Mental Retardation, Dementia, and the Age of Majority

By Chris Borthwick

Reprinted with thanks from Disability & Society, Vol. 9, No. 4, 1994

ABSTRACT

DSM-III-R, the standard psychological diagnostic manual, distinguishes between ‘Mental Retardation’ and ‘Dementia’ solely on the basis of age of onset. A similar clinical picture arising before the age of three constitutes one condition, one arising between the ages of three and eighteen both conditions, and one arising after the age of 18 the other condition. The other criteria for the two conditions have little in common and are in some aspects contradictory. The question arises whether a condition with such protean presentation can be said to constitute an entity, and it is suggested that the category of ‘Mental Retardation’ be discarded in favour of descriptors that are both more precise and do not attempt the function of a universal explanation for all behaviours.

According to Borges, the ancient Chinese encyclopaedia The Celestial Emporium of Benevolent Knowledge divides the animal kingdom into the following categories;

We find the Borges list odd because we expect classification systems to not only list items falling under a single heading — animals, say, or people with mental disorders — but to provide a structure in which these items can be related to each other in terms of a common scale of relation to the broader category. Neither The Celestial Emporium of Benevolent Knowledge nor the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) meets these expectations. Any discontinuities in the Celestial Emporium have long since ceased to trouble us. DSM-III-R still shapes our beliefs about ‘Mental Retardation’ and the services we provide to people we diagnose on the basis of DSM-III-R criteria as having that ‘condition’. In particular, the DSM-III-R category of ‘Mental Retardation’ claims not simply to describe a condition but to explain the behaviours of people who are diagnosed as having it, and that overriding explanation has led to a neglect of any search for more specific explanations for particular behaviours.

DSM-III-R, the standard nosological text in the field of psychology, has as its primary categories

Of these, ‘Disorders Usually First Evident in Infancy, Childhood, or Adolescence’. seems particularly anomalous, belonging to a classification system conducted on different principles from the remainder of the list. This category is distinguished not from the other possible chronological divisions (“Disorders Usually First Evident in Adulthood”. for example, or “Disorders Usually First Evident in Old Age”) but from

This system of categorization has functioned in some form or another for forty years. It has served to compartmentalize the field in a manner that discourages comparison between different regions and thus conceals internal contradictions. The system both assumes and reinforces the reification of the conditions it distinguishes. In particular, DSM-III-R and its predecessors have had an immense influence on the manner on which intellectual impairment — difference in cognitive functioning — has been conceptualized as ‘Mental Retardation’.

An important element in this construction has been the disposition of ‘Mental Retardation’ within the DSM-III-R schema. DSM-III-R places ‘Mental Retardation’ in the category of ‘Disorders Usually First Evident in Infancy, Childhood, or Adolescence’. Its essential features are given as

These criteria are to a large extent circular. ‘Mental Retardation’ is, in its essence, ‘subaverage general intellectual functioning’, which is simply a paraphrase of ‘Mental Retardation’. The criteria contain no information not contained in the name ‘Mental Retardation’, and rely for their diagnostic significance on the unwritten assumptions that that name embodies.

These assumptions emerge most clearly in the criteria for the sub-diagnoses. ‘Mental Retardation’ can be severe, moderate, mild, or unspecified. In the last of these, ‘Unspecified Mental Retardation’

Considered simply in terms of the classification system, this is meaningless. A presumption of ‘Mental Retardation’ must, in terms of the criteria, mean a presumption that (inter alia) a person has a measured IQ of below 70. There are no test-independent criteria to appeal to; if there were, the IQ test would not be necessary. The diagnosis of ‘Unspecified Mental Retardation’ can be supported only by reference to the unwritten but well-understood concept of ‘people who look and behave like other people diagnosed as mentally retarded’. It would seem that we know who the people with ‘Mental Retardation’ are; the function of the criteria is to avoid excluding any of the cases we have already decided belong in the classification. In the final analysis, the diagnosis of ‘Mental Retardation’ relies not on any specified criteria but rather on the subject’s conformity with a social stereotype.

The concept of mental retardation has been under attack for many years. A number of studies have drawn attention to the preconceptions that govern the manner in which the label is applied. Bogdan and Taylor have gone still further, saying that

It may be of assistance in this context to demonstrate that the core concepts of ‘Mental Retardation’ are in their official incarnations conceptually incoherent — more specifically, that the consistency of DSM-III-R is undermined by its incorporation of chronology into its classifications.

Most textbooks on ‘Mental Retardation’ quote the DSM-III-R triad and proceed from there without devoting any further time to questions of definition. Others draw attention to such controversies as the debate between proponents of pure IQ scoring and those who want adaptive behaviour measures given equal weight. Almost always the case, however, the discussion is left incomplete. One leg of the triad — the requirement that the condition come into existence before the age of 18 — appears to be virtually invisible.

No justification is provided in DSM-III-R for the selection of the age of 18; the manual simply states that

The setting of an upper age limit is thus no less arbitrary than the setting of an upper IQ level, but while there has been continued discussion on the point on the IQ scale that should mark the boundary between disability and normality there has been almost no discussion of the significance of the age boundary between ‘Mental Retardation’ and what comes after.

What comes after, according to DSM-III-R, is ‘Dementia’.

The criteria for ‘Dementia’ are markedly different from those of ‘Mental Retardation’; they do not, for example, include significantly subaverage general intellectual functioning. It is simply not possible to acquire significantly subaverage general intellectual functioning after the age of 18. If you are subaverage, you must be subaverage in different ways according to different criteria. This is not entirely satisfactory. There must be some questions as to the degree of reality to be accorded to a condition whose presence or absence depends on whether it occurs on the Tuesday before your eighteenth birthday or the Thursday after. Even more oddly,

Even if the person did not previously have normal intelligence, ‘Dementia’ is still a possibility. The only requirement is that onset be

— in practice, that the child be old enough to have had an IQ score taken, in order that a loss of intelligence can be demonstrated.

Three individuals with identical clinical presentation stand in a line. One person acquired a chronic neurological disorder at age two, and has ‘Mental Retardation’, one acquired the disorder at the age of seventeen, and has ‘Mental Retardation’ and ‘Dementia’, and one acquired the disorder at the age of nineteen, and has only ‘Dementia’. One could, alternatively, imagine a person whose history dictates the byzantine combination of ‘Mental Retardation’ (a neurological disorder at the age of, say, two, leading to an initial IQ score of 69), ‘Dementia’ (a further neurological disorder at the age of eight, leading to a fall in IQ scores from 69 to 60), and the additional handicap of ‘Developmental Reading Disorder’ (where

The degree of overlap specified in DSM-III-R is sufficient to prompt the question ‘Are ‘Dementia’ and ‘Mental Retardation’ two conditions, or one?’

In DSM-III-R the two conditions are distinguished, age limits aside, by the fact that ‘Dementia’ is an ‘Organic Mental Disorder’ and ‘Mental Retardation’ is not. One grouping is associated with damage to the brain, one with damage to the mind; ‘Dementia’ is thought of as physical, ‘Mental Retardation’ as other than physical. DSM-III-R is, to be sure, somewhat embarrassed by the metaphysical associations of these terms, and states at one point that

but the grouping does nonetheless accord with a long tradition of conceptualizing intellectual disability as the possession of a different and lesser variety of mind rather than a normal mind damaged.

Whatever disclaimers DSM-III-R includes, the distinction between organic and non-organic mental conditions has become so embarrassing that the American Psychological Association Task Force on DSM-IV now proposes to abolish it.

The elimination of this longstanding distinction leads, however, neither to a reconsideration of the status of conditions

previously regarded as so organic as to be medical rather than psychiatric nor to any major regroupings within existing classifications.

Under the second option, the grouping is to survive even though no common heading, no relation to each other at all, can be found for its components. Under the first option the proposed common heading of ‘Cognitive Impairment Disorders’ shares precisely the problem that led to the abolition of the previous heading. A grouping of ‘Organic Disorders’ suggested that other conditions were not organic; a grouping of ‘Cognitive Impairment Disorders’ suggests that other conditions do not involve cognitive impairment. Once again, disclaimers are made.

It is also the predominant feature, by any definition, in ‘Mental Retardation’, which is not given as an example. Why, then, is ‘Mental Retardation’ not placed in this classification? To say that it is ‘Usually First Evident in Infancy’ hardly constitutes an answer; as the Options book says,

and in recognition of this the Options book in fact proposes to alter the title of the classification to ‘Disorders Usually First Diagnosed in Infancy, Childhood, or Adolescence’, in that while there are other early onset problems these

That is to say, two of the broad DSM-III-R classifications — ‘Disorders Usually First Evident in Infancy, Childhood, or Adolescence’ and ‘Organic Disorders’ — have proved to be non-viable groupings, in that they are headings that do not in fact identify a common and distinctive feature in the sub-headings. In both cases the response has been to alter the name of the grouping in an attempt to better describe its existing contents rather than to reshuffle the sub-conditions to the existing headings — organic, early onset — they belonged in. The groupings seem to be taken as primary and immutable, although it has had to be conceded that our ideas as why it is that the conditions inside them are similar may change from time to time.

If the groupings were not thus immutable, ‘Mental Retardation’ would certainly seem to belong in the ‘Cognitive Disorders’ section; in fact, the main effect of the existence of a grouping named ‘Disorders Usually First Evident in Infancy’ is to ensure that ‘Mental Retardation’ is not placed in the ‘Cognitive Disorders’ section.  If the two conditions existed side by side in the classification system, as they apparently do in individuals who acquire ‘Mental Retardation’ between the ages of six and eighteen, would they be seen as two conditions or one? If they are the same condition at different ages, their names and their places in the classification systems should reflect their kinship. If they are separate conditions, why does one replace the other at a certain age?

What exactly is meant by the phrase ‘a similar clinical picture’? The criteria for the two conditions are far from similar. ‘Dementia’ has symptoms, while ‘Mental Retardation’ has only outcomes. DSM-III-R ascribes ‘Dementia’ specific malfunctions;

These symptoms have been tightened and made more precise in the proposed revision.

The new criteria are not without their own problems with chronology. It can be seen that the new definition incorporates chronological references in both directions; if you are born with memory loss, apraxia, aphasia, and agnosia, have always functioned at a low level, and therefore have nothing to decline from, you do not, under (C) have dementia, and if you acquire memory loss, apraxia, aphasia, and agnosia but nonetheless recover then you did not, under (B) have dementia. Neither chronological component seems, on analysis, very helpful.

Nonetheless, the criteria for ‘Dementia’ do appear likely become more specific in DSM-IV. In contrast, the criteria for ‘Mental Retardation’ are to remain virtually unaltered, the condition still being characterized only by its consequences — IQ scores of 70 or below, deficits in adaptive functioning — and its age limit, rather than by any characteristics of the condition itself.

The criteria for the two overlapping conditions are thus clearly distinct. In practice, the difficulties that might otherwise be posed in a given individual by this divergence are generally resolved by ignoring the DSM-III-R prescriptions.

If this escape was not open, the differences in diagnostic criteria would have considerable practical significance. A finding of ‘Dementia’ involves the presence of such cognitive defects as apraxia, aphasia or agnosia. These defects in a person should in themselves rule out the administration of the standard intelligence tests required to support a diagnosis of ‘Mental Retardation’.

A dual diagnosis of ‘Dementia’ and ‘Mental Retardation’ is conceivable only in the abstract; once the necessary testing procedures are specified it can be seen they are mutually exclusive. Identical tests, for example, are performed to test for apraxia and to test for intellectual disability.

The same outcomes, however, on the same tests, have a different significance depending on what condition is being tested for. A poor result on a neurologically-oriented blocks test signifies the presence of apraxia (with, perhaps, unaffected ‘intelligence’) while a poor result on a psychologically-oriented blocks test signifies the presence of intellectual impairment.

The conceptual difficulty highlighted by this comparison is that

The inconsistency between these overlapping classifications would be a more pressing practical problem if both were not employed primarily as post facto rationalizations of judgements reached on the basis of prior expectations. Even so, however, it is surely important to decide which of the two approaches to mental dysfunction provides the best account of the condition.

The distinction between brain inadequacy and brain damage is not simply a matter of the lesser stigma attached to the latter. Damage — the diminution of an already measured level of functioning — brings the client within the ambit of neurology rather than psychology. Different factors are taken to be relevant, different conclusions are drawn from the evidence, the condition has a different epistimological status. ‘Dementia’ is seen as naming a range of forms of inadequacy, ‘Mental Retardation’ as an explanation for inadequacy. ‘Developmental Writing Disorder’, for example, is

Poor performance in reading not falling under the heading of ‘Developmental Writing Disorder’ is said to be ‘explained’ by poor performance at IQ tests. In ‘Dementia’, by contrast, while a person who performs poorly in word recognition tasks may have ‘aphasia’, the term does not claim to explain the dysfunction as much as name it; ‘aphasia’ is simply the term that identifies the particular disability manifested by, inter alia, poor performance in word recognition tasks.

If a person falls into the age group set aside for ‘Mental Retardation’, test failures are seen as indicating a global incapacity unless internal IQ inconsistencies suggest learning disabilities. If the impairment is acquired rather than congenital it is assumed simply that the person has the particular cognitive disabilities that they demonstrate; it is even recognized that it is possible for a person to have a pattern of specific disabilities that mimic ‘intellectual disability’ — a combination of aphasia, say, affecting language testing, and apraxia, affecting non-language testing — leading to identical results on standardized tests and having a similar effect on social adjustment but leaving higher cognitive processing unimpaired. Neurological diagnoses such as apraxia and aphasia are less sweeping and less judgemental than psychological assessments, and one of the key questions in any discussion of the construction of intellectual disability is why the insights of neurology have not generally been considered to be relevant. One one level, of course, the organic/non-organic division in DSM-III-R made neurology irrelevant by definition to non-organic conditions, but that explanation only shifts the question back to the reasons for the evolution of that convention

It has been almost universally accepted as axiomatic that there is a single entity that is intellectual disability, and the arguments that take place are arguments over how this entity shall be defined and where its boundaries lie. If we did not, as we do, see ‘Mental Retardation’ as a fact of nature, how would we have gone about describing it? What common factors , without that assumption, would we have been able to identify?. Would we have evolved a single grouping at all? Would the identifying features of our grouping — poor expressive language skills, apparent memory problems, learning difficulties — meet the requirements of a syndrome, let alone a condition? In this respect ‘Mental Retardation’ may be compared to the hypothetical medical syndrome PFSD, for ‘pain/fever/spots/dizziness’. In such a syndrome there would be core examples of the condition, people who had pain and fever and spots and dizziness and thus met all four of the criteria, and there would be atypical examples who had one only but who we might nonetheless wish to catch under the heading for purposes of service delivery. Such a syndrome would obviously be multi-etiological (although this would not automatically make it suspect; compare, for example, ‘Autism’) and would be a loose syndrome where absolute precision in diagnosis could not be expected and some disagreement was inevitable. Estimates could nonetheless be made at least of its administrative prevalence, and it would doubtless be said of it that

The question that might not necessarily be asked once a service system was in place would be whether the appearance of such a condition arose only from the frequent coincidence of what were nonetheless unrelated incidents. It is possible to be, like PFSD, to be a discrete and definable category while still being made up of a random number of unrelated segments — to be a syndrome without being an entity.

Even this comparison, however, flatters ‘Mental Retardation’. The concept of ‘Mental Retardation’ lacks sufficient cohesion to make it a meaningful diagnosis. People with Mental Retardation’ are defined not in terms of the positive criteria they have in common but on their difference from the norm, on the basis of things that most people can do and they cannot. Such negative definitions do not necessarily imply much commonality among the outgroup. If the car is taken as the standard then bicycles, trains and horses might be classified together as non-four-wheeled transportation; in the absence of the defining other, the resemblance of each to each and the difference of each from carts or rollerskates would not be evident — would not be evident, at least, unless we had only one name with which to cover all three forms.

In the area of ‘Mental Retardation’, there is effectively only one name (there are, to be sure, a large number of terms — mental retardation, intellectual disability, mental handicap — competing to be that one name, but these alternatives are exclusive, not complementary). One of the most striking features of the history of the study of ‘Mental Retardation’ over the past ninety years is that it has evolved almost no internal divisions. We have, rather, an enormous variety of etiologies; but all roads lead to Rome, and all etiologies evidently give rise to the same condition. One can only imagine how far neurology would have progressed over the same period if Wernike’s aphasia, cortical blindness, Tourette’s syndrome and Broca’s aphasia all had to be described without differentiation as ‘brain damage’.

We have not sought for differentiation within ‘Mental Retardation’ because we have believed in an explanatory entity. If this entity is abandoned we may begin to identify particular deficits. There are certainly people who have from early life greater than average difficulty in performing certain sequences of mental and physical operations, and in whom the source of the difficulty appears to be located in the skull; the question remains open as to whether these people have any more in common than that.

If we were writing DSM again without any preconceptions, would we be able to find a more parsimonious concept than general intellectual defect? Would we replace a unitary ‘Mental Retardation’, however defined, with a number of smaller separate entities? If we were beginning from first principles, would we have commenced with intellectual evaluation at all? People with intellectual disability may have motor or linguistic problems. DSM-III-R says that

There is, that is to say, an association between physical abnormalities and ‘Mental Retardation’. Such an association can point two ways. If we were beginning again, could we envisage the DSM-III-R relationship the other way round — the more severe the physical abnormality, the greater the chance of being diagnosed as having severe or profound ‘Mental Retardation’? Once we had framed the relationship in that form, might we then ask whether the influence of physical abnormality might contribute to an appearance of intellectual disability (take the form, say, of additional difficulty in taking standard intelligence tests)?

Even if we thought it was unlikely that motor defects alone could produce a successful simulation of all cases now grouped under ‘Mental Retardation’, would making allowances for the the effect of such a handicap reduce the extent of the difference between the ‘normal’ mind and the hypothesized ‘generally defective’ mind? Given a lesser difference, might we have attempted to construct the condition from pre-existing components — memory disturbance, apraxia, aphasia, agnosia — rather than creating a whole new mind to account for it? Might we not have come up with something rather like the proposed definition of ‘Dementia’? Do we need ‘Mental Retardation’ at all? Do we need the term ‘Dementia’ — stigmatizing, vague, and adding to the subconditions of which it is composed only further chronological complications?

The preconceptions that shape our present classifications have not been generated from discussion, or even subjected to discussion. A reality that corresponds to ‘Mental Retardation’ is taken for granted; indeed, mental retardation may almost be defined as that area of deviancy that is taken for granted. Historically, socially, and geographically ‘Mental Retardation’ is what is left over when

have been taken out of asylums (all these groups have at one time or another shared the asylums with people with intellectual impairment) and sexual deviants, deaf people, people with mental illness, paupers, people with cerebral palsy, habitual drunkards, consumptives, unmarried mothers on welfare, epileptics, habitual criminals, drug addicts and people engaged in the white slave trade (all these groups have been targeted by eugenicists) have been removed from the sanctions imposed on the feebleminded (Kevles, 1985). As we have successively become conscious of each group its placement within ‘Mental Retardation’ has appeared anomalous and it has been removed. What remains after each successive extraction is specifically the unexamined, the group that does not arouse questions, the group that seems a ‘fact of nature’ and is not seen as the outcome of a social process. The ‘fact of nature’ serves as an explanation of subordination and a justification for differential treatment.

One of the considerations associated with the distinction between the neurological model and the psychological model of disability is the presence or absence of rights; it is not necessarily a coincidence that the boundaries of ‘Dementia’ coincide with the age of majority. It is time to concede to these people the right to be freed from a classification that stigmatizes them, denies their specific impairments, and conceals their individual potential. The term ‘Mental Retardation’ should in future be used only as part of the phrase ‘diagnosed as mentally retarded’, a reference to a social condition rather than a characteristic of the person. If we are called upon to name more precisely the condition of people so described the least that they have a right to expect is that we will attribute to them their own individual cognitive problems rather than those of a carelessly drawn social stereotype. ‘Mental Retardation’ is to, say, ‘apraxia’ as ‘act of god’ is to ‘road trauma’ — a transferring of manageable contingency into the realm of the unchanging and inevitable. We are moving these people out of segregated settings back into the community; it is time we desegregated their diagnoses and appraised their problems not against the name we created to explain them but against the same conditions we are prepared to attribute to other people in the community.

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