Changes in diagnostic case mix in psychiatric care in general hospitals, 1980-85

The Hospital Discharge Survey of 1980 and 1985 was used to assess changes in diagnostic case mix of psychiatric inpatient care in short-term, nonfederal general hospitals. Information regarding presence of psychiatric and chemical dependency units was added to both surveys, and information regarding exemption from Medicare's PPS system was noted for 1985. The largest increase was in ICD-9 code 296 (affective disorder), which more than doubled in frequency, along with a similar decrease in Diagnosis-Related Group 426, depressive neurosis. One explanation for this sizable shift was "gaming the system." One cannot conclusively, however, distinguish between gaming the system and the effects of changing professional views of depression during this time period. Other variables potentially contributing to the effect are described as well.