Introduction

China, with 18% of the world’s population, has undergone significant economic and institutional changes over the past three decades. As such, it serves as an excellent research sample for other develo** countries and the world as a whole. Despite its rapid economic development, China faces social issues like increasing competitive pressure, rising medical costs, widening poverty gaps, and increasing psychological stress, which have contributed to a rise in the incidence of depression over time [1, 2]. This trend has posed a serious threat to society and personal lives [3], necessitating the urgent need to understand the epidemic trend of depressive disorders and develop effective strategies to address them.

While major depressive disorder (MDD) is often the focus of attention due to its severity and short-term effects, another subtype of depression, dysthymia, is frequently overlooked [4, 5]. Dysthymia, defined by the ICD-10 as a persistent depressive mood lasting for more than two years and with lower severity than MDD, is associated with significantly impaired quality of life, despite its milder symptoms [6]. For instance, individuals with dysthymia exhibit lower rates of full-time employment and are more likely to depend on public assistance compared to the general population and individuals with MDD [7]. Moreover, dysthymia is characterized by higher prevalence in the general population, greater childhood adversity, more functional impairment, and a higher risk for suicide attempts [8]. Compared to the episodic form of MDD, dysthymia is associated with more severe life damage and higher social and economic costs [9]. Thus, analyzing the differences between MDD and dysthymia may yield more disease phenotypes for exploratory research on etiology and treatment [8]. However, comparative research data on MDD and dysthymia remain scarce [8].

Currently, the pathogenesis of depression remains unclear and its high recurrence rate continues to pose a significant treatment burden. Ren et al. reported that the prevalence and DALY rate of depression had increased to varying degrees across all age groups in China from 1990 to 2017 [2]. However, their study only analyzed the prevalence and DALYs of depression by age, gender, and province. Yueqin Huang et al. conducted a cross-sectional epidemiological survey of the prevalence of adult depression in 157 nationwide representative population-based disease surveillance points in 31 provinces in China [2]. The results showed a lifetime weighted prevalence of 3.4% for MDD and 1.4% for dysthymia. However, dysthymia is considered to be equally disabling and clinically severe as MDD. Therefore, the identification, prevention, and treatment of dysthymia should be considered as important as that of MDD. Alarmingly, only 9.5% of the 1007 participants with depressive disorders used mental health services and only 0.5% of those with depressive disorders received adequate treatment. Therefore, detailed epidemiological characteristics of MDD and dysthymia, especially risk factors, are important to improve treatment engagement and reduce the burden of disease [10].

However, few studies have thoroughly assessed, compared, and projected the burden of MDD and dysthymia, along with their risk factors, in China. Such studies could greatly assist in the formulation of policies for preventing and managing depressive disorders. For example, the significant increase in disability-adjusted life years(DALYs) of MDD attributable to bullying victimization over the last three decades requires extra attention [11]. Additionally, a possible causal relationship between bullying victimization and depressive disorders has been suggested [12]. Bullying victimization not only increases the risk of mental disorders but also carries significant direct costs for individuals and society as a whole [13]. Unfortunately, the burden of disease resulting from bullying victimization was not assessed until the Global Burden of Disease (GBD) 2017.

The aim of this study is to evaluate and compare the burden of MDD and dysthymia in China from 1990 to 2019, including temporal trends by age, sex, disease subtypes, and risk factors. Furthermore, this study seeks to project the burden of dysthymia and MDD separately from 2020 to 2030. This research can aid in the evaluation of current prevention strategies and provide additional theoretical support for their revision.

Methods

Depression definition and data sources

All data and analyses presented in this study were based on the GBD Study 2019, which provides estimates of incidence, prevalence, deaths, and DALYs in different countries and regions from 1990 to 2019. The GBD Study employs meticulous methods that have been described in detail in earlier publications [14, 15]. Using the Diagnostic and Statistical Manual IV (DSM-4) and the International Classification of Diseases 10th revision (ICD-10), the GBD Study examined two major categories of depression: MDD and dysthymia. The codes used to identify depressive disorders were DSM-IV-TR: 296.21-24, 296.31-34, 300.4 and ICD-10: F32.0-9, F33.0-9, F34.1, which covered MDD and dysthymia and excluded cases due to general medical conditions or substance use. To estimate the prevalence, incidence, duration, and excess fatality associated with depressive disorders, the GBD Study conducted a comprehensive search of PsycInfo, Embase, PubMed, the grey literature, and consulted with experts. A total of 517 and 107 original data sources were collected for MDD and dysthymia, respectively, to enable global assessment of depressive disorders. Detailed information on the search strategies, methodologies, and estimation of depression can be found on the GBD Study website (http://ghdx.healthdata.org/gbd-2019).

To analyze the burden of depressive disorders in China, we utilized the GBD database and selected China as the location, “depressive disorder” as the cause, and “incidence,” “prevalence,” and “DALYs” as measures. The DALYs were computed by adding disability-adjusted life years (YLDs) and YLLs years of life lost (YLLs) in GBD study. Because depressive disorders are nonfatal disease, the DALYs due to depressive disorders are equivalent to the YLDs, which were computed by sequela as prevalence multiplied by the disability weights (DW) for the health state associated with that sequela [14]. In calculating the 95% uncertainty intervals (UIs), we utilized the 25th and 975th ordered percentiles of 1,000 random draws in the GBD study. Age-standardized rates for the incidence, prevalence, and DALYs of depressive disorders were calculated using the World Health Organization (WHO) World Standard Population Distribution (2000–2025). Additionally, the United Nations World Population Prospects 2019 Revision was used to predict the population.

Ethics approval and consent to participate

The authors confirm that this study was conducted in compliance with the ethical standards set by national and institutional committees on human experimentation, as well as the Helsinki Declaration of 1975 (revised in 2008). The study was approved by the Ethics Committee of Qilu Hospital of Shandong University (approval number KYLL-202,011(KS)-239). As the GBD 2019 study is a public database with all data being anonymous, no further ethical approval was required for this study.

Data analysis

This study aimed to describe the shift in incidence, prevalence, and DALYs of depressive disorders in China from 1990 to 2019, with all cases divided into 5-year age groups. The average annual percentage change (AAPC) was calculated to quantify temporal trends of incidence, prevalence, and DALYs [16,17,18]. The regression line was fitted to the natural logarithm of the rates, i.e., y = α + βx + ɛ, where y = ln (rate) and x = calendar year, and the AAPC was calculated as 100 × (exp(β)-1). A 95% confidence interval (CI) of AAPC was also computed. To estimate the proportion of DALYs attributed to potential risk factors, the comparative risk assessment (CRA) framework and three well-established risk factors for depressive disorders (bullying victimization, child sexual violence, and intimate partner violence) estimated in the GBD 2019 study were applied in the present study [15]. According to the World Cancer Research Fund grades of convincing or probable evidence, intimate partner violence, bullying victimization and childhood sexual abuse were identified as attributable risk factors of MDD. The disease burden attributable to risk factors was estimated the following six key steps: inclusion of risk–outcome pairs in the analysis; estimation of relative risk as a function of exposure; estimation of exposure levels and distributions; determination of the counterfactual level of exposure, the level of exposure with minimum risk called the theoretical minimum risk exposure level (TMREL); computation of population attributable fractions and attributable burden; and estimation of mediation of different risk factors through other risk factors [19]. Bayesian age-period-cohort analysis with integrated nested Laplace approximation was used to project the numbers of cases, prevalence, and DALYs for depressive disorders by disease subtypes from 2020 to 2030. This method has been proven to have better accuracy in forecasting non-communicable diseases, especially in non-longer projection years, compared with other models [36]. The socio-cultural environment in China can lead to the elderly perceiving themselves as a burden to their families and society, which may gradually lead to depression [37]. Furthermore, there is often a long-term depression around retirement age, and compared to retiring or being inactive, working in the long-term is associated with lower depressive symptoms [38]. With the impact of the “one-child policy” and the rapid aging of the population, the burden of disease is expected to increase in the future.

The results of present study showed that intimate partner violence was the most significant contributor to the burden of depression in China, followed by bullying victimization and child sexual violence. In recent years, the level of intimate partner violence has gradually increased in China, which can lead to victims’ feelings of fear, helplessness, powerlessness, and isolation [39]. Meta-analyses have indicated that the prevalence of depression is high among women who have experienced psychological violence (65.8%), physical violence (69.5%), and sexual violence (75.8%) [40]. The study also confirmed that the tendency of young women to suffer from intimate partner violence has decreased in the past decades but has increased in recent years. In China, the DALYs rate per 10,000 elderly women suffering from intimate partner violence has unexpectedly increased in recent years. This could be due to the social status of women and increasing economic stress, which predisposes them to anger, frustration, and manifestations of violence [41, 42]. These economic pressures, and the resulting changes in perception, ultimately lead to a higher risk of intimate partner violence. Furthermore, bullying victimization, which commonly occurs among school-aged children, is a salient stressor that leads to deficits in emotion regulation across the lifespan [43]. There is strong evidence that bullying victimization is associated with suicidal ideation and attempts and that depression is a major undesirable outcome. Depression was found to be a moderator between bullying and suicidality [44,45,46]. In addition, the estimated prevalence of child sexual violence among males and females in China was 9.1% and 8.9%, respectively. The prevalence of male child sexual violence in China is higher than the global prevalence (7.9%) [47, 48]. Childhood sexual violence has negative effects on victims’ physical and mental health and is associated with an increased risk of depression [49]. Although the risk of child sexual violence has remained stable from 1990 to 2019, the problem still needs to be taken seriously. Early intervention to identify and support victims of life trauma could prevent the development of nasty conditions.

According to the WHO, depressive disorders are one of the leading causes of disability worldwide and contribute to the global burden of disease, accounting for about 46.9 million DALYs in 2019 [14]. However, in China, ASIR, ASPR, and ASDR are lower than in numerous developed countries. It is possible that this data is underestimated due to stigma and/or lack of mental health knowledge. Only 9.5% of people with depressive disorders used mental health services [10], much lower than in the United States (57.3% for MDD) [50] and other high-income countries [51], which confirms this speculation. Moreover, the uneven distribution of healthcare resources in China, especially the shortage of mental health services and inadequate training of mental health workers in western rural areas, has led to low diagnosis rates of depressive disorders [52]. Patients with depression often prefer to visit local tertiary or secondary general hospitals first, rather than a psychiatric specialist. Additionally, the Chinese are more likely to seek help from physicians in traditional Chinese medicine, resulting in some depressed patients being diagnosed with “mental disorders” instead of depressive disorders [10]. Furthermore, among depressed patients who first seek treatment in psychiatric hospitals, the number of those who worsen due to poor treatment or excessive medical expenses is staggering, leading to a waste of medical resources [53]. Therefore, the media, schools, and communities should strengthen mental health education and popularize relevant knowledge for the public in China. Moreover, psychological consulting and therapy should be a conventional procedure added to the therapy process of depressive disorders. Especially since the aging population is growing fast, the higher incidence rates of depression among the elderly remind us of the need to pay special attention to this group. It is meaningful to create a friendly social environment for the elderly and establish a positive attitude towards aging in the whole society [54]. Therefore, it is essential that the allocation of medical resources in China be based on the demographic characteristics of the disease burden.

Limitations

While this study sheds light on the burden of depression in China, there are some limitations to consider. Firstly, the estimates provided in GBD 2019 are based on mathematical modeling, and further research is needed to reflect a more realistic burden of disease. Secondly, depression in China carries a significant social stigma that can lead to underdiagnosis and may skew the estimated burden of depression in the country. Thirdly, this study only analyzed the national disease burden of depression and did not investigate the prevalence, incidence, DALYs, and risk factors of depression in different provincial or economic regions of China. Future research should focus on addressing these limitations to provide a more comprehensive picture of depression in China.

Conclusion

In conclusion, it is evident that the burden of depressive disorders in China has been increasing over the past 30 years due to various factors such as a large population, aging, economic pressures, and poor treatment, and it is expected to continue increasing in the future. Dysthymia, which was previously overlooked, is now receiving more attention due to its similar disability and clinical severity as MDD, and the detection rate of dysthymia is gradually increasing, leading to a shift in the subtypes of depressive disorders. MDD has seen a decrease in all age-standardized indicators, and the peak population of patients tends to be older, while dysthymia has remained relatively stable. It is crucial to establish targeted prevention and treatment strategies based on the existing population structure and risk factors. These strategies should focus on early identification and treatment of dysthymia, mental health education, attention to population aging, and early intervention for individuals suffering from life trauma. By implementing these multiple strategies, the burden of depressive disorders can be reduced in China.