Background: The COVID-19 pandemic has triggered a global mental health crisis. According to WHO estimates, anxiety and depression rose by 25% in the first year. In the post-COVID era, over 70% of patients experience depression, anxiety, insomnia, PTSD, and OCD, which can persist for up to 24 months. Hospitalized individuals face heightened risks due to infection severity, treatment stress, and social isolation. However, studies examining treatment outcomes and influencing factors remain limited. In Mongolia, mental health issues escalated sharply from 2020 to 2022; WHO data indicate that anxiety and stress were prevalent among healthcare workers and patients. Children and youth were particularly affected, with UNICEF studies emphasizing the urgent need for intervention. Suicide rates increased from 18.3 per 100,000. Long-term research on post-COVID mental disorders is scarce, impeding policy formulation. This study evaluates treatment outcomes in COVID patients and identifies key factors. By comparing case and control groups at 3 and 12 months, it uncovers differences in symptoms and treatment responses. The comparative design assesses statistical significance via P-values and subgroup success rates for CBT and SSRI therapies. Findings will enhance Mongolia’s mental health services. Larger-scale studies are essential moving forward. Objective: To evaluate treatment outcomes for post-COVID mental disorders and identify influencing factors. To analyze differences in psychological symptoms and treatment between case (COVID-19 positive) and control groups over 3 and 12 months. Material and Method: Retrospective comparative analysis of records from 281 patients (cases n=181, controls n=100) at a unified hospital from 2020-2022. At 12 months, n=200 (cases n=100, controls n=100). Patients were categorized by anxiety, depression, insomnia, and stress-related symptoms, with P-values calculated. Detailed subgroup analysis (n=47 treated patients) was conducted. Results: At 3 months, cases showed higher anxiety (56.4%, P=0.002), depression (41.4%, P<0.001), and insomnia (58%, P=0.107). At 12 months, differences lessened but anxiety (52%, P=0.023) and depression (35%, P=0.042) remained significant. COVID-related new symptoms were elevated in cases (e.g., depression 24.3%, P<0.001). Treatment subgroup success was 95.7% (P<0.001), with duration influencing outcomes (P=0.03). Conclusion Post-COVID mental symptoms persist long-term in cases, and extended treatment durations yield better results. Larger studies are required