The independence of neurotic and endogenous depression

Statistics and the nature of depression

A critical examination is made of the role that statistical methods have played in the understanding of depression. The development of instruments for measuring depression is illustrated by reference to the Beck Depression Inventory and the Hamilton Rating Scale. The controversy over the existence of one or two types of depression is examined from the perspective of the statistical tools used. Some of the problems in studies of the heritability of depression are outlined. The development of clinical trials of depression is examined, with particular reference to ECT and maintenance therapy, and the role of meta-analysis is discussed.

Depression sub-typing: unitary, binary or arbitrary?

The strongest statistical support for the binary view of depression has been provided by factor (principal components) analytic studies which delineate a bipolar factor with features interpreted as reflecting "endogenous depression" and "neurotic depression" at opposing poles. We review the seminal studies to suggest instead that the bipolar factor has generally polarised depression and anxiety, and that no such entity or symptom complex of "neurotic depression" has been isolated. Instead "neurotic depression" has been defined principally by features of anxiety and personality style. We argue that the suggested entity is, in fact, a pseudo-entity, being no more than a residual group of non-depressive features without any significant intrinsic depressive characteristics. We support our interpretation by showing comparable solutions in published studies of depressives alone, contrasted with separate analyses of anxious and depressed patients. We also report two studies in which the "neurotic depressive" pole is made to appear and disappear by the inclusion and exclusion of anxiety items. As factor analytic studies have defined the "residual" pole so variably, we argue that some features held to distinguish neurotic depression are of no utility and that such a diagnosis is meaningless. We suggest that the clinician should not proceed (after excluding endogenous depression) to conclude that the default option is necessarily an entity "neurotic depression" and that instead a heterogeneous group of options (e.g. anxiety, personality disorder) require review. If the "neurotic depressive" type of the multivariate analytic studies is a pseudo-entity, then a modified unitary view of depression may be valid.

Endogenous depression as a construct: a quantitative analysis of the literature and a study of clinician judgements

We review the concept of endogenous depression historically and undertake quantitative analyses of representative factor analytic studies. We also report an empirical study, isolating symptoms and signs associated with a clinical diagnosis of psychotic/endogenous depression, made by a large number of clinical raters assessing 300 depressives. The quantitative analyses and the study of practising psychiatrists agreed in delineating depressive type and together suggest a more restricted construct of endogenous and psychotic depression than has been held historically. Key clinical features isolated were severity, retardation, delusions and paranoid features, non-reactivity and non-variability in mood, while vegetative features appeared to lack relevance.

Life stress and symptom pattern in out-patient depression

The relationship was examined between symptoms rated in a sample of out-patient depressives, and measures of life stress derived from a separate interview. There was an association between symptoms reflecting the endogenous-neurotic distinction and life stress. However, the association was relatively weak, and was mainly with total social problems at the time of presentation, rather than with life events at onset. These findings are consistent with other studies which indicate that the absence of prior life events and the presence of the endogenous symptom pattern are only weakly related.

The Newcastle Endogenous Depression Diagnostic Index: validity and reliability

The newcastle Endogenous Depression Diagnostic Index of Carney et al. was studied for reliability and validity. Good inter-rater reliability was obtained for diagnostic category and for item scores in 36 patients. The scale showed construct validity with reference to the Hamilton and Montgomery-Asberg rating scales. Concurrent validity was shown relative to other diagnostic scales of endogenous depression. Predictive validity was demonstrated in that endogenous and nonendogenous depressive responded differently to isocarboxazid. The continued use of 5 as the point of separation between endogenous and nonendogenous depression is questionable.

Diagnosis of endogenous depression. Comparison of clinical, research and neuroendocrine criteria

Eighty-nine depressed outpatients were studied by clinical criteria, Research Diagnostic Criteria (RDC), and the dexamethasone suppression test (DST) of neuroendocrine regulation. A simple outpatient version of the DST, requiring only one blood sample, correctly identified 40% of patients diagnosed clinically as endogenous depression (ED), with a specificity of 98% and a diagnostic confidence of 95%. Differences in age, sex, or severity of symptoms between endogenous and non-endogenous depressives did not account for these results. By comparison, the diagnostic performance of the DST was weaker for the RDC categories Major Depressive Disorder (MDD) and primary MDD. These were less selective and more heterogeneous than the clinical category ED. The clinical diagnoses of ED were supported in 98% of cases by the RDC, but 22% of RDC endogenous MDD diagnoses were not supported by the clinical diagnoses. Abnormal DST results were found only in patients with both the clinical diagnosis of ED and the RDC diagnosis of endogenous MDD. Patients with definite endogenous MDD had a significantly higher frequency of abnormal DST results (42%) than those with probable endogenous MDD (14%), or those with other RDC diagnoses (3%). A significant association was found between positive DST results and a positive family history of depression. These results support other evidence for use of a positive DST result as an external validating criterion for ED. The category MDD contained all cases diagnosed clinically as ED, but was diluted by cases diagnosed clinically as non-endogenous depression who had no neuroendocrine disturbance. The results also confirmed that the endogenous/non-endogenous and primary/secondary classifications of depression are not identical. We conclude: (1) that the DST can be used in the differential diagnosis of depressed outpatients as well as inpatients; (2) that the RDC category primary MDD and the Washington University category primary depression are more heterogeneous and probably less valid than the clinical category ED; (3) that the RDC for endogenous MDD have only moderate validity; (4) that RDC diagnoses cannot substitute for careful clinical diagnoses in research studies; (5) that the best use of the RDC is to support clinical diagnoses, but not to generate diagnoses independently as a free-standing system; (6) that the concept of endogenous or endogenomorphic depression has validity and should be retained in research studies of depression.

Depression: a multivariate study of Sir Aubrey Lewis's data on melancholia

Principal component analyses were carried out on 51 items abstracted from Lewis's 1934 and 1936 papers. The first component was bipolar, differentiating between endogenous items and those that were mainly neurotic. The distributions of the first component scores by cluster indicated that there were two separate clusters of patients, one mainly endogenous, the other neurotic. It was concluded that Lewis's data indicate that there are at least two qualitatively different depressive illnesses. Further component analyses were carried out using the 25 endogenous items. The first component was a general one of endogenous depression. The distributions of its scores were bimodal, indicating that there were two groups of patients, those who suffered from endogenous depression and those who did not. These analyses indicated that endogenous depression is a categorical illness.

Observer variation and depressive phenomenology

An investigation into observer variation and depressive phenomenology is described. A group of 6 clinicians independently completed a 43-item sheet for 20 depressed patients at the same clinical interview. The coefficient of agreements on the items are given. Patient variables and observer variables did not have any influence on the degree of agreement. There was also an agreement in the subtyping of depression.

An evaluation of evidence on depressive classification and some alternative suggestions from physiology

The wealth of material on depressive classification provides both researcher and clinician with a sorting task of monumental proportions. Moreover the criticisms which have been fired at studies of depressive classification using symptoms as a data base, also require systematic sorting and elucidation. An attempt has been made to review the major studies of depressive classification in a systematic way, together with the principal criticisms which have been made of them. The survey is not exhaustive but aims at providing a relatively ordered overview of the area. The most critical issue, that of subjectivity of data collection is taken up, and it is suggested that biological measures may form a more objective data base for studies of depressive classification than ratings of symptoms and behaviour.

Depressive syndromes and the classification of patients

The scores of 269 depressed patients on the Depressive Category-Type Scale were analysed. The distributions of component and total scores were found to be bimodal, indicating that most depressed patients can be divided into an endogenous group and another characterized by the presence of neurotic features and the absence of endogenous ones. These findings were discussed in relation to those of other investigators. The relationship between the differentiation of syndromes and the classification of patients into corresponding diagnostic groups was considered. Finally, it was suggested that it should be interesting to try to estimate, from published data, the correlation between endogenous and neurotic depression in the general population.

Correlation of clinical features of depressed out-patients with response to amitriptyline and protriptyline

Considerable inconsistency exists in the literature concerning the clinical features of depression associated with a good response to anti-depressant medication. Abrahamet al. (1963) summarized the literature to that date; the general consensus of opinion was that imipramine had its best effect in depressions of the endogenous rather than those of the neurotic type, but their study on depressed out-patients did not support this conclusion. Browneet al. (1963), working with in-patients, reported that reactive depressives showed a better response to amitriptyline than did endogenous depressives. Burtet al. (1962), in their report of the response of 73 depressed female in-patients treated with imipramine or amitriptyline, demonstrated a much better response to both drugs by reactive as compared with endogenous depressives. Spearet al. (1964) found no significant difference in respect to “endogenicity”, in the response of depressed in- and out-patients to tranylcypromine and imipramine. Richmond and Roberts (1964) reported that out-patients suffering from endogenous depression responded much better to a variety of anti-depressant drugs than did those suffering from reactive depression.