ics. For example, the Australian findings that showed an increased history of ulcer were confirmed by supplemental data on the use of cimetidine, and a possible increase in the prevalence of arthritis was suggested by increased use of analgesics.
Second, further analyses of the examination data could be undertaken to broaden the preliminary results presented in this report. For example, evidence was presented comparing the examination diagnosis of posttraumatic stress disorder (PTSD) with the Structured Clinical Interview for DSM-III-R (SCID) and the Mississippi scale diagnoses. Data are available for item-by-item analyses of the SCID and Mississippi questionnaires to determine which items are most strongly correlated with the clinical diagnosis of PTSD. Also of interest would be a comparison of lifetime and current PTSD prevalences, given that there was little difference between the two physician-based estimates and a sizable difference for the SCID. Because a diagnosis of PTSD is based on the meeting of four criteria, an examination of changes over time in criterion scores could provide an unparalleled opportunity to study the natural history of PTSD over several decades. In addition, those subjects who met some but not all criteria (''partial PTSD'') could be profitably studied. Along more strictly methodological lines, a sample of the examinations could be reassessed by an outside panel to estimate interexaminer or even interhospital variability in the diagnosis of PTSD.
The psychological data from several sources might also be profitably compared and combined to gain more insight into psychiatric illnesses. A comparison of PTSD and depressive symptoms, for example, would provide important data on the comorbidity, or joint occurrence, of these two diagnoses. For another example, a discriminant analysis might be done, using all the psychiatric data, to compare POWs versus controls or even one POW group with another. Such an analysis could help determine which psychiatric scales or items distinguish subjects with PTSD from those without it by studying these relationships in one random half-sample and validating them in the other. It should also be noted that analyses like those of Chapter 6, which link examination conditions and prison camp treatment, did not include any demographic factors, although such an addition could provide further useful information. Similar analyses (with or without demographic factors) could be done using the SCID and questionnaire-derived measures of psychiatric illness.
Third, perhaps the most potentially fruitful area of secondary analysis (i.e., that would not require the collection of additional data) involves the linkage of previously and currently collected data. For example, the 1984–1985 questionnaire survey included the Center for Epidemiologic Studies depression (CES-D) scale, thus making it possible to compare 1984–1985 CES-D scores with current scores. Because the course of depressive symptoms is known to vary, this kind of test-retest analysis should provide useful