Objectives The aim of this study is to investigate the incidence rate of depressive disorder, panic disorder and posttraumatic stress disorder (PTSD) and total prescription days with antidepressants using data from the National Health Insurance Service. Method Health insurance claims records were obtained from the Korea Health Insurance Review and Assessment Service database from 2014 to 2018. We identified the total number and incidence of patients first diagnosed with depressive disorder, panic disorder and PTSD and the sum of prescription days with antidepressants. Results The incidence rate per 1,000 people of depressive disorder increased from 3.53 in 2014 to 5.04 in 2018. Among patients who were first diagnosed with depression and prescribed antidepressants, the proportion of patients with 0-4 weeks of prescription days was 39%, 4 weeks-8 weeks 15%, 8 weeks-90 days 11% and over 90days 35%. The incidence rate per 1,000 people of panic disorder increased from 0.59 in 2014 to 1.10 in 2018. In panic disorder, the proportion of patients with 0-4 weeks of prescription days was 26%, 4 weeks-8 weeks 13%, 8 weeks-90 days 11% and over 90days 50%. The incidence rate per 1,000 people of PTSD increased from 0.08 in 2014 to 0.12 in 2018. In PTSD, the proportion of patients with 0-4 weeks of prescription days was 31%, 4 weeks-8 weeks 17%, 8 weeks-90 days 15% and over 90days 37%. Conclusion This result can be used as basic data for predicting the size of depressive disorder-related incidence and improving mental health policies for appropriate treatment.