Data gaps in prevalence rates of mental health conditions around the world: a retrospective analysis of nationally representative data.

BACKGROUND Mental health conditions contribute substantially to the global burden of disease, affecting quality of life and leading to increased health-care expenses and mortality. Accurate data on the prevalence and correlates of these disorders are crucial for policy making, advocacy, and improving population health, but there are notable gaps in the available data on the magnitude of mental health difficulties around the world. This study aims to identify and quantify the data gaps on mental disorders across the lifespan in the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021. METHODS We analysed the nationally representative data sources used by GBD 2021 on 11 mental health conditions, including neurodevelopmental disorders and neurodivergence, general psychiatric disorders, and substance-use disorders. Our analysis focused on the geographical origin of the data sources, the age groups and mental health conditions or neurodivergence covered, and temporal trends on the scientific production of data. FINDINGS GBD 2021 identified 1241 unique nationally representative data sources for mental health conditions since 1950. Neurodevelopmental disorders and neurodivergence had the least coverage, with less than 13% of countries having prevalence data. Low-income countries had the largest data gap, with no data on neurodevelopmental disorders and neurodivergence, only 29% with any data on general psychiatric disorders, and 21% with data on substance-use disorders. The African and Western Pacific regions had the largest data gaps, and children were the least covered demographic: almost 90% of countries did not have any data for children. Most data (70-80% across disorders) were obtained before 2010. INTERPRETATION Substantial gaps in prevalence data persist globally, particularly in children and in low-income countries. Despite increased scientific production in the 2000s, most mental disorders remain under-represented. Coordinated global efforts are required to enhance mental health data collection and address these gaps. FUNDING Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil.