Depressive disorders one two or three principal types

The extended debate as to whether the depressive disorders are best conceptualized as comprising one or more distinct disorders warrants overview. The 'unitarian' view posits one depressive disorder, varying essentially by severity. The strict 'binarian' view argues for two separate types.

Debate did not commence this century. Altschule(6) suggested that St Paul distinguished between two types of depression, one 'from God' and the other 'of the world' (Corinthians 7:10), and that several distinguished Christian leaders from the fifth to the eighth century recognized a distinction between 'rational' and 'irrational' depression. Jackson(7) has extensively detailed historic descriptions of melancholic depression from early Roman and Greek views through to the twentieth century, charting the key defining clinical features, with an early emphasis on observable signs—particularly of psychomotor disturbance. Similarly, Berrios (8) informs us that, in classical antiquity 'melancholia was defined in terms of overt behavioural features ... [and] that symptoms ... were not part of the concept'.

Rich descriptions of melancholia as a depressive condition marked by psychomotor retardation or agitation emerged in the late nineteenth century (e.g. Maudsley (9)), while Kraepelin*10) brought mania and melancholia together as manic-depressive insanity. Kraepelin defined a 'melancholia simplex' condition characterized by a key feature of psychic inhibition, causing paralysis of thought, memory difficulties, and a sense of weariness and enervation, but without psychotic features. He also defined a second melancholic group with delusions and hallucinations in addition to psychomotor retardation or stupor, as well as a third group of 'agitated melancholia' marked by distinct motor agitation. In 1917, Freud (H.> published his influential paper on melancholia, and Jackson argued that this changed the descriptive focus of melancholia in the twentieth century, with theorists and analysts then focusing on cognitive and intrapsychic features. Subsequently, and continuing still, clinical description of depression weighted symptoms, and minimized or ignored behavioural signs.

In the 1920s, Mapother(12> argued that it was pointless to distinguish between 'psychotic' and 'neurotic' forms of depression, as both lay along a continuum. This provocative paper, presenting the unitarian position, challenged diagnostic practice. The 'binarians' responded, with Gillespie (13) arguing for two types of depression: first, an 'autonomous' type (previously and subsequently termed 'endogenous depression'), which, once precipitated, tended to run an independent course and be unresponsive to the environment; second, a 'reactive' type, in which the depression was responsive to the environment (although earlier, the concept of 'reactivity' had been tied to onset induced by a psychogenic factor).

The debate was strongly influenced by Lewis's study of 61 patients. Lewis (14> concluded that he could find no clear demarcation between depressive types, examined both cross-sectionally and longitudinally, thus delivering support to the unitarian view. This view prevailed until the introduction of multivariate statistical approaches and computers led to the debate being reactivated in the 1960s, with the so-called Newcastle School arguing strongly that their analyses supported a binary view. In a representative paper, Kiloh and Garside (15,> used a factor-analytic strategy to argue for separate 'endogenous' and 'neurotic' depressive conditions. Factor analysis is not ideal for developing a typology, in that it produces dimensions (here symptoms) rather than groupings of patients. Subsequently, more appropriate strategies have been used, such as cluster analysis1,) and latent class analysis/17» and with those studies providing support for separate classes. Critics suggest, however, that such classes or subgroups could still be determined by severity or, even if subtypes can be identified, question whether subclassification is of any moment.

This latter challenge is fundamental, taking us to the heart of any consideration of the diagnosis and classification of the depressive disorders. To the unitarians (despite evidence of quite varying aetiological factors), depression essentially varies only by degree, allowing treatment decisions (e.g. electroconvulsive therapy (ECT), antidepressant drugs, psychotherapy, or cognitive-behavioural therapy) to be decided on the basis of severity or frequency of episode. The opposing argument—for conceding subtypes—has been well put by Kendell, (18) who drew on important historical analogies: distinguishing between cardiac and renal forms of 'dropsy' allowed prediction of those who would respond to digitalis, and it was only when 'the pox' had been identified as comprising smallpox and chickenpox that it was possible to predict who was likely to live or die.

Thus, if there are valid depressive subtypes, the contribution of putative psychosocial and biological risk factors may vary across each, so that the subtypes may have distinctly differing neurobiological determinants and may have differential response to the broad treatment modalities. If this is true, then to force homogeneity by creating dimensionally based categories such as 'major depression' is to ensure muddied results. This is not merely a theoretical objection, when, as noted by Hickie,(l9> large numbers of studies of patients with DSM-defined 'major depression' have failed to demonstrate any coherent pattern of neurobiological changes, replicate key biological correlates, and demonstrate any specific pattern of treatment response outside inpatient treatment settings.

How then have the official classificatory systems addressed such a substantive issue? In developing the DSM-III system, (20) the working group was required to make a decision on the competing unitarian or binarian models. While the binarians were at the door, they had, until then, failed to prove their case and the DSM-III committee chose a compromise. Thus, classification was predicated on an initial dimensional component (i.e. major versus minor disorders). If criteria for a major disorder were met, second-order and more categorical decisions about the presence of melancholia or psychotic depression were specified. This model proved unsatisfactory for melancholia. For example, Zimmerman and colleagues(21> noted that the DSM-III melancholia criteria set, unlike the definition provided in the predecessor (DSM-II), 'did not predict treatment response'. Thus, in DSM-IIIR(22) the criteria set for melancholia was revised to include complete recovery after previous episodes, previous good response to somatic treatments, and no significant personality disturbance, to overcome the lack of predictive validity by building into the definition some of the 'givens' held by many clinicians about melancholia. However, the criteria set for melancholia developed for DSM-IV returned essentially to the DSM-III set, with limitations which are considered below. The contrasting system, ICD-10, is essentially based on a dimensional or unitarian view of the depressive disorders.

Thus, there has been an extended debate as to whether a categorical and more 'biological' type of depression exists. There have been many ascriptions to this condition, variably termed 'endogenous', 'endogenomorphic', 'autonomous', and 'melancholic' depression. Definitions over time include a distinctive pattern of symptoms and signs, the greater relevance of genetic and other biological determinants, as contrasted with psychosocial precipitants (so leading to the term 'endogenous depression'), minimal response to placebo, and a selective response to antidepressant medication and ECT. There is evidence to support each of these propositions,(23) although the term 'endogenous' has proved unsatisfactory, as those with melancholia may commonly report antecedent life events. However, only the first issue falls within this chapter's purview, and will be addressed shortly.

Whether psychotic (or delusional) depression is a 'severe' form of melancholia or a separate entity also remains problematic. DSM-III had a category 'major depression with psychotic features' for use when delusions or hallucinations were present or when there was 'depressive stupor (the individual is mute and unresponsive)', thus viewing 'psychotic depression' as a subtype of the generic 'major depression' category rather than a subtype of melancholia. The practical advantage to that definition was in recognizing that psychomotor disturbance can be so severe that some patients will not volunteer or admit to psychotic features—which may only be confirmed by the patient after improvement. While 'depressive stupor' may then be a useful marker or proxy for the condition, this criterion was not retained in DSM-IIIR or DSM-IV, but is included in ICD-10. Two points argue for psychotic depression as a distinct entity: the presence of psychotic features, and its poor response to antidepressant medication alone or neuroleptic medication alone. (24)

A strict interpretation of the 'binary' view would place the non-psychotic and non-melancholic depressive conditions in a pure second class. Variably termed 'neurotic' or 'reactive' depression over time, this class is best regarded as a heterogeneous residue category (i.e. non-melancholic depression), with its heterogeneity expressed widely—across aetiological factors, clinical expression, and natural and treated history.

It is suggested here that there are three relatively separate depressive classes: psychotic, melancholic, and the non-melancholic disorders. Clinical differentiation of each will be described shortly.

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