Changes in the Mean of and Variance in Psychological Disease Incidences before and during the COVID-19 Pandemic in the Korean Adult Population

The coronavirus disease 2019 (COVID-19) pandemic has been suggested to increase the risk of depression and anxiety disorders. This study expanded upon previous findings by estimating the changes in medical visits for various psychological disorders during the COVID-19 pandemic compared to before COVID-19. The entire Korean population ≥ 20 years old (~42.3 million) was included. The first COVID-19 case in Korea was reported on 20 January 2020. Thus, the period from January 2018 through to February 2020 was classified as “before COVID-19”, and the period from March 2020 through to May 2021 was classified as “during COVID-19”. Monthly medical visits due to the following 13 psychological disorders were evaluated: depressive disorder, bipolar disorder, primary insomnia, schizophrenia, panic disorder, hypochondriasis, posttraumatic stress disorder (PTSD), anxiety disorder, anorexia nervosa, addephagia, alcoholism, nicotine dependency, and gambling addiction were evaluated. The differences in the number of medical visits and the variance of diseases before and during the COVID-19 pandemic were analyzed using the Mann–Whitney U test and Levene’s test. Subgroup analyses were conducted according to age and sex. The frequencies of medical visits for depressive disorder, bipolar disorder, primary insomnia, panic disorder, hypochondriasis, PTSD, anxiety disorder, anorexia nervosa, addephagia, and gambling addiction were higher during COVID-19 than before COVID-19 (all p < 0.001). However, the frequencies of medical visits for schizophrenia, alcoholism, and nicotine dependency were lower during the COVID-19 pandemic than before the COVID-19 pandemic (all p < 0.001). The psychological disorders with a higher frequency of medical visits during COVID-19 were consistent in all age and sex subgroups. In the old age group, the number of medical visits due to schizophrenia was also higher during COVID-19 than before COVID-19 (p < 0.001). Many psychological disorders, including depressive disorder, bipolar disorder, primary insomnia, panic disorder, hypochondriasis, PTSD, anxiety disorder, anorexia nervosa, addephagia, and gambling addiction, had a higher number of related medical visits, while disorders such as schizophrenia, alcoholism, and nicotine dependency had a lower number of related medical visits during COVID-19 among Korean adults.