Mortality Rates According to the Time of Onset of Mental Disorders Among Patients With Coronavirus Disease 2019 in South Korea: A Nationwide Retrospective Study

Jungeun Kim; Subin Park

doi:10.30773/pi.2026.0054

Psychiatry Investig > Volume 23(7); 2026 > Article

Kim and Park: Mortality Rates According to the Time of Onset of Mental Disorders Among Patients With Coronavirus Disease 2019 in South Korea: A Nationwide Retrospective Study

Original Article

Psychiatry Investigation 2026;23(7):937-944.

Published online: July 9, 2026

DOI: https://doi.org/10.30773/pi.2026.0054

Mortality Rates According to the Time of Onset of Mental Disorders Among Patients With Coronavirus Disease 2019 in South Korea: A Nationwide Retrospective Study

Jungeun Kim¹

, Subin Park²

¹Department of Research Planning, National Center for Mental Health, Seoul, Republic of Korea

²Mental Health Research Institute, National Center for Mental Health, Seoul, Republic of Korea

Correspondence: Subin Park, MD, PhD, Mental Health Research Institute, National Center for Mental Health, 127 Yongmasan-ro, Gwangjin-gu, Seoul 04933, Republic of Korea Tel: +82-2-2204-0103, Fax: +82-2-2204-0362, E-mail: subin-21@hanmail.net

Received February 18, 2026 Revised April 26, 2026 Accepted April 27, 2026

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective

This study aimed to investigate the association between the timing of mental disorder diagnosis and all-cause mortality among patients with coronavirus disease 2019 (COVID-19) during the initial period of the pandemic.

Methods

This retrospective study used the K-COV-N cohort (Korea Disease Control and Prevention Agency-COVID-19-National Health Insurance Service cohort). Patients with confirmed COVID-19 between October 2020 and December 2021 were classified into three groups: those without mental disorders, those with pre-existing mental disorders, and those with newly diagnosed mental disorders during the COVID-19 pandemic. Logistic regression analysis was performed to estimate the association between mental disorder group and all-cause mortality.

Results

A total of 432,852 patients with COVID-19 were included in the analysis. Of these, 351,519 (81.21%) had no mental disorders, 54,846 (12.67%) had pre-existing mental disorders, and 26,487 (6.12%) had newly diagnosed mental disorders during the pandemic. The overall all-cause mortality rate was 0.72% (n=3,099). Compared with patients without mental disorders, those with pre-existing mental disorders (adjusted odds ratio [aOR], 1.33; 95% confidence interval [CI], 1.21-1.47) and those with newly diagnosed mental disorders (aOR, 1.63; 95% CI, 1.44-1.84) had higher odds of all-cause mortality.

Conclusion

Among patients with COVID-19, both pre-existing and newly diagnosed mental disorders were associated with increased all-cause mortality, with a stronger association observed for newly diagnosed mental disorders.

Keywords: Mental disorders, Mortality, COVID-19, South Korea

INTRODUCTION

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 [1]. Since December 2019, the number of COVID-19 cases worldwide has reached 778 million, with over 7.1 million deaths [1]. In South Korea, 34 million confirmed cases and 35,605 deaths were reported as of August 2023, indicating a mortality rate of approximately 0.1% [2]. Contrary to the current situation, in the initial phase of the pandemic, many countries implemented extensive containment measures, including nationwide lockdowns, prolonged social distancing mandates, and restrictions on mobility [3]. Although necessary for infection control, these measures contributed to heightened psychosocial stress, uncertainty, and isolation, intensifying mental health symptoms across populations [4]. Numerous studies have demonstrated that the pandemic environment increased the risk of developing or exacerbating psychiatric conditions, including posttraumatic stress disorder, depression, and anxiety [5-7].

Prior outbreaks of infectious diseases have similarly revealed the psychiatric vulnerabilities associated with large-scale public health crises [8]. Research conducted during previous epidemics such as Ebola, severe acute respiratory syndrome, and Middle East respiratory syndrome indicated that 0.9% to 4% of infected individuals experienced psychotic symptoms or episodes, underscoring the mental health risks inherent in infectious disease contexts [9].

Furthermore, studies on COVID-19 have consistently re-vealed that compared to individuals without mental illnesses, those with mental illnesses experience worse outcomes [10-12]. Patients with mental illnesses are at increased risk of medical conditions due to unhealthy lifestyle habits (e.g., smoking and alcohol consumption) and a low socioeconomic status [13-15]. Stigma and discrimination towards mental illness and the poor communication skills of those with mental disorders may hamper proper and timely provision of medical interventions for COVID-19 [16]. Several patients with mental disorders (including high anxiety) express hesitancy toward receiving the COVID-19 vaccine, and such unvaccinated individuals experience a worse prognosis after contracting COVID-19 [17]. Furthermore, psychiatric drugs taken by patients with mental illnesses lower the efficiency of COVID-19 treatments [18].

The factors contributing to COVID-19-related mortality may differ between those with long-standing mental disorders and those newly diagnosed with mental disorders in a stressful environment such as during the COVID-19 pandemic. For example, patients suffering from chronic mental disorders may present with more chronic or co-existing physical diseases that have been left untreated [19]; however, patients with newly developed mental disorders may not do so and may experience a high mortality rate due to other problems.

Therefore, in the current study, we investigated the mortality rate among patients with mental disorders during the COVID-19 pandemic according to the time of mental illness onset. Patients with mental disorders were divided into those with pre-existing mental disorders and those newly diagnosed with mental disorders during the pandemic; their mortality rates were compared with the mortality rate of those without any mental disorders. In addition, factors affecting the mortality rate among patients with COVID-19 were identified.

METHODS

Data source and study population

South Korea operates the National Health Insurance Service (NHIS), which is a comprehensive national health insurance system that covers 98% of the nation’s population [20]. This study was performed using the K-COV-N cohort (Korea Disease Control and Prevention Agency-COVID-19-National Health Insurance Service cohort), a linked database combining NHIS claims data with data from the Korea Disease Control and Prevention Agency (KDCA) for policy and academic research. Specifically, the NHIS data contain demographic information and healthcare utilization records, including diagnoses (using the International Classification of Diseases, 10th revision [ICD-10]), procedures, and healthcare visits [20]. Moreover, the KDCA supplies data on individuals confirmed to have COVID-19 at public health and medical centers; these data include COVID-19 confirmation dates, infection routes, and vaccination types. Data on patients with confirmed COVID-19 were available from October 2020 to December 2021, and data on their diagnosis and medical records could be reviewed from 2017. Additionally, the death records of patients with confirmed COVID-19 were available until March 2022.

We included all individuals in South Korea aged 18-79 years with confirmed COVID-19 between October 10, 2020, and December 31, 2021. Patients with organic mental disorders (ICD-10 codes F00-F09), including dementia, and those aged >80 years were excluded (Figure 1). Organic mental disorders were excluded because they represent a clinically distinct category with substantially different age distribution, comorbidity burden, cognitive impairment, and prognostic profile compared with other psychiatric disorders [21,22].

Measures

The patients were categorized into the following 3 groups: 1) those without mental disorders, 2) those with pre-existing mental disorders, and 3) those initially diagnosed with mental disorders during the COVID-19 pandemic. For subgroup analyses, psychiatric disorders were additionally classified according to major ICD-10 diagnostic categories (F1-F9). Because some individuals had more than one psychiatric diagnosis, these diagnostic categories were treated as non-mutually exclusive, and a given patient could be included in more than one subgroup. Patients were deemed to have mental disorders if they had at least two outpatient visits or at least one hospitalization with a mental and behavioral disorder diagnosis (ICD-10 codes F1-F9) [23]. Pre-existing mental disorders were defined as those diagnosed before February 2020; newly diagnosed mental disorders were defined as those diagnosed for the first time during the COVID-19 pandemic (from February 2020 onward). No additional temporal restriction was applied between the date of COVID-19 diagnosis and the date of psychiatric diagnosis.

Demographic variables included sex (male or female), age categories (18-49, 50-59, 60-69, and 70-79 years), place of COVID-19 occurrence (hospitals and nursing homes, among others), and insurance type (National Health Insurance or Medical Aid). Completion of COVID-19 vaccination was defined as an individual receiving a second or higher vaccine dose or the first dose of the Janssen COVID-19 vaccine [24]. Booster doses and time since vaccination were not considered in the present analysis.

Severe events during the pandemic included admissions to the intensive care unit (ICU), the use of mechanical ventilation, and the development of acute respiratory distress syndrome [16]. The Charlson Comorbidity Index (CCI) was calculated [25]; it is used to determine the number and severity of comorbid physical diseases in an individual. The CCI scores were classified as 0, 1-2, and ≥3. A score of 0 indicates the absence of a comorbidity; conversely, higher CCI scores indicate the presence of multiple comorbid or severe diseases. The main outcome measure was all-cause mortality.

Statistical analysis

The baseline characteristics of all included patients are presented as percentages (for categorical variables). Differences among the three groups were assessed using the chi-square test. Multiple logistic regression models were used to estimate the odds ratios (ORs) and adjusted ORs (aORs) for all-cause mortality according to the timing of mental disorder diagnosis. Fully adjusted models were constructed using sex, age group, CCI, COVID-19 vaccination status, insurance type, and place of COVID-19 occurrence as covariates. In supplementary analyses, we further examined mortality according to ICD-10 psychiatric diagnostic categories (F1-F9) using the same logistic regression framework. Because psychiatric diagnoses were not mutually exclusive, patients could contribute to more than one diagnostic subgroup. All the statistical analyses were performed via SAS (version 9.4; SAS Institute Inc.) and RStudio (R version 4.3.3).

Ethics approval and consent to participate

This study protocol was reviewed and approved by the Institutional Review Board of the National Center for Mental Health (IRB No. 116271-2021-23) and the NHIS (NHIS-2022-1-506). Informed consent was waived because the data analyses were performed retrospectively using anonymized data from the South Korean NHIS database.

RESULTS

A total of 432,852 patients with confirmed COVID-19 were included in this study. These included 351,519 (81.21%) patients without mental disorders, 54,846 (12.67%) patients with pre-existing mental disorders, and 26,487 (6.12%) patients with newly diagnosed mental disorders (Figure 1). Among all patients with confirmed cases of COVID-19, the proportion of men was greater than that of women in the group without mental disorders at 54.12%. On the other hand, the proportion of women was high in the mental disorders group. Regarding age distribution, patients without mental disorders comprised a high proportion of patients aged 18-49 years, and patients with pre-existing mental disorders comprised the highest proportion of those aged >70 years. The COVID-19 vaccination rate was the lowest among those with newly diagnosed mental disorders. Hospitals or nursing home related COVID-19 infections accounted for 5.77% of pre-existing mental disorders, followed by those with newly diagnosed mental disorders and those with no mental disorders. The 3+ CCI rate was the highest in patients with pre-existing mental disorders; in patients with newly diagnosed mental disorders, the severe event rate was the highest at 3.66% (Table 1).

The overall mortality rate was 0.72% (patients with newly diagnosed mental disorders: 1.53%, patients with pre-existing mental disorders: 1.49%, and patients without mental disorders: 0.53%). The mortality rates were higher in men than in women; furthermore, mortality increased with older age, in unvaccinated patients, with in-hospital or nursing home occurrences, with Medical Aid as the insurance type, and with higher CCI scores.

Logistic regression analysis was performed to estimate the crude ORs and aORs for all-cause mortality across the three groups. Compared with patients without mental disorders, the crude ORs for all-cause mortality were 2.81 in patients with pre-existing mental disorders and 2.90 in those with newly diagnosed mental disorders; however, the crude ORs did not differ significantly between the two groups. The aORs were 1.33 and 1.63, respectively, and were significantly higher in the newly diagnosed mental disorder group than in the pre-existing mental disorder group (Table 2). To assess the heterogeneity of psychiatric disorders, additional subgroup analyses by ICD-10 diagnostic category were performed and are presented in Supplementary Table 1. The associations between psychiatric disorders and all-cause mortality varied across diagnostic categories.

DISCUSSION

The principal finding of this study is that all-cause mortality among patients with COVID-19 was significantly higher in those with mental disorders than in those without mental disorders, with the highest all-cause mortality observed among those newly diagnosed during the pandemic. This finding suggests that not only the presence of mental disorders but also the timing of mental disorder diagnosis may be relevant to mortality risk among patients with COVID-19.

These findings are consistent with those of previous studies. A domestic study reported that patients with mental illness had approximately a two-fold higher risk of COVID-19- related mortality compared with those without mental illness [16]. Similarly, large international cohort studies have demonstrated a significantly higher risk of COVID-19-related mortality among individuals with mental disorders compared with the general population, with particularly pronounced increases observed in patients with mood disorders and schizophrenia [24]. In line with these previous reports, our subgroup analyses by diagnostic category also showed significantly increased mortality during the COVID-19 pandemic among patients with mood disorders, schizophrenia, schizotypal and delusional disorders, and mental and behavioral disorders due to psychoactive substance use. However, most prior studies focused on the presence of mental disorders alone, and few examined differences in mortality according to the timing of mental illness onset. In this regard, our study extends previous research by highlighting the prognostic importance of mental illness onset during the pandemic.

Age was the strongest determinant of all-cause mortality in our study and showed the largest effect size in multivariable analyses. Consistent with this, the proportion of older adults was highest among patients with pre-existing mental disorders (11.52%), followed by those newly diagnosed with mental disorders during the pandemic (9.10%) and those without mental disorders (4.88%). Older age is well known to be associated with increased mortality from COVID-19, partly due to a higher burden of chronic medical conditions and agerelated declines in immune function [26-28].

Despite this age distribution, mortality was highest among patients newly diagnosed with mental disorders during the pandemic, rather than among those with pre-existing mental disorders, despite the higher proportion of older adults in that group. This finding suggests that factors other than age may have contributed to the excess mortality observed in the newly diagnosed group. Patients newly diagnosed with mental disorders had a higher proportion of men and the highest rate of severe clinical events, suggesting greater clinical vulnerability at the time of COVID-19 infection. These characteristics may have contributed to the elevated mortality risk beyond the effect of age alone.

Several mechanisms may explain the increased mortality observed among patients with mental disorders. First, established risk factors for severe COVID-19, such as smoking, diabetes, and cardiovascular disease, are more prevalent among individuals with mental illnesses than in the general population [29]. Second, immune dysregulation associated with mental disorders may impair host responses to infection and contribute to worse clinical outcomes [30]. Third, patients with mental disorders have been reported to have lower COVID-19 vaccination rates than the general population, which may increase the risk of severe disease and death [17].

COVID-19 vaccination is a critical protective factor against severe disease and mortality [31]. Large observational studies have consistently shown substantially higher risks of hospitalization and death among unvaccinated individuals compared with vaccinated individuals [32]. In our study, vaccination status was the second most influential predictor of mortality after age. In South Korea, patients with pre-existing mental disorders were likely prioritized for vaccination because they were classified as residents or workers in nursing hospitals or psychiatric facilities [33]. In contrast, patients with mental disorders newly identified during the pandemic may not have been covered by policy-based vaccination priorities and may also have been more hesitant to receive vaccination due to elevated levels of depression or anxiety [17].

In addition, severe COVID-19 illness in the absence of vaccination may have contributed to the subsequent development of newly diagnosed mental disorders. Previous studies have shown that the incidence of psychiatric disorders increases with greater COVID-19 severity, particularly among hospitalized patients and those admitted to ICUs [34]. This bidirectional relationship between COVID-19 severity and mental illness may have further exacerbated mortality risk among newly diagnosed patients [35].

In this study, approximately 19% of patients with COVID-19 experienced mental disorders during the pandemic, and nearly one-third of these cases were newly diagnosed. This finding indicates a substantial increase in newly identified mental health problems during this period and is consistent with reports from other countries [34-36]. Extreme social isolation, stigma, psychological distress following a sudden COVID-19 diagnosis, disruption of social relationships, unemployment, and income reduction during the pandemic may have contributed to the rapid deterioration of mental health [37,38]. These factors may not only increase the risk of developing mental disorders but also adversely affect COVID-19 outcomes through delayed healthcare utilization, reduced treatment adherence, and deterioration in health-related behaviors [39]. In particular, patients newly diagnosed with mental disorders during the pandemic may have experienced COVID-19 infection in the absence of well-established psychological and social support systems, which may partially explain the higher mortality observed in this group [4,34].

This study has several limitations. First, an important limitation of this study is the temporal ambiguity in the newly diagnosed mental disorder group. Because newly diagnosed mental disorders were identified based on psychiatric diagnoses first recorded during the pandemic period, and no temporal restriction was applied between COVID-19 diagnosis and psychiatric diagnosis, some psychiatric diagnoses may have occurred after COVID-19 infection or during hospitalization for severe illness. In such cases, these diagnoses may reflect acute psychiatric symptoms related to severe infection, psychological distress following hospitalization, or psychiatric complications of COVID-19. Therefore, the observed association between newly diagnosed mental disorders and increased mortality should be interpreted with caution, as it may partly reflect reverse causality. Second, patients with organic mental disorders (ICD-10 codes F00-F09), including dementia, were excluded from the analysis, although this category is included within the classification of mental disorders. Therefore, the findings of this study may not be generalizable to patients with organic mental disorders and should be interpreted primarily in relation to psychiatric disorders other than organic mental disorders. Third, the analyzed data represented only individuals with confirmed COVID-19 between October 2020 and December 2021. Therefore, the findings of this study are primarily applicable to the early phases of the COVID-19 pandemic. Furthermore, because the observation period from COVID-19 diagnosis to death was relatively short, the longterm effects of COVID-19 on mortality could not be evaluated. Further studies using longer follow-up periods are warranted.

In conclusion, this nationwide retrospective study showed that both pre-existing and newly diagnosed mental disorders were associated with increased all-cause mortality among patients with COVID-19, with a stronger association observed in those newly diagnosed during the pandemic. These findings indicate that mental health status, particularly the timing of mental disorder diagnosis, may be relevant to mortality risk in patients with COVID-19 and highlight the need for closer clinical attention to mental health during infectious disease outbreaks, particularly among patients with newly identified mental disorders.

Supplementary Materials

The Supplement is available with this article at https://doi.org/10.30773/pi.2026.0054.

Supplementary Table 1.

Crude and adjusted ORs for all-cause mortality according to ICD-10 psychiatric diagnostic categories and the timing of mental disorder diagnosis among patients with COVID-19

pi-2026-0054-Supplementary-Table-1.pdf

Notes

Availability of Data and Material

The data that support the findings of this study are available from National Health Insurance System; however, restrictions apply to the availability of these data, which were used under licence for the current study and are therefore not publicly available. Data are, however, available from the authors upon reasonable request and with permission from the National Health Insurance System (https://nhiss.nhis.or.kr).

Conflicts of Interest

Subin Park, a contributing editor of the Psychiatry Investigation, was not involved in the editorial evaluation or decision to publish this article. All remaining authors have declared no conflicts of interest.

Author Contributions

Conceptualization: Subin Park, Jungeun Kim. Data curation: Jungeun Kim. Formal analysis: Jungeun Kim. Funding acquisition: Subin Park. Investigation: Jungeun Kim. Methodology: Subin Park, Jungeun Kim. Project administration: Jungeun Kim. Resources: Subin Park. Software: Jungeun Kim. Supervision: Subin Park. Validation: Subin Park. Visualization: Jungeun Kim. Writing—original draft: Jungeun Kim. Writing—review & editing: Subin Park, Jungeun Kim.

Funding Statement

This research was supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (grant number: RS-2022-KH128210). This study was conducted using the database of the Korea Disease Control and Prevention Agency (KDCA) and the National Health Insurance Service (NHIS) for policy and academic research (KDCA-NHIS-2022-1-506).

Acknowledgments

None

Figure 1.

Flowchart of the study population. COVID-19, coronavirus disease 2019.

Table 1.

Baseline characteristics of patients with COVID-19 according to mental disorder status

Characteristics	Total	No mental disorders	Pre-existing mental disorders	Newly diagnosed mental disorders	p
Total	432,852 (100)	351,519 (81.21)	54,846 (12.67)	26,487 (6.12)
Sex					<0.001^***
Male	225,048 (51.99)	190,243 (54.12)	23,050 (42.03)	11,755 (44.38)
Female	207,804 (48.01)	161,276 (45.88)	31,796 (57.97)	14,732 (55.62)
Age group (years)					<0.001^***
18-49	249,190 (57.57)	214,025 (60.89)	21,985 (40.08)	13,180 (49.76)
50-59	81,299 (18.78)	64,613 (18.38)	11,643 (21.23)	5,043 (19.04)
60-69	76,471 (17.67)	55,718 (15.85)	14,899 (27.17)	5,854 (22.10)
70-79	25,892 (5.98)	17,163 (4.88)	6,319 (11.52)	2,410 (9.10)
COVID-19 vaccination status					<0.001^***
Yes	368,870 (85.22)	299,556 (85.22)	47,001 (85.70)	22,313 (84.24)
No	63,982 (14.78)	51,963 (14.78)	7,845 (14.30)	4,174 (15.76)
Place of COVID-19 occurrence					<0.001^***
Hospital or nursing home	12,152 (2.81)	7,967 (2.27)	3,162 (5.77)	1,023 (3.86)
Others	420,700 (97.19)	343,552 (97.73)	51,684 (94.23)	25,464 (96.14)
Insurance type					<0.001^***
National Health Insurance	421,811 (97.45)	345,972 (98.42)	50,524 (92.12)	25,315 (95.58)
Medical Aid	11,041 (2.55)	5,547 (1.58)	4,322 (7.88)	1,172 (4.42)
CCI					<0.001^***
0	126,897 (29.32)	115,808 (32.95)	6,578 (11.99)	4,511 (17.03)
1-2	212,611 (49.12)	174,696 (49.70)	24,743 (45.11)	13,172 (49.73)
≥3	93,344 (21.56)	61,015 (17.36)	23,525 (42.89)	8,804 (33.24)
Severe events	6,843 (1.58)	4,313 (1.23)	1,561 (2.85)	969 (3.66)	<0.001^***
Outcome
Mortality	3,099 (0.72)	1,878 (0.53)	815 (1.49)	406 (1.53)	<0.001^***

Data are presented as number (%). Pre-existing mental disorders were diagnosed before the pandemic; newly diagnosed mental disorders were first diagnosed during the pandemic.

^*** p<0.001 by chi-square test.

CCI, Charlson Comorbidity Index; COVID-19, coronavirus disease 2019.

Table 2.

Crude and adjusted ORs for all-cause mortality according to the timing of mental disorder diagnosis among patients with COVID-19

Variables	Total, N	Deaths, N (%)	Crude OR (95% CI)	Adjusted OR (95% CI)
Total	432,852	3,099 (0.72)
Group
No mental disorders	351,519	1,878 (0.53)	1	1
Pre-existing mental disorders	54,846	815 (1.49)	2.81 (2.59, 3.05)	1.33 (1.21, 1.47)
Newly diagnosed mental disorders	26,487	406 (1.53)	2.90 (2.60, 3.23)	1.63 (1.44, 1.84)
Sex
Male	225,048	2,102 (0.93)	1.96 (1.81, 2.11)	2.51 (2.31, 2.73)
Female	207,804	997 (0.48)	1	1
Age group (years)
18-49	249,190	220 (0.09)	1	1
50-59	81,299	434 (0.53)	6.07 (5.16, 7.15)	6.32 (5.35, 7.46)
60-69	76,471	1,108 (1.45)	16.64 (14.39, 19.23)	16.18 (13.90, 18.84)
70-79	25,892	1,337 (5.16)	61.62 (53.40, 71.11)	54.17 (46.40, 63.25)
COVID-19 vaccination status
Yes	368,870	975 (0.26)	1	1
No	63,982	2,124 (3.32)	12.96 (12.01, 13.98)	24.23 (22.30, 26.32)
Place of COVID-19 occurrence
Hospital or nursing home	12,152	502 (4.13)	6.94 (6.29, 7.65)	3.59 (3.19, 4.05)
Others	420,700	2,597 (0.62)	1	1
Insurance type
National Health Insurance	421,811	2,691 (0.64)	1	1
Medical Aid	11,041	408 (3.70)	5.98 (5.38, 6.64)	1.63 (1.44, 1.85)
CCI
0	126,897	242 (0.19)	1	1
1-2	212,611	729 (0.34)	1.80 (1.56, 2.08)	1.50 (1.29, 1.74)
≥3	93,344	2,128 (2.28)	12.21 (10.69, 13.95)	4.15 (3.59, 4.79)

Pre-existing mental disorders were diagnosed before the pandemic; newly diagnosed mental disorders were first diagnosed during the pandemic. Adjusted ORs were calculated after controlling for sex, age group, COVID-19 vaccination status, place of COVID-19 occurrence, insurance type, and CCI. CCI, Charlson Comorbidity Index; CI, confidence interval; COVID-19, coronavirus disease 2019; OR, odds ratio.

REFERENCES

1. World Health Organization. Coronavirus disease (COVID-19) pandemic [Internet] Available at: https://www.who.int/emergencies/diseases/novel-coronavirus-2019. Accessed January 19, 2026.

2. Korea Disease Control and Prevention Agency. COVID-19 domestic outbreak status [Internet] Available at: https://dportal.kdca.go.kr/pot/cv/trend/dmstc/selectMntrgSttus.do. Accessed January 19, 2026.

3. Ganesan B, Al-Jumaily A, Fong KNK, Prasad P, Meena SK, Tong RK. Impact of coronavirus disease 2019 (COVID-19) outbreak quarantine, isolation, and lockdown policies on mental health and suicide. Front Psychiatry 2021;12:565190

4. Brooks SK, Webster RK, Smith LE, Woodland L, Wessely S, Greenberg N, et al. The psychological impact of quarantine and how to reduce it: rapid review of the evidence. Lancet 2020;395:912-920.

5. Vindegaard N, Benros ME. COVID-19 pandemic and mental health consequences: systematic review of the current evidence. Brain Behav Immun 2020;89:531-542.

6. Pfefferbaum B, North CS. Mental health and the Covid-19 pandemic. N Engl J Med 2020;383:510-512.

7. Ko M, Cho HM, Park J, Chi S, Han C, Yi HS, et al. Impact of the coronavirus disease pandemic on mental health among local residents in Korea: a cross sectional study. J Korean Med Sci 2021;36:e322.

8. Leung CMC, Ho MK, Bharwani AA, Cogo-Moreira H, Wang Y, Chow MSC, et al. Mental disorders following COVID-19 and other epidemics: a systematic review and meta-analysis. Transl Psychiatry 2022;12:205

9. Brown E, Gray R, Lo Monaco S, O’Donoghue B, Nelson B, Thompson A, et al. The potential impact of COVID-19 on psychosis: a rapid review of contemporary epidemic and pandemic research. Schizophr Res 2020;222:79-87.

10. Toubasi AA, AbuAnzeh RB, Tawileh HBA, Aldebei RH, Alryalat SAS. A meta-analysis: the mortality and severity of COVID-19 among patients with mental disorders. Psychiatry Res 2021;299:113856

11. Vai B, Mazza MG, Delli Colli C, Foiselle M, Allen B, Benedetti F, et al. Mental disorders and risk of COVID-19-related mortality, hospitalisation, and intensive care unit admission: a systematic review and metaanalysis. Lancet Psychiatry 2021;8:797-812.

12. Molero P, Reina G, Blom JD, Martínez-González MÁ, Reinken A, de Kloet ER, et al. COVID-19 risk, course and outcome in people with mental disorders: a systematic review and meta-analyses. Epidemiol Psychiatr Sci 2023;32:e61.

13. Bellos S, Skapinakis P, Rai D, Zitko P, Araya R, Lewis G, et al. Crosscultural patterns of the association between varying levels of alcohol consumption and the common mental disorders of depression and anxiety: secondary analysis of the WHO collaborative study on psychological problems in general health care. Drug Alcohol Depend 2013;133:825-831.

14. Cook BL, Wayne GF, Kafali EN, Liu Z, Shu C, Flores M. Trends in smoking among adults with mental illness and association between mental health treatment and smoking cessation. JAMA 2014;311:172-182.

15. McLaughlin KA, Costello EJ, Leblanc W, Sampson NA, Kessler RC. Socioeconomic status and adolescent mental disorders. Am J Public Health 2012;102:1742-1750.

16. Jeon HL, Kwon JS, Park SH, Shin JY. Association of mental disorders with SARS-CoV-2 infection and severe health outcomes: nationwide cohort study. Br J Psychiatry 2021;218:344-351.

17. Payberah E, Payberah D, Sarangi A, Gude J. COVID-19 vaccine hesitancy in patients with mental illness: strategies to overcome barriers-a review. J Egypt Public Health Assoc 2022;97:5

18. Ostuzzi G, Papola D, Gastaldon C, Schoretsanitis G, Bertolini F, Amaddeo F, et al. Safety of psychotropic medications in people with COVID-19: evidence review and practical recommendations. BMC Med 2020;18:215

19. Carswell C, Brown JVE, Lister J, Ajjan RA, Alderson SL, Balogun-Katung A, et al. The lived experience of severe mental illness and longterm conditions: a qualitative exploration of service user, carer, and healthcare professional perspectives on self-managing co-existing mental and physical conditions. BMC Psychiatry 2022;22:479

20. Seong SC, Kim YY, Khang YH, Park JH, Kang HJ, Lee H, et al. Data resource profile: the national health information database of the National Health Insurance Service in South Korea. Int J Epidemiol 2017;46:799-800.

21. Mok VCT, Pendlebury S, Wong A, Alladi S, Au L, Bath PM, et al. Tackling challenges in care of Alzheimer’s disease and other dementias amid the COVID-19 pandemic, now and in the future. Alzheimers Dement 2020;16:1571-1581.

22. Chen WY, Huang SJ, Chang CK, Pan CH, Su SS, Yang TW, et al. Excess mortality and risk factors for mortality among patients with severe mental disorders receiving home care case management. Nord J Psychiatry 2021;75:109-117.

23. Park SJ, Rim SJ, Jo M, Lee MG, Kim G, Park S. Self-injurious behavior rate in the short-term period of the COVID-19 pandemic in Korea. J Korean Med Sci 2022;37:e45.

24. Lee DW, Bae YS, Lee JR, Sohn JH, Lee H, Lee JY. COVID-19 vaccination, incidence, and mortality rates among individuals with mental disorders in South Korea: a nationwide retrospective study. Asian J Psychiatr 2023;85:103600

25. Charlson ME, Pompei P, Ales KL, MacKenzie CR. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis 1987;40:373-383.

26. Dessie ZG, Zewotir T. Mortality-related risk factors of COVID-19: a systematic review and meta-analysis of 42 studies and 423,117 patients. BMC Infect Dis 2021;21:855

27. Wang K, Zuo P, Liu Y, Zhang M, Zhao X, Xie S, et al. Clinical and laboratory predictors of in-hospital mortality in patients with coronavirus disease-2019: a cohort study in Wuhan, China. Clin Infect Dis 2020;71:2079-2088.

28. Shaw AC, Joshi S, Greenwood H, Panda A, Lord JM. Aging of the innate immune system. Curr Opin Immunol 2010;22:507-513.

29. De Hert M, Correll CU, Bobes J, Cetkovich-Bakmas M, Cohen D, Asai I, et al. Physical illness in patients with severe mental disorders. I. Prevalence, impact of medications and disparities in health care. World Psychiatry 2011;10:52-77.

30. Miller AH, Raison CL. The role of inflammation in depression: from evolutionary imperative to modern treatment target. Nat Rev Immu nol 2016;16:22-34.

31. de Gier B, van Asten L, Boere TM, van Roon A, van Roekel C, Pijpers J, et al. Effect of COVID-19 vaccination on mortality by COVID-19 and on mortality by other causes, the Netherlands, January 2021-January 2022. Vaccine 2023;41:4488-4496.

32. Mohammed I, Nauman A, Paul P, Ganesan S, Chen KH, Jalil SMS, et al. The efficacy and effectiveness of the COVID-19 vaccines in reducing infection, severity, hospitalization, and mortality: a systematic review. Hum Vaccin Immunother 2022;18:2027160

33. Jung J. Preparing for the coronavirus disease (COVID-19) vaccination: evidence, plans, and implications. J Korean Med Sci 2021;36:e59.

34. Taquet M, Geddes JR, Husain M, Luciano S, Harrison PJ. 6-month neurological and psychiatric outcomes in 236 379 survivors of COVID-19: a retrospective cohort study using electronic health records. Lancet Psychiatry 2021;8:416-427.

35. Taquet M, Luciano S, Geddes JR, Harrison PJ. Bidirectional associations between COVID-19 and psychiatric disorder: retrospective cohort studies of 62 354 COVID-19 cases in the USA. Lancet Psychiatry 2021;8:130-140.

36. Park HY, Song IA, Lee SH, Sim MY, Oh HS, Song KH, et al. Prevalence of mental illness among COVID-19 survivors in South Korea: nationwide cohort. BJPsych Open 2021;7:e183

37. Chen D, Song F, Tang L, Zhang H, Shao J, Qiu R, et al. Quarantine experience of close contacts of COVID-19 patients in China: a qualitative descriptive study. Gen Hosp Psychiatry 2020;66:81-88.

38. Pietrabissa G, Simpson SG. Psychological consequences of social isolation during COVID-19 outbreak. Front Psychol 2020;11:2201

39. Moreno C, Wykes T, Galderisi S, Nordentoft M, Crossley N, Jones N, et al. How mental health care should change as a consequence of the COVID-19 pandemic. Lancet Psychiatry 2020;7:813-824.