Acknowledgment: Collaborating NCS-R investigators include Ronald C. Kessler, PhD (principal investigator), Harvard Medical School, Boston, Mass; Kathleen Merikangas, PhD (co-principal investigator), NIMH, Bethesda, Md; James Anthony, MSc, PhD (Michigan State University, Lansing), William Eaton, PhD (The Johns Hopkins University, Baltimore, Md), Meyer Glantz, PhD (NIDA, Bethesda); Doreen Koretz, PhD (Harvard University, Cambridge, Mass), Jane McLeod, PhD (Indiana University, Indianapolis), Mark Olfson, MD, MPH (Columbia University College of Physicians and Surgeons, New York, NY), Harold Pincus, MD (University of Pittsburgh, Pittsburgh, Pa), Gregory E. Simon, MD, MPH (Group Health Cooperative, Seattle, Wash), Michael Von Korff, ScD (Group Health Cooperative, Seattle), Philip Wang, MD, DrPH (Harvard Medical School), Kenneth Wells, MD, MPH (University of California, Los Angeles), Elaine Wethington, PhD, DrPH (Cornell University, Ithaca, NY), and Hans-Ulrich Wittchen (Max Planck Institute of Psychiatry, Munich, Germany). A complete list of NCS publications and the full text of all NCS-R instruments can be found at http://www.hcp.med.harvard.edu/ncs. The NCS-R is carried out in conjunction with the World Health Organization World Mental Health (WMH) Survey Initiative. We thank the staff of the WMH Data Collection and Data Analysis Coordination Centres for assistance with instrumentation, fieldwork, and consultation on data analysis. A complete list of WMH publications can be found at http://www.hcp.med.harvard.edu/wmhcidi.