The usefulness of Wakefield's definition for the diagnostic manuals

No one has done more in the last decade or so to clarify and analyse the concept of mental disorder than Jerome Wakefield, and it is timely to consider his work during preparations for new editions of the DSM and the ICD. These will involve review of the reliability of diagnoses, and the various issues of validity of classification of symptoms into syndromes, and syndromes into higher-order categories.

The further and distinctive kind of validity to which Wakefield has consistently drawn attention since his first papers in the early 1990s is what he has called the problem of conceptual validity: to what extent do the manuals capture all and only the mental disorders (or mental and behavioural disorders), and to what extent have they left some out, or, most discussed, to what extent have they mistakenly included some non-disorders in. This is the "overinclusiveness" or "false positive" problem. The diagnostic criteria for some disorders are too lax, in the sense that particular presentations may satisfy them, but are - apparently - not cases of disorder. Wakefield has argued along these lines for many conditions, including major depressive disorder, conduct disorder and social phobia.

Wakefield has consistently linked the problem of conceptual validity of diagnosing disorder - are we really diagnosing disorder? - to the fundamental problem of reliability of diagnosis. Following Hempel's advice, the diagnostic manuals have sought to make symptom description as purely observational as possible, without speculations as to aetiology, and then (especially in the DSM) to have syndrome composition as arithmetically algorithmic as possible (symptom counts of more or less complicated kinds). Wakefield's argument has been that this methodology in effect detaches troublesome mental states and behaviours from their context, failing to take account of whether they are "normal" responses to adversities, or arise in understandable ways according to normal learning - as opposed to genuine disorders involving dysfunction.

So can Wakefield's analysis help sort out what are the "genuine disorders"? In brief form the analysis is: mental disorder = harmful dysfunction. This brief form is trivial - inasmuch as it substitutes "dysfunction" for "disorder" - and should not be mistaken for the non-trivial full version, which is (along the lines of): mental disorder = harmful failure of a natural mental or behavioural mechanism to function as designed in evolution. Can this help solve the problem of conceptual validity for the psychiatric manuals? Can it be used to make particular diagnostic criteria sets more valid, by excluding non-disordered conditions?

It may be that Wakefield's analysis of "mental disorder" is conceptually correct. I have argued elsewhere that it is not (1), but the issues are too long for here. It is fair to say in any case that no one has come up with such a rigorous definition that is better. So should it be put in the preambles to the DSM-V and ICD-11?

The problem here would be the fairly obvious one - signalled by Wakefield's own arguments - namely, that reliability would be seriously jeopardised. To establish that a condition is a disorder in the sense of Wakefield's analysis, we would have to establish, or at least have a consensus about, whether it arose because of or at least involved "failure of a natural mental or behavioural mechanism to function as designed in evolution". But as opposed to what? Behavioural scientists working in an evolutionary theoretic framework have suggested that failure of function in Wakefield's sense as a pathway to harmful conditions can be contrasted with, for instance, evolutionary design/current environment mismatch, or maladaptive learning (2,3). If these are the kinds of intended contrasts, we need to wait until the science has been done to establish which types or sub-types of problems are "genuine disorders" in the sense of Wakefield's analysis, and which are not. And in the meantime, during what might be a long wait, we would need another name for the problems, not disorder (which in this scenario we are interpreting in Wakefield's sense), but perhaps, for instance, mental health problems, the criteria for which would have to be reliable enough for us to do meaningful, generalizable research. We would be back where we are with (another) change of name.

If we were to follow this tack we may eventually sort out what conditions or sub-types are "disorders" (in the sense required by Wakefield's evolutionary theoretic analysis) and which are not. The ones that are not - Wakefield concedes - may still be associated with harm and with risk of harm. They would therefore still be in need of treatment (in a general sense including watchful waiting). Indeed the harm or risk associated with the non-disorder variants may be as high as for the "genuine disorders" - we won't know this until the science has been done (it cannot be known from the armchair). We would have a manual of "mental disorders and related mental health problems" (somewhat like the relaxed full title of the ICD) in which the difference between the two is less important than the associated harm and risk and consequent need for clinical attention and research. The evolutionary theoretic definition would not have done much practical work, because actually what drives practice is harm and risk.