Incidence trends of major depressive disorder in China: an age-period-cohort modeling study

Background: Major depressive disorder (MDD) is a common public health problem in China. However, few studies have focused on its incidence and separated age, period, and cohort effects. This study aimed to assess the age, period, and cohort effects on the incidence trends of MDD in China between 1993 and 2017. Methods: The incidence data of MDD were obtained from the Global Burden of Diseases Study 2017. Age-periodcohort modeling method was used to separate the age, period, and cohort effects on MDD incidence rate. Results: The incidence number of MDD increased by 22.8% while the age-standardized incidence rate decreased by 15.6% over 25 years. Age-period-cohort analysis indicated that the net drift was -0.433% per year, with -0.486% for females and -0.385% for males. For both sexes, the local drifts were all 0 in 10 to 54 years age groups but 0 in 55 to 94 years age groups. The longitudinal age curves of MDD incidence basically showed an increasing trend, except for a subpeak at 20-24 years age group. The period rate ratio largely declined over time, except for an uptick after 2003-2007. The cohort rate ratio followed an inverted U-shaped pattern and was highest in 1951-1955 birth cohort. Limitations: The MDD data were estimated and wide social factors were not included in the analyses. Conclusion: The changes of MDD incidence rate in China are likely to be related to rapid social and economic development, and major historical events. However, the associations need to be interpreted with caution.