Volume 38 · Number 12
DECEMBER 2008

Balancing Treatment Comparisons in Longitudinal Studies

By Sue M. Marcus, PhD; Juned Siddique, DrPH; Thomas R. Ten Have, PhD; Robert D. Gibbons, PhD; Elizabeth Stuart, PhD; Sharon-Lise T. Normand, PhD

Evaluation of treatment efficacy in psychiatric trials involves a comparison of outcomes for those who receive a treatment versus those who receive a control or comparison treatment. However, if the treatment and comparison groups are not comparable or “balanced,” observed differences in outcomes between treated and comparison groups may be due, in part, to these imbalances. In such settings, estimates of treatment efficacy may be biased unless some adjustments are made to make the groups more comparable.

ABOUT THE AUTHORS

Sue M. Marcus, PhD, is with the Department of Psychiatry, Mount Sinai School of Medicine, New York. Juned Siddique, DrPH, is with the Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, Chicago. Thomas R. Ten Have, PhD, is with the Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia. Robert D. Gibbons, PhD, is Professor of Biostatistics and Psychiatry, and is Director of the Center for Health Statistics, University of Illinois at Chicago. Elizabeth Stuart, PhD, is with the Johns Hopkins Bloomberg School of Public Health, Baltimore. Sharon-Lise T. Normand, PhD, is with the Department of Health Care Policy, Harvard Medical School, and the Department of Biostatistics, Harvard School of Public Health, Boston.

Address correspondence to Sue Marcus, PhD, Department of Psychiatry, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1230, New York, NY 10029; fax 212-860-4630; or e-mail sue.marcus@mssm.edu.

Dr. Marcus, Dr. Siddique, Dr. Ten Have, Dr. Gibbons, Dr. Stuart, and Dr. Normand, have disclosed no relevant financial relationships.