Introduction Psychiatric epidemiology uses population-based survey methods to inform understanding of the prevalence, course, and correlates of mental disorders. Whereas the focus of clinical practice is on the individual patient, psychiatric epidemiology studies the manifestation and distribution of mental disorders in the general population in order to evaluate the public health burden and economic impact of psychiatric conditions, and to provide clues to etiology. Over the past three decades, advances in psychiatric epidemiology and population-based sampling methodology have enhanced our understanding of the public health burden of psychiatric disorders. Measurement in epidemiology has progressed from reliance on unsystematic reports from hospitals and other service facilities to employment of highly structured interviews that reliably assess well-defined diagnostic entities in representative household samples (Dohrenwend & Dohrenwend 1982). In the United States, almost three decades ago the Epidemiological Catchment Area (ECA) study documented rates of DSM-III conditions in five US communities in household and institutional settings (Robins & Regier 1991). Since this landmark study, a number of largescale US surveys have expanded on the ECA findings to provide nationally representative data using broad structured diagnostic interviews that reflect evolving iterations of the DSM (e.g., Kessler et al. 1994, 2005a, Grant et al. 2004a).