Our study results showed that during the COVID-19 pandemic, about one in five members of the general population who were not infected had clinically significant depression. Thus, the prevalence of depression was rather high. The risk of depression was increased in people suffering from loneliness and COVID-19-related stress, people who experienced psycho-behavioural changes such as disturbances in eating and sleeping, smokers, people with underlying mental illness, and those who were younger. However, regular exercise and attitudes of gratitude were inversely associated with depression. Our study demonstrated that psychosocial changes and COVID-19-related stress increased the risk of depression and suggested that maintaining life routines such as regular exercise, eating, and sleeping and positive mind may be helpful in preventing depression during these COVID-19 times.
The prevalence of depression (21%) found in this study was similar to that of previous reports about depression prevalence (PHQ-9 ≥ 10) during the COVID-19 pandemic in the US, Europe, and Asian countries (14.4–27.8%) [2, 12, 13]. According to the 2019 Korea Community Health Survey, the prevalence of depression in Korea, using the PHQ-9, was only 4.3% in 2018 [14]. Although there are limitations to comparing subjects and methods directly across studies, our results, showing an approximately fivefold increase in the prevalence of depression, suggest that psychosocial changes induced by the COVID-19 pandemic increased the risk of depression. The development of psychosocial strategies for the prevention of depression is urgently needed. For this, we should first understand the pathogenesis of, and factors associated with depression in COVID-19 pandemic societies.
In this study, the stress associated with psychosocial changes due to COVID-19 was significantly associated with increased risks of depression. In development of COVID-19 vaccines, social distancing and restricted economic activities are likely to continue. However, disturbances of sleep and eating patterns related to COVID-19, which were also significantly associated with increased risks of depression, might be more easily modified at a personal level. While a causal relationship is unclear, the inverse relationship between regular exercise during the pandemic and depression suggests that maintaining healthy lifestyles like regular exercise, eating habits, and sleep patterns daily may be important tools for preventing depression in the COVID-19 era [15] by improving mental and physical health.
Loneliness was strongly associated with the risk of depression in this study. Although social distancing is effective in preventing the coronavirus spread, it can cause loneliness due to emotional disconnection [13]. Despite long-lasting and inevitable social distancing policies, social and emotional interactions may reduce impacts of loneliness on depression.
Gratitude was inversely associated with depression. Gratitude has been reported as a protective factor against depressive symptoms following traumatic events [16]. At societal levels, gratitude is also important in forming and maintaining social relationships and encouraging people to be more prosocial [17]. Our results suggest that, during this COVID-19 pandemic, people are experiencing social isolation and loneliness, gratitude can be a psychological antidote to depression by reinforcing social bonds as well as positive mood. A recent study showed that positive attitudes reduced the negative effects of COVID-19 on mental health among Wuhan college students [18]. Although the COVID-19 pandemic and associated societal changes are drastically influencing our lives, positive attitudes and a sense of gratitude are likely to be helpful in preventing depression.
Socially and mentally vulnerable populations, such as the unemployed or temporary workers as well as people with underlying psychiatric illnesses, were more likely to have current significant depressive symptoms, although employment status was no longer significant in the adjusted analysis. The younger generation tended to be at greater risks of depression. Generally, the prevalence of depression is higher in middle aged and elderly people [19]. However, many recent studies have found that young people were more vulnerable to mental health problems during the COVID-19 pandemic era [13, 20, 21]. Current drastic social changes may have greater impacts on the younger generation, whose psychological resilience and established social base may be inadequate for this situation. They may experience greater fear and worry about their future while living in this socioeconomically unstable society. In addition, young people are at greater risks for emerging psychiatric problems. Taken together, these results indicate that populations who are psychosocially vulnerable may be more severely affected by the distress associated with COVID-19. Therefore, we should observe these vulnerable populations carefully to facilitate early detection of mental health problems and to provide more active support.
Cigarette smoking is reportedly associated with increased risks of depression [22]. Recent studies investigating factors associated with depression also showed that smoking was associated with depression during the COVID-19 pandemic [23]. Both the biological impacts of smoking on neurotransmitters and vascular health [24] and the psychosocial influence of this respiratory pandemic on smokers should be considered as factors in the pathogenesis of depression in smokers.
This study has several limitations. First, we should be careful in applying our results to other populations affected by COVID-19. Second, causal relationships are uncertain because this study was cross-sectional. Longitudinal studies are needed to investigate the risks and protective factors of depression associated with the COVID-19 pandemic. Finally, results via an online survey method may differ from those acquired through face-to-face surveys, and there is a potential for selection bias. Therefore, caution is required when comparing the results of online and face-to-face surveys.