The emerging fields of social epidemiology and population health seek to understand the social determinants of health. Especially, with regards to how income inequality causes health disparities, attention has been focused on material and psychosocial mechanisms. I use examples from the epidemiological and social science literature to argue for a third broad etiological framework: the role played by the ways we generally recognize, define, name, and categorize disease states and attribute them to a cause or set of causes. These framing effects shape population health by influencing: health and illness beliefs; patterns of consumption and other behaviors; perceptions of what interventions and policies work; class, ethnic, and other social dynamics; and clinical and public health practices. Important characteristics of many framing phenomena are their capacity to be self-perpetuating and their performative power. A better understanding of framing effects can lead to deploying them more deliberatively and flexibly to improve individual and population health.