This book is the publication of a conference held at the Institute of Psychiatry in London on 20-22 June 2007. The conference was the tenth in a series of National Institute of Health (NIH) funded research planning conferences for DSM-V – the fifth revision of the Diagnostic and Statistical Manual of the American Psychiatric Association, due for publication in May 2013. Twenty-three invited scientists from around the world participated.

The aim of the conference was to help decide whether major depressive disorder (MDD) and generalized anxiety disorder (GAD) should continue to be regarded as separate categories, as they were in DSM-IV and DSM-IV-TR. The proposal for change would see MDD and GAD, although they would continue to be separate disorders, combined into the same group, which would be distinguished from fear disorders and could be called either distress disorders or anxious misery disorders. This new grouping would itself be a subcategory of a higher order category called either emotional disorders or internalizing disorders. In other words, GAD would be switched to be in the same group as MDD rather than be classified as currently with the fear disorders under anxiety disorders.

The papers examine data to help decide how closely related MDD and GAD are on the basis of genetics, biology, treatment, development, course, predictors, disability and psychosocial stressors. Decisions about classification on this basis are not totally empirical, if only because data indicators do not always agree. They are also only indicators and rarely, if at all, have one-to-one correspondence with the relevant mental disorder.

It’s all very well hoping that we can find biomarkers for functional mental disorders but as yet we do not have any, and are probably never likely to do so. We, therefore, need to make do with fuzzy boundaries between psychiatric syndromes. There is no “point of rarity” between different diagnostic categories that can be established empirically. It’s a myth to think there are natural kinds of mental disorders.

Diagnostic concepts are in fact simply categories justified by clinical utility. They are working concepts for clinicians. To give the authors of this book their due, they do in essence recognize this. The mass of data presented may suggest otherwise because it could be said that there seems to be an underlying assumption that diagnoses do represent entities of some kind. It’s misleading to make this inference. However tempting it is to think that there must be an underlying disease at the back of it all, we should acknowledge that this is wishful thinking.

Classificatory systems are likely to continue to change to reflect the hypothetical constructs that we create. But they’re idealized descriptions and however much we think the empirical data impinges on these constructs, this is unlikely really to be the case. The “empirical” argument may merely serve as a justification for a decision, which is open to interpretation and for which there will be different views.

It’ll be interesting to see how DSM-V takes this issue forward as regards the overlap between anxiety and depressive disorders. There always has been and will be an overlap to reflect in whatever classificatory system is created. DSM-V may do it differently from DSM-IV and DSM-IV-TR. If it does, it will have taken a radical step; if not, a more conservative step. Whichever it does — and I would have thought the current indications are that DSM-V is more likely to be conservative on this issue and still separate mood and anxiety disorders at a high level in the classification —  the “real” world won’t have altered. What will have changed is just how we think about it in terms of the classificatory system, which can have implications for how patients’ problems are constructed.

© 2011 Duncan Double

Duncan Double, Consultant Psychiatrist and Honorary Senior Lecturer, Norfolk Mental Health Care Trust and University of East Anglia, UK; Website Editor, Critical Psychiatry Network.