Dexamethasone suppression test in psychiatric diagnosis and psychopathology for Chinese patients

The rate of abnormal dexamethasone suppression test (AbDST, post-dexamethasone cortisol greater than 5.0 micrograms/dl) was analyzed in different psychiatric samples, diagnostic categories and different time points of blood sampling. Differences in the AbDST rate in different samples were largely due to different composition of diagnostic categories and time points of samplings. By standard DST protocol (using 4 PM and 11 PM as sampling time points), melancholics had the highest AbDST rate (58.5%) among all diagnostic groups. DST was not a practical technique for differential diagnosis in psychiatric practice because of low prevalence of melancholia in the total patient population. However, it could be a promising variable for psychopathological study. The rate of AbDST was higher at the sampling time of 4 PM than any others. For one time point sampling, the 4 PM one was suggested. 8 AM and 4 PM sampling times were suggested as a practical 2-time-point sampling for DST. The rate of AbDST in different diagnostic groups had a positive relation with the severity of depressive psychopathology in a global sense. There was not any single item or any cluster of depressive symptomatology consistently related to AbDST among all diagnostic categories. Each diagnostic category had its own specific depressive symptoms in relation to AbDST, either positively or negatively. The severity of hypothalamic-pituitary-adrenal axis dysfunction, as shown in persistent AbDST and a high level of post-dexamethasone cortisol level, showed heterogeneous relation with depressive psychopathology. The relation was positive in schizophrenia and mania, was nill in melancholia, and probably reversed U relation in other psychotics and neurotics. Multiple psychopathological and pathophysiological mechanisms responsible for AbDST were suggested.