38 http://psy.psychiatryonline.org Psychosomatics 48:1, January-February 2007 Short-Term Stability of Diagnoses of Major and Minor Depression in Older Medical Inpatients MARTIN G. COLE, M.D., FRCP(C), JANE MCCUSKER, M.D., DR.P.H. CAROLE DUFOUIL,PH.D., ANTONIO CIAMPI,PH.D. ERIC BELZILE, M.SC. The authors sought to determine the short-term stability of diagnoses of major and minor depres- sion in older medical inpatients. The investigation was a test–retest design involving comparisons between different pairs of interviewers who assessed patients independently on medical wards of two acute-care, university-affiliated hospitals by use of the Diagnostic Interview Schedule (DIS) at intervals between 1 and 51 days. Patients were 380 cognitively-intact patients age 65, as- sessed twice with the DIS. Core depressive symptoms (depressed mood, loss of interest or plea- sure) were more stable than the other depressivesymptoms. The presence of moderate-to-severe depressive symptoms, moderate-to-severe disability, and depression symptoms of 6 months’ du- ration were associated with a higher short-term stability of diagnosis. Age, gender, language, education, rater, interval between assessments, baseline number of medications, medical comor- bidity, severity of medical illness, acute physiology score, and cognitive functioning were not as- sociated with short-term depression stability. Stability of diagnosis may be improved by emphasis on core depressive symptoms or the presence of more severe depressive symptoms, moderate-to- severe disability, and duration of symptoms 6 months. (Psychosomatics 2007; 48:38–45) Received August 24, 2005; revised November 30, 2005; accepted De- cember 5, 2005. From the Dept. of Psychiatry, St. Mary’s Hospital, and McGill Univ., Montreal, Que ´bec, Canada. Send correspondence and re- print requests to Martin G. Cole, M.D., FRCPC, Dept. of Psychiatry, St. Mary’s Hospital, 3830 Lacombe Avenue, Montreal, Que ´bec, Canada H3T 1M5. e-mail: martin.cole@ssss.gouv.qc.ca  2007 The Academy of Psychosomatic Medicine R eliability of psychiatric diagnosis refers to the extent to which independent diagnostic assessments yield the same results. 1 Usually, estimates of reliability are based on comparisons of diagnoses made by two or more raters at a single interview or at separate interviews a few days apart. Four sources of variation may affect the reliability of psy- chiatric diagnoses: 1) variation in the interviewer’s style; 2) variation in the patient’s story; 3) variation in diagnostic criteria; and 4) true changes in the patient’s symptoms over time. Important components of reliability include interrater reliability (IRR) and test–retest reliability (or short-term stability). 2 For years, achieving adequate IRR of psychiatric di- agnoses was considered to be a hopeless undertaking. Then in the 1960s and 1970s, studies demonstrated that good IRR could be achieved in younger, physically healthy adults by use of specially trained interviewers, standard- ized interview schedules, and explicit diagnostic criteria. 3–6 In univariate analysis, patients’ age and language, duration of symptoms, presence of mild cases, and interviewers’ experience were reported to affect levels of IRR. 7 Nonetheless, the short-term stability of diagnoses of depressive disorders in older medical inpatients remains a thorny clinical problem. As in younger adults, levels of depressive symptoms may change over time, even during the course of one episode, resulting in a striking number of changes in diagnoses. 8,9 Also, many of the symptoms of