The COVID-19 pandemic has caused widespread psychosocial distress, including increased depression, due to social isolation, economic stress, and fear of infection. Individuals with pre-existing mental illnesses, such as schizophrenia, are particularly vulnerable. Schizophrenia patients often experience functional impairments and limited social interaction, making them more susceptible to the negative impacts of pandemic restrictions. Social distancing policies and fear of infection may further isolate them from crucial social support networks and access to essential medical and mental health resources. Previous research has primarily focused on the general population's mental health during the pandemic, with limited studies on schizophrenia patients. This study aimed to investigate the differences in psychosocial stress and mental health patterns between schizophrenia patients and the general population during the COVID-19 pandemic. The hypotheses were: (1) high levels of psychological distress and depression in schizophrenia patients during the pandemic, and (2) differing pathways leading to depression between the two groups. Structural equation modeling (SEM) and latent mean analysis were employed to compare key psychological variables, including COVID-19-related stress, fear of infection, loneliness, and depression.

Existing literature highlights the significant mental health consequences of infectious disease outbreaks, with COVID-19 exacerbating these effects in the general population. Studies show increased rates of depression, anxiety, and stress due to pandemic-related factors. However, research specifically addressing the mental health of individuals with schizophrenia during the pandemic remains limited. While some studies suggest increased vulnerability to COVID-19 infection and mortality in schizophrenia patients, the specific impacts of pandemic-related stress and fear on their mental well-being need further investigation. This gap in the literature underscores the importance of this study, which aims to fill this gap by comparing the mental health experiences of individuals with schizophrenia to the general population.

This study involved two separate surveys: a face-to-face survey of 1340 patients with a schizophrenia-spectrum disorder and an online survey of 2000 individuals from the general population. Both surveys were conducted in Korea between April and July 2020, during the initial stages of the COVID-19 pandemic. The face-to-face format was chosen for the schizophrenia patient group due to potential limitations in their comfort levels with online platforms. The surveys collected data on sociodemographic characteristics (age, gender, marital status, education, employment), depression (Patient Health Questionnaire-9; PHQ-9), loneliness (UCLA Loneliness Scale), and COVID-19-related stress and fear of infection (a researcher-developed and validated questionnaire). Data analysis included Cronbach's alpha for scale reliability, normality checks, latent mean analysis (to compare latent variable means between groups, accounting for measurement error), and structural equation modeling (SEM) to examine direct and indirect effects among variables (stress, fear, loneliness, and depression). Invariance testing was conducted to ensure the comparability of the latent variables across groups. The SEM used CFI, TLI, and RMSEA indices to evaluate model fit. The bootstrapping method was used to assess the significance of mediating effects. Sociodemographic variables were included as controls in the analysis of direct and indirect effects.

The study found no significant difference in age or sex between the schizophrenia patient group and the general population. However, schizophrenia patients were more likely to be single, unemployed, and less educated. Latent mean analysis revealed that while schizophrenia patients exhibited significantly lower levels of COVID-19-related stress and fear of infection than the general population, they experienced significantly higher levels of loneliness and depression. The effect sizes were large for COVID-19 stress, medium for fear of infection and loneliness, and small for depression in schizophrenia patients compared to the general population. SEM analysis showed that the effect of fear of infection on depression was significant in the general population but not in schizophrenia patients. Conversely, the effect of fear of infection on loneliness was significant in the schizophrenia patient group but not in the general population. The effect of loneliness on depression was significant in both groups. Importantly, loneliness significantly mediated the relationship between COVID-19 stress and depression in both groups (partial mediating effect). However, loneliness fully mediated the relationship between fear of infection and depression only in the schizophrenia patient group. Analysis controlling for sociodemographic factors showed that older age increased fear of infection in both groups, while younger age was associated with higher loneliness and depression in the general population. Among schizophrenia patients, marital status and occupation affected loneliness, while occupation and education level influenced depression.

The findings indicate that while COVID-19-related stress and fear were less pronounced in schizophrenia patients than in the general population, loneliness emerged as a significant mediating factor leading to heightened depression in both groups, particularly among schizophrenia patients. This suggests that pre-existing social isolation and limited support systems in schizophrenia patients make them exceptionally vulnerable to the pandemic's impact. The lower levels of reported stress and fear among schizophrenia patients may be attributed to existing pre-pandemic mental health challenges overshadowing the pandemic-related stressors, or a different attribution of their feelings. The study emphasizes the critical need for tailored mental health interventions for schizophrenia patients, targeting loneliness reduction and improved social support systems.

Loneliness, significantly mediated by COVID-19-related stress and fear, played a crucial role in exacerbating depression in both schizophrenia patients and the general population, with a greater impact on the former. Enhanced social support and mental health services are essential for mitigating loneliness and subsequent depression among schizophrenia patients during and after the pandemic. Future research should explore other mediating factors, utilize consistent survey methods, consider diverse cultural contexts, and employ longitudinal studies to ascertain causal relationships and long-term effects.

The study's limitations include the focus on loneliness as the sole mediating factor, potential differences in response patterns between face-to-face and online surveys, the study's cross-sectional design (preventing causal inferences), and the specific context of South Korea's COVID-19 response (which might not fully generalize to other settings). Future research should address these limitations by examining a broader range of mediating factors, using consistent survey methodologies, and adopting longitudinal designs.