Mental disorders as risk factors: assessing the evidence for the Global Burden of Disease Study

Mental disorders are associated with a considerable burden of disease as well as being risk factors for other health outcomes. The new Global Burden of Disease (GBD) Study will make estimates for both the disability and mortality directly associated with mental disorders, as well as the burden attributable to other health outcomes. Herein we discuss the process by which health outcomes in which mental disorders are risk factors are selected for inclusion in the GBD Study. We make suggestions for future research to strengthen the body of evidence for mental disorders as risk factors. We identified a list of potential associations between mental disorders and subsequent health outcomes based on a review of the literature and consultation with mental health experts. A two-stage filter was applied to identify mental disorders and health outcomes that meet the criteria for inclusion in the GBD Study. Major limitations in the current literature are discussed and illustrated with examples identified during our review. Only two associations are included in the new GBD Study. These associations are the increased risk of ischemic heart disease with major depression and mental disorders as a risk factor for suicide. There is evidence that mental disorders are independent risk factors for cardiovascular disease (CVD), type 2 diabetes and injuries. However, these associations were unable to be included because of insufficient data. The most common reasons for exclusion were inconsistent identification of 'cases', uncertain validity of health outcomes, lack of generalizability, insufficient control for confounding factors and lack of evidence for temporality. CVD, type 2 diabetes and injury are important public health policy areas. Prospective community studies of outcomes in patients with mental disorders are required, and their design must address a range of confounding factors.