1. Section of Medical Statistics and Epidemiology (M.C.M., C.M.), Department of Health Sciences, University of Pavia, 27100 Pavia, Italy
2. Departments of Biostatistics (M.C.M., D.A.G.), Columbia University, New York, New York 10032
3. Division of Statistical Genetics (M.C.M., D.A.G.), Columbia University, New York, New York 10032
4. National Disease Research Interchange (J.T.L., R.M., E.S.), Philadelphia, Pennsylvania 19103
5. New York State Psychiatric Institute (D.A.G.), New York, New York 10032
6. Departments of Psychiatry (D.A.G.), Columbia University, New York, New York 10032