The authors express their gratitude to their colleagues whose tireless efforts have led to the donation of postmortem tissue to advance these studies: the Office of the Chief Medical Examiner of the District of Columbia, the Office of the Chief Medical Examiner for Northern Virginia (Fairfax), the Office of the Chief Medical Examiner of the State of Maryland (Baltimore), the Office of the Chief Medical Examiner for Kalamazoo County (Kalamazoo, Mich.), the University of North Dakota School of Medicine Department of Pathology, Forensic Pathology Center (Grand Forks), and the Santa Clara County Office of the Chief Medical Examiner (San Jose, Calif.). This work was supported with resources and use of facilities at the VA Connecticut Health Care System, West Haven; the Central Texas Veterans Health Care System, Temple, Tex.; the Durham VA Healthcare System, Durham, N.C.; the VA San Diego Healthcare System, La Jolla, Calif.; the VA Boston Healthcare System, Boston; and the National Center for PTSD, U.S. Department of Veterans Affairs. The authors acknowledge the contributions of Amy Deep-Soboslay and Llewellyn B. Bigelow, M.D., for their diagnostic expertise and Dr. Daniel R. Weinberger for providing constructive commentary and editing of the manuscript. Finally, the authors are indebted to the generosity of the families of the decedents, who donated the brain tissue used in these studies.