The dexamethasone suppression test in schizophrenia.

In a study of 20 inpatients who met DSM-III criteria for schizophrenia, there was a high incidence of depressed mood (N = 14), DSM-III melancholia (N = 6) and dexamethasone nonsuppression (N = 7). This incidence of positive DSTs (serum cortisol greater than 5 micrograms/dl at 3:30 or 10:00) was significantly higher than the expected rate based on a literature review (35% vs. 4%, p less than .001). A positive DST did not result in all cases in antidepressant pharmacotherapy, nor did a negative result preclude such treatment. Hence, clinicians in the study did not "treat the DST" in the absence of clinical evidence of depression. This study is consistent with others reporting a significant proportion of depressed schizophrenics. However, some studies have claimed no differences in response to dexamethasone between nondepressed and schizophrenic patients. These findings do not support a biological basis for the RDC differentiation of primary and secondary depression and challenge the DSM-III concept of schizophrenia as excluding the diagnosis of major depression. Viewed from a different perspective, the data may support recent reports casting doubt on the specificity of the DST.