The nosology of mental disorders inevitably dithers between the wish to delineate useful categories and the hope of discovering natural kinds. It would be good to achieve both but each aspiration alone is elusive enough. Indeed, some would reckon the second hope to be forlorn and there has been a tendency to emphasise the pragmatic and the descriptive. The current classifications—ICD-10 and DSM-IV—are the offspring of this tendency (WHO, 1992; APA, 1994). Yet there is a nagging feeling that there are ‘real’ disorders out there to be discovered rather than merely defined.
Within the field of eating disorders, anorexia nervosa crystallised out as a separate and distinct disorder over the course of the last century (Mount Sinai, 1965). It had the advantage of one criterion that was both undisputed and easy to measure, namely low weight. However, it was the description of the characterising beliefs and behaviours that led to the disorder being separated off from other states with weight loss.
Furthermore, it was the description of similar beliefs and behaviours in people of unremarkable weight that led to the definition of bulimia nervosa and its relatives. However, it is arguably when the definition of mental disorder relies upon the mental state—as it almost inevitably should—that classification becomes more difficult.
Can we really measure people’s thoughts and feelings reliably and is it reasonable to expect that they should fit neatly into categories? Even classifying behaviour is problematic enough. However, if we do observe that people come to suffer in similar ways and with similar beliefs then this may give clues not only about sociological generalisations but also, perhaps especially, about innate and probably biological mechanisms which may underpin their disorder.
People may come to be more similar when they are stuck within a morbid process than when they arc well because the range of their behaviour and experience is at least in part constrained by potentially definable processes in which such biological mechanisms arc playing some limiting part. Tolstoy wrote, ‘all happy families resemble one another, but each unhappy family is unhappy in its own way’.
This is questionable even with regard to families and unhappiness, but with individuals and disorder it seems likely that the reverse is true. The range of what is morbid is narrower than the range of the non-morbid. Antipsychiatrists tend to emphasise the prescriptive nature of ‘normality’ and to portray the person who is ‘labelled’ mentally disordered as something of a free spirit. However, the psychiatric perspective is different.
The patient suffering from a mental disorder is seen as constrained and trapped by forces that are outwith his or her control. It is the sufferer who is the tram compared with the normal person who resembles the bus in having much more freedom. Both the bus and the tram are limited by their physical attributes but the tram is additionally constrained by the rails. Study of the patterns of disorder could give clues as to the nature of these Tails’.
So what is the status of our current attempts at classification? What patterns can we discern in people with eating disorders? How well doourconvcntional diagnoses map these patterns? And do any of these patterns suggest the presence of plausible mechanisms of actiological significance? Do our categories promise to be more than convenient pigeonholes? Are there ‘real’ disorders out there?
What follows is a clinician’s view of our present classifications and some speculation about what mechanisms and natural kinds might lurk beneath the surface of their syndromes and diagnostic criteria.