Discussion

This study systematically described the disease burden of depressive and anxiety disorders in China and the different provinces from 1990 to 2021, based on GBD 2021. From 1990 to 2021, despite the age-standardised prevalence rates of anxiety disorders remaining stable and depressive disorders decreasing significantly, there was a substantial increase in the number of both depressive and anxiety disorder cases, with significant increases in DALYs. Females had higher prevalence of both depressive and anxiety disorders across all age groups. There were significant spatial variations in prevalence and DALYs rates across provinces. The outbreak of the COVID-19 pandemic increased the burden of depression and anxiety disorders in China.

The significant increase in the burden of depressive and anxiety disorders in China over the past three decades could be heavily driven by the substantial population growth and ageing. From 1990 to 2021, the Chinese population grew from 1.1 to 1.4 billion, with the proportion of the population aged 60 and above increasing from 8.6 to 18.9%.¹⁷ After accounting for the effects of population growth and ageing, the age-standardised rates of prevalence and DALYs showed no significant changes or a slight decrease. It is estimated that by 2040, the total number of older people in China will reach 400 million, accounting for 28% of the total population,¹⁸ which means the disease burden may further increase. Furthermore, the Chinese Mental Health Survey reported that the 12-month prevalence was 5.0% for any anxiety disorder and 3.6% for depressive disorders, while an epidemiological survey in four provinces (Shandong, Zhejiang, Qinghai and Gansu) of China reported that the prevalence was as high as 5.6% for anxiety disorders, 2.1% for MDD and 2.0% for dysthymia,^{Reference Huang, Wang, Wang, Liu, Yu and Yan7,Reference Phillips, Zhang, Shi, Song, Ding and Pang19} both conducted before the COVID-19 pandemic. Compared to these studies, our estimates were likely to be highly underestimated. This would be mainly attributed to the methodology of calculating prevalence in the GBD database, where the calculation of the prevalence rate involves dividing the total number of cases within a specific population over a 2-week period by the total population size, known as point prevalence. In contrast, most previous studies have reported 12-month prevalence or lifetime prevalence, both of which have been used more frequently. It suggested that mental health conditions in depressive and anxiety disorders did not improve over the past three decades and the burden is expected to continuously increase in the number of cases and DALYs with the process of ageing if no measures are taken.

In China, there are significant disparities in the disease burden of depressive and anxiety disorders across different genders and age groups. Consistent with studies globally and nationally, we found that depressive disorders and anxiety disorders were more common in females across all age groups.^{Reference Huang, Wang, Wang, Liu, Yu and Yan7,20,Reference Yan, Zhang, Wang, Yan, Liu and Tian21} The gender disparity may be partly explained by some biological and psychological factors, such as females being more affected by genetic risk markers and being subject to the influence of sex hormones, neuroticism and poor stress response.^{Reference Christiansen22,Reference Kuehner23} In addition, environmental drivers, including experiences of gender inequality, internal and external stressors, sexual abuse and violence, may also contribute to the disparity.^{Reference Christiansen22,Reference Kuehner23} The current literature has suggested ongoing gender inequalities in China, driven by a variety of unequal social norms that favour males (particularly in rural regions),^{Reference Hu, Guo and Ding24} imposing a long-lasting negative influence on females in various life stages, with fewer job opportunities, relatively lower wages and challenges in gaining promotions.^{Reference Artazcoz, Borrell, Cortès, Escribà-Agüir and Cascant25} For specific age groups, our findings showed that depressive and anxiety disorders, particularly MDD, were highly prevalent in older age groups. Similar to the findings of this study, our previous research has showed the consistent pattern that MDD is more common among the elderly population globally.^{Reference Yan, Zhang, Wang, Yan, Liu and Tian21} This would be partly associated with the higher prevalence of chronic diseases, lower income, social isolation, empty-nest situations (elderly people whose children have grown up and moved out, often leaving them living alone) and physical and mental abuse among the elderly.^{Reference Zhang, Xue, Zhao, Zheng, Zhu and Du26–Reference Yan, Zhang, Yan, Zhang, Li and Liu28} Notably, there is a lack of attention to the management of mental disorders among the elderly. Only severe mental disorders, such as schizophrenia and bipolar disorder, have been included in the National Essential Public Health Service in China,²⁹ while depression and anxiety disorders do not have standardised management guidelines, warranting further efforts in both research and policies.

Anxiety disorders contributed a high proportion of DALYs under all mental disorders in ages 5–24 years in China, which may be related to academic pressure from schools,^{Reference Steare, Gutiérrez Muñoz, Sullivan and Lewis30} being neglected and left behind (children who remain in rural areas while their parents migrate to urban areas for work, often leading to prolonged separations)^{Reference Fellmeth, Rose-Clarke, Zhao, Busert, Zheng and Massazza31} and bullying victimisation.^{Reference Balluerka, Aliri, Goñi-Balentziaga and Gorostiaga32} Experiencing anxiety disorders during childhood could increase the risk of anxiety and other mental disorders in adulthood, which is detrimental to the lifelong health and well-being of the population. To alleviate the excessive homework burden and reduce off-campus tutoring for Chinese school students, the General Office of the Central Committee of the Communist Party of China and the General Office of the State Council jointly issued the ‘Double Reduction Plan’ in 2021 to promote the all-around development and healthy growth of students under compulsory education.³³ The extent to which these measures can mitigate anxiety in students and foster their holistic well-being warrants empirical investigation, thereby informing evidence-based practices.

The burden of depressive and anxiety disorders varies significantly among provinces in China. The highest prevalence of anxiety disorders was found in Hunan, while the highest prevalence of depressive disorders was in Hong Kong, Zhejiang and Shandong, all being economically developed provinces. However, aside from these observations, no significant differences in depressive and anxiety disorders were found between areas with varying levels of economic development. Conversely, our previous study found that, at the global level, low sociodemographic index countries had the highest prevalence of MDD.^{Reference Yan, Zhang, Wang, Yan, Liu and Tian21} This may be because these countries still face severe social issues such as extreme poverty, starvation and war, whereas the most underdeveloped regions in China do not have these problems. Hunan province has one of the most well-known specialised institutions for mental disorders in China, the Department of Psychiatry at the Second Xiangya Hospital of Central South University. This institution has high visibility and handles nearly 170 000 out-patient visits annually, which may lead to potential detection bias. The Special Administrative Region of Hong Kong has the highest burden of depressive disorder, driven by MDD, with its burden being approximately 2.2 times that of Tianjin, which has the lowest burden. A study reported that from 2009 to 2019, the prevalence of MDD among adults in Hong Kong increased by 5.9 times (from 1.9 to 11.2%).^{Reference Ni, Yao, Leung, Yau, Leung and Lun34} The unstable social environment and inappropriate use of social media (such as extreme content, fake news and emotional contagion) were supposed to be significant contributors to the increased burden of MDD during this period.^{Reference Ni, Yao, Leung, Yau, Leung and Lun34} Meanwhile, because of disparities in the healthcare systems and levels of economic development between the Special Administrative Regions of Hong Kong and Macau and mainland China, this may lead to variations and incomparability in disease burdens to some extent. Researchers are expected to conduct systematic analyses of the reasons for regional disparities to assist government and policymakers in developing tailored interventions accordingly.

The emergence of the COVID-19 pandemic has reversed the declining trend of the prevalence of depressive and anxiety disorders in China, with the absolute disease burden of the number of cases and DALYs increasing more rapidly. Globally, the burden of depressive and anxiety disorders significantly increased in 2020 because of the COVID-19 outbreak, with an estimated 53.2 million cases of MDD and 76.2 million cases of anxiety disorders throughout this year.³ However, the percentage change in the prevalence of MDD and anxiety disorders in China remained relatively lower compared to global levels.³ Several studies have analysed the potential reasons for this phenomenon observed in the early stages of the pandemic, such as timely implementation of prevention and control measures by the Chinese government, provision of COVID-19-related health information, integration of psychological intervention measures into epidemic-related work and public acceptance of personal preventive measures (e.g. wearing face masks).^{Reference Qiu, Shen, Zhao, Wang, Xie and Xu35–Reference Wang, Tripp, Sears, Xu, Tan and Zhou38} Furthermore, some long-term effects caused by COVID-19, such as high risk of unemployment and depressed economic and social circumstances, also might increase the disease burden. During this period of pandemic, the negative effects of COVID-19 on mental illnesses were pervasive across the entire population, with high-risk and vulnerable groups, including children and adolescents, the elderly, COVID-19 patients and healthcare staff,^{Reference Chen, Liang, Li, Guo, Fei and Wang39–Reference Chen, Qi, Liu, Feng, Li and Xiang42} being more likely to be affected and requiring more attention and support. Notably, there was a wider uncertainty in the all estimates after 2019, requiring more accurate information to assess the mental health of the public during this period. Governments and policymakers need to strengthen mental health service systems to address the current unmet mental health needs and to improve reliable and efficient response strategies for future public health emergencies.

The general limitations of GBD have been extensively documented,^10,11 and here we primarily discuss the special limitations. First, the lack of high-quality provincial-level epidemiological data is a prevalent issue, particularly in economically underdeveloped regions. Despite systematic and comprehensive GBD estimation methods, the potential bias resulting from data gaps cannot be entirely eliminated. Second, substantial disparities in economic conditions and healthcare infrastructure across Chinese provinces, coupled with inadequate diagnostic capabilities and low accessibility to medical resources in underdeveloped areas, may introduce measurement biases. Third, heterogeneity resulting from variations in study designs, sampling methods, diagnostic criteria and capacities of investigation also increases the biases in estimating disease burden. Fourth, the increased estimation error of disease burden in 2021 compared to previous years poses challenges to the reliability of research outcomes and is unfavourable for evidence-based epidemic prevention, health policy formulation and decision-making. Finally, the methodological limitations of GBD 2021, along with issues related to data accessibility, resulted in potential underestimation of disease burden in certain populations and a lack of information in mortality and risk factors. This includes the underestimation of disease burden in specific age groups (less than 3 years old or above 95 years old) and the underestimation of YLLs, in addition the failure to provide information on the disease burden associated with specific anxiety disorders and identify other attributed risk factors associated with depressive and anxiety disorders.

In summary, our research indicates that depressive and anxiety disorders are important contributors to the disease burden in China. Between 1990 and 2021, the age-standardised prevalence and DALY rates of depressive and anxiety disorders showed no markable changes, but there was a significant increase in the number of cases and DALYs. The outbreak of the COVID-19 pandemic exacerbated the disease burden on depressive and anxiety disorders, particularly dysthymia and anxiety disorders. Significant disparities in disease burden exist across different genders, age groups and provinces. With the rapid ageing population in China, governments at all levels need to consider the allocation of more healthcare resources to address the increasing mental health issues. In addition, more robust research is urgently needed to provide reliable evidence on understanding the epidemiology and developing effective interventions to combat this growing burden of depressive and anxiety disorders in China.