Biological correlates of the Newcastle Scale in depressive illness: a multivariate approach.

Rapid eye movement latency (RL), delta max thyroid-stimulating hormone (dmTSH) and 1600 (DST16) and 2300 (DST23) post-dexamethasone cortisol values were determined in a group of 93 depressed patients who were assessed with the Newcastle Endogenous Depression Diagnostic Index (NEDDI). After the effects of age, gender and severity of illness were controlled for, stepwise multiple regression showed that depressive psychomotor activity and weight loss were the 2 NEDDI items most contributing to explain DST23 variance, as was depressive psychomotor activity for dmTSH variance. When the depressive sample was dichotomized according to the presence of these 2 items, the 2 groups had significantly different DST16, DST23, dmTSH and RL values. This suggests that weight loss, agitation and retardation could represent a core feature of a biologically mediated depressive subtype.