THE DST IN NORMAL CONTROL SUBJECTS 1550 Am J Psychiatry 141:12, December 1984 dumping ground. Psychiatr Q 50:191-201, 1978 11. Baxter E, Hopper K: The new mendicancy: homeless in New York City. Am J Orthopsychiatry 52:393-408, 1982 12. Crystal S, Goldstein M: New Arrivals: First-Time Shelter Cli- ents. New York, Human Resources Administration, 1983 13. Segal 5, Baumohl J: Engaging the disengaged: proposals on madness and vagrancy. Social Work 25:358-365, 1980 14. Phoenix South Community Mental Health Center and St Vin- cent Dc Paul Society: The Homeless of Phoenix: Who Are They and What Should Be Done? Phoenix, Ariz, Phoenix South Community Mental Health Center, 1983 is. Segal 5, Baumohl J, Johnson E: Falling through the cracks: mental disorder and social margin in a young vagrant popula- tion. Social Problems 24:387-400, 1977 16. Pepper B, Kirshner M, Ryglewicz H: The young adult chronic patient: overview of a population. Hosp Community Psychiatry 32:463-469, 1981 17. Sheets 5, Prevost J, Reihman J: Young adult chronic patients: three hypothesized subgroups. Hosp Community Psychiatry 33:197-203, 1982 The Dexamethasone Suppression Test in Normal Control Subjects: Comparison of Two Assays and Effect of Age Alan H. Rosenbaum, M.D., Alan F. Schatzberg, M.D., Robert A. MacLaughlin, M.S., Karen Snyder, Nai-Siang Jiang, Ph.D., Duane Ilstrup, M.S., Anthony J. Rothschild, M.D., and Bernard Kliman, M.D. The authors used competitive protein binding assay and radioimmunoassay to measure cortisol levels in 38 normal control subjects three times before and three times after administration of 1 mg of dexamethasone. They found significant interassay differences at I 1 :00 p.m. before dexamethasone and at all three postdexamethasone times. Analysis of variance revealed significant overall positive relationships between age and cortisol levels measured by both techniques. Age correlated significantly with postdexamethasone cortisol levels measured by radioimmunoassay but not when measured by competitive protein binding assay. Clinicians should obtain data from their laboratories as to appropriate cutoffs for cortisol suppression on the specific assay used. (Am J Psychiatry 141:1550-1555, 1984) Received Feb. 17, 1983; revised Aug. 3 and Oct. 31, 1983; accepted Jan. 11, 1984. From Henry Ford Hospital, Detroit; McLean Hospital, Belmont, Mass., Massachusetts General Hospital, Boston; and the Mayo Clinic, Rochester, Minn. Address reprint requests to Dr. Rosenbaum, 21415 Civic Center Dr., Suite 117, Southfield, MI 48076. The authors thank Gary Zammit for his assistance in the data analyses and Lynnal Williams and Barbara Klinger for the prepara- tion of the manuscript. Copyright 1984 American Psychiatric Association. I n recent years considerable attention has been paid to applying the dexamethasone suppression test (DST) to the diagnosis of patients with endogenous depression or melancholia. Results from a number of laboratories have indicated that a significant portion of patients with endogenous depression fail to suppress their cortisol production when challenged with a test dose of dexamethasone (1-8). Patients with schizo- phrenia, neurotic depression, and alcoholism (3 weeks after withdrawal) show a relatively tow incidence of nonsuppression after dexamethasone administration (2, 6, 8-10). However, the issues of specificity and the significance of test results have by no means been settled, since at least one investigator has failed to find significant differences between nonhospitatized pa- tients and normal controls (11 ). In addition, a recent report from another laboratory has indicated a rela- tivety high incidence of nonsuppression in manic pa- tients (P.E. Stokes, P.M. Stoll, S. Koslow, et at., “Pre- treatment Hypothalamic Pituitary-Adrenal Cortical Function in Affective Disease,” unpublished paper, 1982), and there has been some suggestion that elderly depressed patients have a higher incidence of non- suppression than do younger depressed patients (12, 13). This paper addresses three important questions re- garding the use of the DST in routine clinical practice: What is the incidence of nonsuppression in normal control subjects? What is the relationship of age to