We need science to be useful too
Authors: Derek Bolton
Journal: World Psychiatry (2016)

Jablensky's notion of a fundamental contrast between utility and validity in psychiatric classification1 probably bears a relation to the tensions between pragmatic and correspondence ideas of truth. Having both in play at once creates conundrums. Of particular relevance, if one supposes that truth is correspondence with reality as it really is, then mere pragmatic value – utility – will always look like it falls short. In several key places, Jablensky refers to the shifting nature of utility, contrasted with “reality”, understood in this context as inner biological and psychological structure, or “essential structure”. There are plenty of places and times in the history of science when it has been reasonably supposed that theory grasped the essential nature of reality. To name but a few: Newtonian mechanics, the mature period table of elements, and the biomedicine of cholera. Also, by way of contrast, in plenty of occasions it did not seem so, such as in the relation between general relativity and quantum mechanics, the models of global warming, the developmental pathology of most medical conditions, the biomedicine of some cancers, and most or all psychiatric conditions. From a pragmatic point of view, the difference here is a matter of how much the science predicts: in the former kind of case, the theory predicts everything of interest (at the time), while in the latter the theory doesn't at all, or we have a range of sub-theories predicting more or less within sub-domains of interest, but no unified theory. When the idea of truth as correspondence is working in the background, however, the theories which predict everything of interest (at the time) appear as its exemplars, illustrating that our concepts can and therefore should grasp the nature of reality as it really is. In practice, in the sciences, it has become obvious, since the demotion of Newtonian mechanics and the absence of a unified physics, that scientific theories don't stay the same but evolve for many reasons, so it would be rash – misconceived – to say that science grasps reality as it really is, once and for all. We can say that it provides better and better approximations, but this comes down to: it gets better at predicting. Prediction is useful in its own right, but of special interest are predictions that help us solve problems, those that underpin interventions. Science is closely tied to utility and technology. Psychiatric classification is supposed to have clinical utility. A particular diagnosis is supposed to provide some information useful for clinical management, such as course and prognosis with and without particular treatment(s). By all means diagnoses are only partly successful in this, more or less so depending on the condition, subtype and which treatment. Nevertheless, in the clinic, we suppose that the current diagnostic system guides management somewhat, even if imperfectly, better than nothing, and better than any other system on offer. Onto this shifting problem domain of clinical utility, Jablensky proposes two criteria of “validity”. One of them is that to be valid a condition must be discrete, separated from others by a “zone of rarity”. This sounds to me like the correspondence theory of truth at work again, because this theory supposes that facts and therefore their representations are discrete, each identical to itself and to no other thing. So far as utility is concerned, however, fuzzy overlapping categories can still be useful, more or less, and might be all we have to go on. The weather can be forecast, more or less well, for a limited time ahead, by cloud-shape types (by all means not by shapes of individual clouds), even though not precisely defined and sometimes muddled together. The other criterion of validity Jablensky proposes is mapping on to the science. He cites the diverse criteria for establishing validity of diagnoses proposed by Robins and Guze, Kendler, and Andreasen. These include, to name but a few, familial aggregation, typical precipitants, psychological tests, neurochemical assays, as well as rates of relapse and recovery, and response to treatment. In these lists, clinical utility appears as validation marker, which, in the view being proposed here, it should, there being no fundamental conceptual distinction between utility and validity. Both utility and validity come to the issue of how much of interest is predicted, and among that, the critical issue of how the predictions guide action and underpin technological solutions. So what do we expect of scientific validity criteria such as genetic, neurochemical, neurological or neuropsychological? We expect these to be useful too and value them for this reason. We do not expect them just to “map onto reality”, otherwise understood. As mentioned earlier, the biomedical model of cholera can be reasonably described as pinning down the real nature of the disease, but this description is underpinned by the fact that the model delivers everything of interest, specifically models of and technologies for treatment and primary prevention. Increasingly we know that the causes of psychiatric conditions – along with the causes of many general medical conditions – are not singular but multi-factorial, and moreover may have a development from birth, given that genetic predispositions are life-long, some modifiable by epigenetic mechanisms. Models of these multi-factorial life-longitudinal pathways, for example for cardiovascular disease or clinical depression, are more complex than for infectious diseases, but what we expect of them is the same, namely, identification of correlations and modifiable targets for treatment and primary prevention. The science – behavioural or molecular genetics, psychological tests, neurochemical assays, neuroimaging findings – has to be judged against these pragmatic criteria, just as psychiatric classification has to be judged against findings in the science. The argument cuts both ways. It has turned out that there is a poor mapping between emerging genetic, neurological and neuropsychological biomarkers and current psychiatric classification. For a while this of course looked like bad news for the biomedical model's application to psychiatry, until the realization that the poor fit could just as well be interpreted as bad news for the classification system. This latter interpretation drives the U.S. National Institute of Mental Health's Research Domain Criteria project2, 3. Current diagnostic criteria no longer are a gold standard; they have to prove their worth in the new sciences, to be conducted on the presumed underlying biopsychological structures and functions themselves. Nonetheless, the pragmatic demands – the requirement of clinical utility, broadly conceived, to include also early detection and primary prevention – remain. Ultimately health science, as opposed to science conducted for some other interest and technical application, has to relate to health and disease. In this connection the Research Domain Criteria project has been challenged for losing firm grip on “disease”, both conceptually4 and for the purposes of global mental health strategy5. The current psychiatric classifications, whatever other shortcomings they may have in relation to clinical utility and biomarkers, do at least serve the major practical purpose of defining diseases (illnesses, dysfunctions or disorders), conceived as conditions typically associated with significant burden of distress and impairment of functioning, hence requiring health care attention, and which are the essential outcomes of interest for health care provision and prevention strategies, and for national economies. Derek Bolton Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK