To improve the health outcomes of people with mental, neurological, and substance use disorders in both HICs and LMICs, it is important to understand not only the number and distribution of these disorders among countries, but also how they impact on health in terms of both mortality and disability, compared with other diseases and injuries. The first Global Burden of Disease Study (GBD 1990), which published data on disease burden in 1990 [9], reported that the category of mental, neurological, and substance use disorders—a grouping that included depression, selected anxiety disorders, bipolar disorder, schizophrenia, epilepsy, dementia, Parkinson’s disease, multiple sclerosis, alcohol, and drug use disorders—accounted for a significant proportion of the world’s disease burden, as measured by disability-adjusted life years (DALYs). The DALY is a health metric that captures the non-fatal component of the disease burden as years live with disability (YLDs), and the fatal component as years lost to premature mortality (YLLs) [9].
