its citizens every 4 years, publishing the results as the DMHS [17].

The DRMHWC conducted an online survey between March 21 and 29, 2022 and employed a structured questionnaire to gather information on physical and mental health as well as demographic information from 1,000 residents of Daejeon aged 19-69. Considering the context of the ongoing COVID-19 pandemic and the prevalence of the Omicron variant, information regarding SARS-CoV-2 infection was also gathered during the DMHS. The DMHS selected proportional stratified sampling options that considered gender, age, and address as stratified variables using resident registration population data provided by the Ministry of the Interior and Safety as of the end of February 2022.

The present study acquired and analyzed the publicly available raw data from the survey released by DRMHWC. Because the data was anonymized and lacked personal identification details of participants, the need for written informed consent was waived. Ethical approval was obtained from the Institutional Review Board of Chungnam National University Hospital (CNUH 2022-08-046).

T-test or chi-square test was conducted to compare the physical health, social activities, and other sociodemographic factors between SARS-CoV-2 infected and noninfected groups. Continuous variables are presented as mean and standard deviation, whereas categorical variables are shown as number and percentage (n, %).

We examined the association between the experience of SARS-CoV-2 infection and the severity of depression (PHQ-9) or anxiety (GAD-7) using the independent t-test.

Furthermore, we conducted a hierarchical regression analysis to assess the effect of the days after Omicron variant infection on the severity of depression and anxiety. Three models were used in this analysis: the days after Omicron variant infection was entered in Model 1. Model 2 adjusted for physical health and social activity status. Model 3 adjusted for all variables stratified by the age groups.

All statistical analyses were performed using SPSS Version 28.0 for Windows (IBM Corp., Armonk, NY, USA) statistical program, and the statistical significance level was set at <0.05.

Table 1 shows the demographic characteristics of SARS-CoV-2 infected and noninfected participants. Among the initial 1,000 participants, 985 were included in the analyses after excluding 15 individuals infected during the Delta variant dominant period. The participants comprised 478 (48.5%) men and 507 (51.5%) women, with an average age of 45.9±13.2 years. Individuals affected by SARS-CoV-2 were significantly younger (43.4 years vs. 46.3 years, p=0.010) and reported higher satisfaction levels with their physical health status (2.8 vs. 3.0, p=0.014) and social activity status (2.8 vs. 3.1, p=0.001) compared with noninfected counterparts.

SARS-CoV-2 infection was not associated with depression and anxiety in the overall population. The mean PHQ-9 scores were 5.1 and 5.3 among the infected and noninfected individuals, respectively (p=0.626). Additionally, the mean GAD-7 scores were 3.9 and 3.9 among the infected and noninfected individuals (p=0.930).

Table 2 shows the results of the association between depression and anxiety and the days after the Omicron variant infection.

For the participants <51 years of age, the severity of depression and anxiety decreased as the days passed after infection (Figure 1). This trend remained consistent even after adjusting for variables. Participants <51 years of age experienced a mild, transient worsening of depression and anxiety. After 40 days, the PHQ-9 and the GAD-7 scores dropped to <10. Thus, no individual scored above the cutoff for mild depression and anxiety after 40 days.

In the ≥51 year age group, although there were no significant differences, Models 2 and 3 showed a significant decrease in depression, along with an insignificant decreasing trend in anxiety.

Although previous studies have shown an association between SARS-CoV-2 infection and depression and anxiety in the community [8], our study did not find a significant association. Moreover, Jung et al. [9] found that among 102 patients with SARS-CoV-2 who were discharged from hospitalization in Korea, depression (48.1%) and anxiety (49.1%) were identified. However, our study of the general population with Omicron infection is inconsistent with previous literature findings. There are several possible explanations for the lack of association. First, considering social factors, it is plausible that individuals actively engaging in positive social support and physical activities might be prone to increased risk of SARS-CoV-2 infection. However, these same activities could exert a protective effect against depression and anxiety by promoting resilience and mitigating the negative effects of SARS-CoV-2 infection [23,24]. Second, the biological factors cannot be dismissed. The Omicron variant was considered dominant in this study. As most Omicron infections are of low severity, the potential influence on depression and anxiety might have been insignificant. Third, the effects of SARS-CoV-2 infection could be short-lived, leading to only minor effects on community-wide depression and anxiety levels. The study suggests that individuals experienced temporary bouts of depression and anxiety post-SARS-CoV-2 infection. Consequently, detecting subtle variations would necessitate larger sample sizes.

It is unclear how mental sequelae caused by SARS-CoV-2 infection persist. In a study focusing on hospitalized patients with SARS-CoV-2 infection in Israel, Matalon et al. [10] found that depression and anxiety decreased within a month. Studies in outpatient and community populations in the United States have also found reductions in depression and anxiety within three months [11]. In contrast, studies conducted on hospitalized patients in China, Spain, and South Korea reported that depression and anxiety persisted for >6 months [14-16]. Our results support the findings of the aforementioned studies, which reported a short-lived effect of SARS-CoV infection on depression and anxiety.

Primarily, social factors need to be considered. Most of the studies showing long-lasting effects of SARS-CoV-2 infection have been conducted in countries with stringent lockdown regulations and high fatality rates. In contrast, this study was conducted during a period of comparatively relaxed lockdowns, reduced social media influence, and low fatality rates [25]. Therefore, these social factors could have contributed to decreased psychological stress and subsequent decreases in depression and anxiety levels [26].

Furthermore, the biological factors should also be considered. Coronaviruses can cause psychopathological effects through two pathways: direct viral infection of the central nervous system or indirect effects via immune response [27]. Considering the relatively mild nature of the Omicron variant [28], there may have been a smaller biological inflammatory response, leading to a potentially reduced effect on depression and anxiety levels. This is consistent with a previous study conducted on SARS-CoV-2 infected inpatients, where patients with Omicron variant infection exhibited decreased depression and anxiety symptoms [29]. This suggests a relatively low risk of experiencing depression and anxiety due to Omicron variant infection in community samples.

We found an association between Omicron variant infection and elevated depression and anxiety symptoms among younger adults, particularly within the first month post-infection. Multiple factors contribute to these distinctions. First, social factors could play a pivotal role, considering the links between depressive and anxiety symptoms and feelings of loneliness, as well as lower resilience to stress among younger adults. Therefore, younger adults might have been particularly susceptible to symptom exacerbation during periods of lockdowns and related disruptions. Similar trends were noted in previous studies involving younger adults during the COVID-19 pandemic, highlighting the interplay between feelings of loneliness, low resilience, and increased depression and anxiety [30].

Second, biological factors should also be considered. A few studies reported elevated anxiety levels among young COVID-19 survivors, although studies on age-related biological factors remains limited [31]. Additionally, the relatively smaller cohort of older adults might have limited our ability to discern changes in depression and anxiety as older adults in this study had little effect. Therefore, future studies with larger older adult participation are warranted to elucidate this aspect.

The major strength of our study lies in the use of community sample data through proportional stratified sampling. This approach reduced the sampling bias often present in many previous studies that focused on hospitalized or outpatient populations. Additionally, by minimizing the influence of socioeconomic factors, we were able to obtain results that are more generalizable.

In the current context of ongoing sporadic SARS-CoV-2 infections continuing post-pandemic, our research provides clinical and policy implications. First, our study showed a transient intensification of depression and anxiety symptoms following a mild SARS-CoV-2 infection. This implies the need for timely screening and intervention for mental health issues immediately after infection. Second, it is necessary to establish targeted intervention strategies for young adults who are actively engaged in social activities. Enhancing the accessibility of mental health services, such as online digital mental health resources, is also needed.

However, limitations exist. The cross-sectional design hinders the establishment of causal relationships between the study variables. Potential sampling bias could arise from the online survey approach, possibly limiting generalizability to less technologically savvy or lower-income populations. It is possible that individuals with more severe symptoms were not included in the study. However, during the online survey, SARS-CoV-2 severity was generally low in Korea, which may reduce the potential for significant bias. All variables in the study were self-reported, which may limit the accuracy of variables such as diagnosis or the presence of SARS-CoV-2 infection. Therefore, further studies are necessary to address the limitations and improve the quality of our findings.

In conclusion, this study indicates that depression and anxiety symptoms may temporarily worsen in younger adults following Omicron variant infection, implying a short-lived effect on this population. Further longitudinal studies are essential to investigate the factors contributing to mental health outcomes after SARS-CoV-2 infection.