RESEARCH WEEKLY: Global Burden of Severe Mental Illness
By Elizabeth Sinclair Hancq
The Global Burden of Disease (GBD) is a comprehensive global research effort to analyze the prevalence and disease burden of 286 causes of death, 369 diseases and injuries, and 87 health risk factors in 204 countries around the world. Incorporated in this research effort is an analysis of mental health disorders, including severe mental illness such as schizophrenia and bipolar disorder.
The GBD utilizes a variety of epidemiological health metrics to understand the burden of particular diseases on the world:
- Disability-adjusted life years (DALYs): One DALY represents one year lost in full health. Includes the sum of years having lived with a disability or ill-health and years of life lost due to that disability or disease.
- Years lived with disability (YLD): The equivalent of one full year of health lost due to a disability or ill-health.
- Years of life lost (YLL): A measure of premature mortality that considers the frequency of deaths due to a particular disease as well as the age of which such deaths occur, compared to the average life expectancy of that region.
A group of international collaborators on the GBD of mental health disorders published a paper in Lancet Psychiatry earlier this year utilizing the GBD data to examine the disease burden of various mental health conditions throughout the world. The study authors sought to measure global, regional and national estimates of prevalence, DALYs, YLDs, and YLLs for mental illnesses from 1990 to 2019.
GBD results
Mental health conditions represent some of the leading causes of disability and disease burden across the world, according to the results. Additionally, the results indicate that the burden of mental illness on society is only getting worse, suggesting the increased importance for governments to address the mental health treatment gaps experienced globally.
Prevalence
Between 2009 and 2019, the global age-standardized prevalence rate of schizophrenia and bipolar disorder remained relatively unchanged. Notably, although the prevalence rate of other mental illnesses such as depression and anxiety varied considerably by region of the world and nation, the prevalence rates of schizophrenia and bipolar disorder did not vary as much by region, suggesting socioeconomic, cultural, demographic and other factors that vary around the world have little impact on the prevalence of serious mental illness.
DALYs & YLDs
Mental illnesses were the 13th leading cause of disability-adjusted life years (DALYs) globally in 1990, growing to seventh by 2019, according to the results. Mental illnesses were the second leading cause of years lived with a disability (YLDs) across the world in both 1990 and 2019. Schizophrenia ranked third in both DALYs and YLDs of mental disorders across all ages, after depression and anxiety disorders.
“Schizophrenia impacted a smaller proportion of the global population than depressive and anxiety disorders, but the disability weight for an acute state of psychosis was the highest estimated across the GBD study,” the authors write. “The persistently high prevalence of these disorders, in addition to bipolar disorder and eating disorders, is especially concerning, because they not only impair health in their own right, but also increase the risk of other health outcomes, such as suicide (rated as the 18th leading cause of mortality in GBD 2019).”
Therefore, although serious mental illnesses are not as prevalent as other forms of mental health conditions, they have an increased disease burden on individuals due to how disabling the symptoms of the illnesses can be. Although the YLLs for schizophrenia and bipolar disorder were not able to be determined within the results of this study, the authors suggest that the potential years of life lost due to schizophrenia and bipolar disorder is especially concerning considering the other health risks associated with these disorders, including suicide.
Mental health & COVID-19
The results of this study were conducted prior to the COVID-19 pandemic, which has exacerbated mental health issues throughout the world. Epidemiological research suggests that the impact of the pandemic, both the direct psychological and biological and the long-term impacts on economic and social circumstances, may increase the prevalence of mental disorders across the globe. The authors suggest that mental illness already imposed a large burden before the COVID-19 pandemic and that the results “serve as a stark reminder for countries to re-evaluate their mental health service response more broadly.”
References
