1. Department of Psychiatry, University of Pittsburgh School of Medicine, 2Department of Psychology, University of Pittsburgh, Pittsburgh, PA 15260 3Department of Psychiatry and Human Behavior, Brown Medical School, Providence, RI 02903, 4School of Public Health, University of California, Berkeley, Berkeley, CA 94720 and 5Mood and Anxiety Disorders Program, National Institute of Mental Health, Bethesda, MD 20892 USA