[Quantitative psychopathology of depression: application of the Newcastle Scale]

Hypothalamo-pituitary axis disturbances, such as plasma cortisol escape after dexamethasone (DXM) administration or blunted TSH response to TRH, and sleep architecture abnormalities such as shortened REM latency are frequently encountered in depressive disorders. These anomalies only occur in a subgroup of depressed patients and could thus identify a biological or endogenous component to depressive illness. Several definitions of this endogenous depression have been proposed. In this regard, using biological criteria, the Newcastle scale remains the strongest validated clinical definition. In this study, 93 patients (58 women and 35 men) aged 15-79 years (mean: 42) who complained about a depressed mood were admitted for biological investigations (DXM and TRH tests, sleep EEG recording) after a drug wash-out period of at least 10 days. Patients were assessed with the Newcastle scale and diagnosed with RDC using the SADS. After the effects of age, gender and severity of illness were controlled for, multiple regression analyses showed that depressive pychomotor activity and weight loss were the 2 items of the Newcastle scale most contributing to explain the variances of the neuroendocrine tests results. Moreover, when the sample was dichotomized according to the presence of these 2 items, the 2 groups had significantly different post DXM cortisol values, TSH levels after TRH and REM latency values. The 2 groups (biological and non-biological) were then characterized using 16 depressive symptoms more frequently cited in 15 operational definitions of endogenous depression. A logistic regression analysis showed that weight loss, anhedonia, early awakening, and morning worsening of mood were the 4 symptoms that best distinguished biological from non-biological patients group. These symptoms could reflect biological abnormalities in depression and form the core of the endogenous depression.