1. Department of Psychiatry and Human Behavior, Brown Medical School, Providence, RI
2. Sleep and Chronophysiology Laboratory, Department of Psychiatry, University of Michigan, Ann Arbor, MI
3. Health Services Research and Development Service, Veterans Affairs San Diego Healthcare System, Department of Psychiatry, University of California at San Diego, San Diego, CA
4. Centers for Behavioral and Preventive Medicine, Miriam Hospital, Providence, RI