Dexamethasone suppression test and TRH-TSH test in subaffective dysthymia and character-spectrum disorder.

Based on Akiskal's criteria of subaffective dysthymia (SDT) and character-spectrum disorder (CSD) as the two, etiologically distinct forms of early-onset primary dysthymia, the authors investigated the dexamethasone suppression test (DST) in 18 patients with SDT and in 30 patients with CSD. TRH-TSH test was also investigated in smaller subsamples of the patients (n = 8, and n = 7, respectively). Fifty percent of the patients with SDT showed abnormal DST and TRH-TSH test results respectively, while the figures in the CSD patients were 7% and 0%. These findings suggest that SDT is a clinically diagnosable and biologically distinct subgroup within the broader category of early-onset primary dysthymia, which represents a symptomatically milder version of primary affective disorder.