What Makes a Mental Disorder Mental?

What makes a medical disorder mental rather than (exclusively) somatic or physical? Psychiatry to some extent depends for its existence as a medical specialty on the distinction between mental and somatic disorders, yet the history of this distinction presents a bewildering array of puzzling judgments, radical shifts, and seemingly arbitrary distinctions. The historical observation that putative mental disorders are often reclassified as physical disorders as soon as their physiologic basis is understood further confuses matters. Moreover, recent debates about such classifications often seem to reflect desires to protect professional turf or obtain optimal reimbursement for treatment more than they do the application of a coherent conceptual distinction. No wonder that Brülde and Radovic (2006) disarmingly admit at the outset of their exploration of this question that there is a case to be made that their topic is relatively unimportant or even meaningless intellectually, a rare way to start an inquiry!

Could there nonetheless be a cogent conceptual distinction lurking here? Brülde and Radovic usefully invite us to reframe the question, in effect as follows: Suppose we pay attention to professional and lay judgments as evidence but at the same time try to avoid being ensnared by the distortions resulting from turf issues and other pragmatic motives and constraints. Can we then identify some principled distinction in this domain that is worth making and that interestingly corresponds to the distinction generally made between mental disorders and strictly somatic disorders? Brülde and Radovic do not come to any confident or compelling conclusion about this.

My answer, based on my harmful dysfunction analysis of disorder (Wakefield, 1992a, 1992b, 1999a, 1999b), is that a mental disorder is a harmful mental dysfunction, where a mental dysfunction is a failure of the capacity of some mental mechanism to perform a function for which it was biologically designed. I argue that, owing to a series of logical missteps, Brülde and Radovic needlessly reject this view. After some preliminary comments and clarifications, I defend the internal dysfunction approach from the objections posed by Brülde and Radovic, and then conclude by elaborating this view in some new ways. Note that Brülde and Radovic critique something they call the "internal cause view" of what makes a disorder mental, and they name others who hold that view. However, my work figures prominently in their discussion, and for expository simplicity, I will presume to simply construe their arguments as aimed at the harmful dysfunction analysis.

Clarifying the Question

It is easy to misconstrue the question "What makes a mental disorder mental" as demanding a precise account of the mental, an error to which Brülde and Radovic succumb in their repeated complaints that various writers do not present principled accounts of the mental but rely on lists of prototypical mental states or tentative guidelines to fix the reference of mental. We would need a precise definition of mental if the problem were how to classify cases in which it is ambiguous whether some phenomenon is mental or physical. We might imagine, for example, someone being genuinely puzzled as to whether inability to sleep is failure of a mental function or process. But this sort of puzzle about the boundaries of the mental is not the problem with which Brülde and Radovic are concerned; anyway, ambiguous cases may just be inherently ambiguous. The problem, which a crisp definition of mental will not resolve, is what relation mental states or mechanisms must have to a disorder to make it a mental disorder; must there be mental symptoms, or mental dysfunctions, or either one, and so on? But, even if a precise resolution of the nature of the mental is not needed, some notion of the mental domain is essential in pursuing this discussion. We can pick out the mental ostensively, by pointing to lots of examples (e.g., perception, motivation, emotion, thought, and sensation) much more confidently than we can define it in a principled way. But because Brülde and Radovic find fault in such ostensive reference fixing, let me...