The prevalence and incidence of treated major depressive disorder among National Health Insurance enrollees in Taiwan, 1996 to 2003

Objective: We used the National Health Insurance (NHI) database to examine the prevalence and incidence of treated major depressive disorder (MDD) and their associated factors. Method: The National Health Research Institute provided a database of 200 432 randomly selected subjects for study. We obtained a population-based random sample aged 15 years or older (n = 136 045) as a fixed cohort dated 1996 to 2003. We identified study subjects with a principal diagnosis of MDD who had at least one service claim during these years for either ambulatory or inpatient care. Results: From 1996 to 2003, the cumulative treated prevalence increased from 1.67 per 1000 to 17.24 per 1000. From 1997 to 2003, the annual treated incidence increased from 1.89 per 1000 to 2.58 per 1000. A higher incidence of treated MDD was detected in the groups aged 25 to 44 years (hazard ratio [HR] 1.28; 95% confidence interval [CI], 1.13 to 1.45), 45 to 64 years (HR 1.90; 95%CI, 1.66 to 2.16), and 65 years or older (HR 1.87; 95%CI, 1.59 to 2.20); in female subjects (HR 1.97; 95%CI, 1.80 to 2.15); in those with with an insurance amount of US$1281 or more (HR 1.15; 95%CI, 1.01 to 1.31); in those with a fixed premium (HR 1.44; 95%CI, 1.27 to 1.62); and among those who lived in urban areas (HR 1.22; 95%CI, 1.10 to 1.35). Conclusions: For treated MDD, the prevalence and incidence in Taiwan were lower than in community studies in Western countries. Individuals with MDD are underdiagnosed and undertreated in Taiwan.