Edward Shorter, PhD, FRSC1; Herman M van Praag, MD, PhD2 Can J Psychiatry. 2010;55(2):59-64. The Argument for Disease It is chimerical to think that psychiatric illness can be collapsed into couple of smooth dimensions. This is conceit that comes to us from psychoanalysis, which was uninterested in specificity of treatment. In reality, just as there are discrete diseases of the kidney, there are discrete diseases of the brain that produce behavioural symptoms. These can no more be scaled than renal tuberculosis and renal carcinoma can be arrayed onto single dimension. Let us consider the view, articulated by Samuel Guze1 in 1992, that psychiatry is branch of medicine. If we are to regard psychiatric diagnoses as medical diagnoses, how might they be constructed? Building on Guze,1 Max Fink and Michael Alan Taylor2 have proposed 3-fold basis for carving out discrete psychiatric illnesses: describing an illness entity in well-circumscribed Psychopathologie terms; verifying its existence with laboratory measures; and, validating it with distinctive response to treatment. Based on this triune measure of what one might call disease-ness, what solid disease diagnoses does psychiatry possess? Melancholia Out of the soup of depression, it is possible to fish several solid diagnoses that fulfill the above criteria. The major depression of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III) is nondisease and should be divided into melancholia and nonmelancholia.3 Nonmelancholia is anything but discrete disease entity, while melancholia is probably the most solid disease that psychiatry possesses, characterized, in psychopathological terms, by psychomotor change and profound neurovegetative disturbances, and verified by such biological markers as positive response to the dexamethasone suppression test (in contrast to nonmelancholia), by REM latency, and by blunted thyroid-stimulating hormone response to exogenous thyrotropin-releasing hormone.4 Finally, melancholia is validated by distinctive response to tricyclic antidepressants (TCAs) and to electroconvulsive therapy (ECT). Not all patients with purported melancholia will display these biological markers, but it is profoundly interesting that within the melancholia diagnosis there is psychopathological core of patients possessing this biological homogeneity. (Atypical depression neither shows the typical neurovegetative signs of melancholia nor responds well to ECT.) These cases of melancholia cannot be arrayed on dimensional scale, except in the trivial sense that the disease waxes and wanes. Catatonia Formerly, catatonia was considered subtype of schizophrenia. DSM-IV conceded that features5' p 417 might characterize mood disorder as well. Seldom has catatonia been seen as an independent illness entity worthy of a home of its own, as Fink and Taylor6 put it (in the title of their article). Nevertheless, clearly it belongs on the list of genuine psychiatric diseases because its psychopathology is well specified and has rating scale of its own. To be sure, it does not possess biological marker (verification), but in intravenous lorazepam, catatonia possesses differential treatment response (validation). (No other psychotic illness responds to lorazepam; symptoms of catatonia are also relieved with ECT.) Catatonia has no dimensional features: the diagnosis is made with the presence of 2 or more signs, and the score on the catatonia rating scale does not influence the response to treatment. It would be incorrect to say, as the dimensional argument might put it, that all of us possess embryonic catatonic symptoms that then aggravate under stress. Atypical Depression Atypical depression is less clearly delineated than melancholia and catatonia, in psychopathological terms, but nonetheless displays some underlying biological unity. …