A twin study of prenatal injury markers in psychosis: Timing the insult : H. Stefan Bracha, M.D., E. Fuller Torrey, M.D., Llewellyn B. Bigelow, M.D., Beverly Linington, M.A. Psychiatry and Neurology, University of Arkansas for Medical Sciences, and VAMC, 116A1/NLR, North Little Rock, AR 72114-1706