Estimating the burden of common mental disorders attributable to lifestyle factors: Protocol for the Global burden of disease Lifestyle And mental Disorder (GLAD) Project

Background The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides critical evidence that guides local, regional, and global public health decisions. A key feature of the GBD is the collection and calculation of risk-outcome data for modifiable lifestyle exposures (e.g. dietary intake) and physical health outcomes (e.g. cancers). Despite evidence showing the contributions of these same lifestyle exposures to common mental disorders (CMDs), such as depression and anxiety, the GBD does not currently generate these lifestyle exposure-CMD outcome pairings. This gap is due to a lack of uniformly collected and analysed data about these exposures as they relate to CMDs. Such data are required to quantify whether, and to what degree, the global burden of CMDs could be reduced by targeting lifestyle factors at regional and global levels. We have established the Global burden of disease Lifestyle And mental Disorder (GLAD) Taskforce to address this gap. Our primary aim is to generate the necessary estimates to afford inclusion of lifestyle exposures as risk factors for CMDs in future GBD studies, initially focusing on the relationship between dietary intake and CMDs. Methods The GLAD Project is a multi-centre, collaborative effort to integrate lifestyle exposures as risk factors for CMDs in the GBD study. To achieve this aim, global epidemiological studies will be recruited to conduct harmonised data analyses estimating the risk, odds or hazards of lifestyle exposures with CMD outcomes. Initially, these models will focus on the relationship between dietary intake, as defined by the GBD and anxiety and depression. Results from individual member studies will then be meta-analysed and used to inform the GBD study. Discussion Our comprehensive, collaborative approach allows for concurrent execution of a harmonized statistical analysis protocol across multiple, internationally-renowned epidemiolgical cohorts. Consequently, given the worldwide influence of the GBD study, findings from the GLAD Project can offer valuable insights to policymakers around the globe around lifestyle-based mental health care. Registraton The GLAD Project and the following methods have been prospectively registered on Open Science Framework (https://doi.org/10.17605/OSF.IO/ZBG6X)