Richard Skolnik, lecturer for Yale's Essentials of Global Health course, devotes this session to mental illness as a global health burden. He covers the scope and scale of common conditions such as depression and anxiety disorders, how they are measured in terms of disability and mortality, and the risk factors and social determinants that shape who is most affected. The lecture follows the course's standard framework, examining the condition itself, its burden of disease, who bears that burden, and what cost-effective interventions exist to address it in low and middle income settings. As lecture 28 in the series, it applies the same analytical approach used earlier for communicable and noncommunicable diseases to psychiatric conditions, treating mental health as a core global health priority rather than a peripheral concern.