diagnostic criteria

Journal of Intellectual Disability Research

pp

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Blackwell Science, LtdOxford, UKJIDRJournal of Intellectual Disability Research

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Blackwell Science Ltd,

Supplement

Original Article

DC-LD and the diagnosis of anxiety disorders

N. M. Bailey & T. M. Andrews

Correspondence: Dr N. M. Bailey, Fiveways ResourceCentre, Ilchester Road, Yeovil, Somerset BA

BB, UK(e-mail: [email protected]).

Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities/Mental Retardation

(DC-LD) and the diagnosis of anxiety disorders: a review

N. M. Bailey

1

& T. M. Andrews

2

1

Somerset Partnership NHS and Social Care Trust, South Somerset Community Team for Adults with Learning Disabilities, Yeovil, Somerset

2

Oxfordshire Learning Disability NHS Trust, Headington, Oxford UK

Abstract

Background/Methods

During the development of

Diagnostic Criteria for Psychiatric Disorders for Use with Adults with Learning Disabilities

[DC-LD] a literature review of diagnostic issues in anxiety disorders in adults with intellectual disability (ID) was undertaken using electronic and hand searching of journals.

Results

Relevant general concepts in the general population are reviewed briefly before those related specifically to adults with ID. The literature relating to the diagnosis of specific anxiety disorders is reviewed, although with the exception of obsessive compulsive disorder this consists mainly of case reports. Difficulties in the use of diagnostic systems developed for the general population for the diagnosis of anxiety disorders in adults with ID are frequently commented upon.

Conclusions

It is concluded that anxiety disorders are well recognized in adults with ID, although their prevalence is uncertain, and that the use of modified diagnostic criteria may aid further research in this area.

Keywords

adults, anxiety disorders, diagnosis, mental retardation

Introduction

This literature review was part of the work undertaken to develop Diagnostic Criteria for Psychiatric Disor-ders for Use with Adults with Learning Disabilities [DC-LD] (Royal College of Psychiatrists

) and so its focus is on the assessment and diagnosis of anxiety disorders in adults with ID, rather than the treatment of such disorders. The concept of anxiety disorders for the purpose of this review is largely that in the section ‘neurotic and stress related disorders’ of DC-LD (corresponding to the block ‘neurotic, stress related and somatoform disorders’ of the Interna-tional Classification of Mental and Behavioural Dis-orders [ICD-

] (WHO

). However, literature relating to acute stress reactions, adjustment disorders and post-traumatic stress disorder will not be dis-cussed here. Similarly, literature regarding the presen-tation of anxiety disorders in children is not included.

Classification

The problem of classifying anxiety disorders in the general population disabilities is far from easy. This,


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N. M. Bailey & T. M. Andrews •

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in part, relates to the fact that anxiety is a symptom that may occur in a number of clinical syndromes that probably have a heterogeneous aetiology. It is com-plicated further by the fact that anxiety is a universal experience which only becomes pathological when its extent or degree exceeds a certain threshold. Bond

et al

. (

) concluded that pathological anxiety involved an increase in arousal that was irrelevant to a given task and had a disorganizing rather than facil-itating effect on performance.

Evolutionary perspective

It is highly likely that anxiety and fear are adaptive responses that have developed through evolution over a long period of time. For this reason, fears of snakes, spiders, high or open spaces are more common than fears of cars or cigarettes, although the latter are responsible for more deaths in modern society. There is evidence that anxiety responses are present from an early stage in development. However, it is more difficult to define when these responses become excessive or pathological. When fear is aroused by an immediate threat (for example being attacked) then increased sensitivity to warning cues is obviously adaptive. Oversensitivity of these mechanisms in the absence of immediate threat is one possible mechanism underlying pathological anxiety states (Mathews

).

Biological aspects

A number of neurotransmitters have been implicated in the aetiology of anxiety, most notably

-HT (Iverson

), noradrenaline (Sevy

et al

.

) and GABA (Crestani

et al

.

). It has been postulated that functional anatomy of anxiety involves amygdala-based neurocircuits with critical reciprocal connections to the medial prefrontal cortex. Traumatic experiences may leave emotional imprints involving the amygdala, with facilitated fear-conditioned associations involving declarative memory traces (Ninan

).

Psychological theories

Beck & Clark (

) proposed that anxiety disorders resulted from ‘dysfunctional schemas’ derived from past learning experiences of an individual. For exam-ple, people with panic disorder tend to misinterpret bodily sensations as a sign of immediate catastrophe

(Clarke

) and thus have assumptions about the dangerous nature of bodily functions.

Wells & Matthews (

) proposed a ‘dual level theory’ of information processing. ‘Lower level’ pro-cessing occurs automatically and involuntarily with little limit on attentional capacity. ‘Upper level’, or controlled, processing involves a plan or strategy and is limited by attentional resources. How these theo-ries apply to people with ID is not discussed, but many cognitive theories of anxiety disorders may be difficult to apply to people with more severe ID.

Prevalence

There is little doubt that anxiety disorders exist in people with ID (McNally & Ascher

). How they have been diagnosed and classified together with the populations studied leads to considerable variations in the rates reported from

.

% (Crews

et al

.

) to

.

% in an institutional population for anxiety disorders diagnosed by Psychopathology Instrument for Mentally Retarded Adults [PIMRA] and DSM-III (American Psychiatric Association

, Linaker & Nitter

).Many studies fail to make a definite diagnosis and

report only the prevalence of anxiety symptoms, which range from

% (Ballinger

et al

.

) to

% (Reiss

). With more severe ID only behavioural symptoms can be assessed reliably and this often makes it difficult for all the criteria of an anxiety disorder to be met (Matson

et al

.

).

Method

Electronic searching

A computerized literature search was undertaken using the databases PsychINFO and Medline for English language articles up to October

.

PsychINFO

The following strategy was employed: [(explode ‘mental retardation’) or (ment* retard*)] and (explode ‘anxiety disorders’).

Medline

The following strategy was used: [(explode ‘mental retardation’/all subheadings) or (mental retardation)] and (explode ‘anxiety disorders’/all subheadings).


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Handsearching

In addition the following journals for the last

years were searched by hand for articles relevant to diag-nosis of anxiety disorders in adults with ID:


,

American Journal on Mental Retardation

,

Journal of Nervous and Mental Disease

,

British Journal of Psychiatry

,

Irish Journal of Psychological Medicine

,

British Journal of Developmen-tal Disability

,

Psychological Medicine

,

Journal of Applied Research in Intellectual Disability

,

Journal of Intellectual and Developmental Disability

,

Mental Retardation

,

British Journal of Learning Disabilities

and

Psychiatric Bulletin

.Relevant articles cited in those found by this

method were also included. Articles that did not refer to adults with ID were excluded.

Results

From the electronic search strategy,

papers were found. A further

papers were found from hand-searching. From looking at the abstracts, papers that were considered to be relevant were requested. After further discussion between the authors,

of the total

papers were finally felt to be relevant to this review. Included articles referred either to assessment or diagnostic issues, or to specific anxiety disorders if no other articles were available on that disorder. The included studies have been subdivided into those that mention diagnostic issues in anxiety disorders and ID and those that refer to subcategories of anx-iety disorders in adults with ID.

Diagnostic issues

Diagnostic overshadowing

It was proposed by Reiss and colleagues in the

s that clinicians were much less likely to recognize additional psychiatric disorders when they presented in people with ID. The term they used for this con-cept was ‘diagnostic overshadowing’, and it was sug-gested that it occurred in two ways: first, that the clinicians did not notice the features of an additional psychiatric disorder in people with ID because the features of intellectual impairment were so over-whelming; and secondly, that when the features were noticed, they were wrongly attributed as being part

of the person’s ID rather than an additional psychi-atric disorder (Reiss

et al

.

). They investigated this experimentally by means of vignettes sent to clinical psychologists, one of which involved a man with a simple phobia, precipitated by a stressful event. They showed that a phobia was significantly less likely to be diagnosed if the vignette involved a man with ID rather than a man from the general population. The terms ‘neurotic’, ‘irrational’, ‘emo-tionally disturbed’ and ‘psychotic’ were found to be applied significantly less frequently in the case of the person with ID. In a later study, Levitan & Reiss (

) used the same vignettes and showed that this phenomenon was demonstrated equally by psychol-ogy students as with social work students and hence was general across professional disciplines. Although the robustness of these findings and the proposed mechanisms for the development of the phenomenon have been challenged (Spengler

et al

.

) a meta-analysis of studies on diagnostic overshadowing has confirmed its existence, although its effect was found to be small to moderate (White

et al

.

). DC-LD is a multi-axial diagnostic system. It adopts a hierar-chical approach both through and within axes. Each axis is considered in turn. For example, if a disorder on Axis I

-

Severity of Learning Disabilities does not account for the whole presentation of the individual, Axis II disorders

-

Cause of Learning Disabilities is considered. This process continues through to Axis III

-

Psychiatric Disorders, and then between the lev-els within Axis III. Such a hierarchical approach to diagnosis may reduce the effects of diagnostic over-shadowing, by obliging the clinician/researcher to account for symptoms in this structured way. Although the ICD-

Guide for Mental Retardation (World Health Organization

) also has multiple axes, it does not adopt a hierarchical approach.

Developmental appropriateness

The types of fears experienced by adults with ID and its relationship with developmental level has been investigated. Sternlicht (

) studied the self-reported fears of

adults with moderate ID. He found that at this developmental age (approximately

–

years) fears of the supernatural and of animals predominated (

% of reported fears), while fears relating to physical injury and psychological stress made up

% of reported fears. He concluded


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that the developmental trend that occurs around – years of age in which there is replacement of Piaget’s stage of preoperational thinking (represented by fears such as those concerning ghosts, thunder and animals) with concrete operational thinking (repre-sented by more realistic fears, e.g. for personal safety or psychological stress) seen in normal children is seen in adults with ID at a similar developmental level.

Duff et al. () compared adults with mild ID and verbal skills with children without ID matched to sex and mental age and adults without ID matched for sex and chronological age. An -item modified Fear Survey Schedule (Wolpe & Lang ) was administered to all groups. Adults with ID reported fear significantly more frequently than adults without ID and significantly less frequently than children without ID. Types of fears were more similar to the mental age-matched control children than chronological age-matched adults. Adults with ID were more often fearful of the following compared with chronological age matched controls (adults without ID): thunder and lightning, cemeteries, hav-ing sex with a man or a woman, crossing streets, hell, being kidnapped, being touched by others and germs. Compared with the mental age-matched controls, more adults with ID reported fear of doctors and more children reported being fearful of being left out and dark places.

Pickersgill et al. () compared adults recruited from ID day centres and thereby assumed to have ID with adults recruited from libraries, cafes and a launderette matched for age, sex and parental occupation. A modified Fear Survey Sched-ule (Wolpe & Lang ) with intensity of fear lim-ited to a three-point scale was used in written form for the non-ID group and administered verbally for the ID group. Four people with ID were excluded due to poor comprehension. The ID group were found to have had higher mean fear rating than the non-ID group and the mean intensity of rating for all fear groups except social rejection (i.e. agoraphobic fears, fears of tissue damage, sex and aggression or animal fears) was significantly greater in the ID group than in the non-ID group. This difference was most marked for animal- and tissue damage-type fears. Although in the non-ID group the usual gender dif-ference of female gender being associated with greater reporting of fears, this was not observed in the ID group.

The authors discuss aetiological factors that may have contributed to the findings of greater levels of fear in the ID group. They comment that socio-economic factors are unlikely to be contributory, given the close matching of parental occupations of the two groups. They suggest that the world is more dangerous in some ways for people with ID than for those without ID for activities such as crossing the road, but consider that such examples are unlikely to account for the overall raised intensity of fear across the fear types in the ID group. They speculate that poorer linguistic skills are influential in two ways: first by resulting in greater difficulties in discussing explaining and moderating or dismissing such fears when they do arise, and secondly by limiting discrimination at a verbal level resulting in over-generalization. They also discuss that over-protection, both parental and institutional, could be relevant, allowing a pattern of learned dependence and hence the development of avoidance as a coping mechanism. It is suggested that the lack of gender difference in the ID group is due to relative discour-agement of the display of masculine characteristics by men with ID due to their social environment.

It is important to note that none of the three stud-ies cited in this section are commenting on clinically significant phobias, but rather on self-reported fears, although the findings are probably relevant to the content of the phenomenology seen in phobias in adults with ID.

Behavioural equivalents

The description of behaviour problems being a manifestation of anxiety disorders is limited to case reports and professional opinion. Khreim & Mikkelsen () comment on the increase in diag-nostic weight that needs to be given to behavioural phenomena in the diagnosis of anxiety disorders in adults with ID compared with the general popula-tion. They give the example, among others, of fear being manifest as ‘agitation, screaming, crying, with-drawal, freezing, or regressive clingy behaviour’. Allen ) reports two studies in which the fre-quency of aggressive and self-injurious behaviour in two individuals (described as having moderate and profound ID) has been reduced by the teaching of behavioural anxiety reduction techniques, including muscular relaxation. Ellison () reports a case of

Journal of Intellectual Disability Research ⁄

N. M. Bailey & T. M. Andrews • DC-LD and the diagnosis of anxiety disorders54

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a young woman with severe ID and generalized anx-iety disorder, panic attacks and agoraphobia who pre-sented with behavioural phenomena of ‘hiding her face, crying, pulling away, refusing to get up from the floor, crouching in the corner, screaming, hid-ing . . . refusing to leave home, frequent urination and smearing of faeces and mucus’. Erfanian & Miltenberger () describe two male adults with profound and moderate ID who had a phobia of dogs and who had placed their lives in jeopardy by the behavioural response to their fear by running across roads when seeing a dog unexpectedly. Perry () reports a young woman who presented with ‘chal-lenging behaviours’ including self-injury, screaming and moaning, pushing staff, attempting to get out of the vehicle and vomiting as a manifestation of fear of travelling in cars and minibuses. DC-LD has addressed the issue by allowing the individual with ID either to describe fear or stating that ‘his or her expression or behaviour may demonstrate anxiety or fear’. ‘Irritability due to anxiety or fear (e.g. physical/verbal aggression)’ is included as one of the readily observable symptoms that can be used to make a diagnosis of generalized anxiety disorder [GAD], the phobias and panic disorder in DC-LD. In the litera-ture on obsessive compulsive disorder [OCD] in adults with ID there is frequent reference to anger or aggressive behaviour occurring when attempts are made by observers to prevent compulsions being car-ried out (Vitiello et al. McNally & Calamari ; Prasher & Day ; Middleton & Cooper ). This phenomenon has been included as one of the criteria for OCD in DC-LD.

Subcategories of anxiety disorder

Agoraphobia

Agoraphobia probably occurs at a rate of about .% in adults with ID (Cooper ) but there is little published on agoraphobia in this population. Wais-bren & Levy () describe five case reports of adults with phenylketonuria [PKU]. Of these, two did not have ID and one appeared to have depression as a primary diagnosis rather than agoraphobia. The two remaining adults had mild ID, PKU and agora-phobia, one of whom responded to the reintroduc-tion of a phenylalanine free diet after failure of drug treatment with clonazepam and propanolol. There is

no comment made on diagnostic issues in adults with learning disabilities and the study used self-report questionnaires devised for the general population, e.g. the Trait Anxiety Scale (Spielberger et al. ), without comment on the appropriateness of this for people with ID. Ellison () described a woman with generalized anxiety disorder with symptoms of panic attacks and agoraphobia. In this case descrip-tion, the authors make the comment that autonomic symptoms of anxiety (for example, sweating and trembling) were observed when she left the home. As she did not speak, it was not possible to obtain a description of her internal state. This problem was considered in the development of DC-LD, which allows either the observation of symptoms of anxiety to the phobic situation or the individual’s subjective description of these symptoms. In addition, the more complex conceptual phenomena such as depersonal-ization/derealization that are included in the list of symptoms in ICD- Diagnostic Criteria for Research (World Health Organization ) are replaced by increased irritability and increased restlessness.

Social phobia

There are no prevalence studies or specific discussion of diagnostic issues the authors could find that com-ment directly on social phobia. Matson () assigned randomly people with mild to moderate ID and social phobia into a behavioural treatment group and a non-treatment group. The treatment group appeared to do significantly better. Chiodo & Maddux ) reported two people with mild ID and social phobia improved with psychological treatments.

Symptoms of social anxiety have been commented upon particularly in people with fragile X. Maes et al. () found up to % of people with fragile X showed shyness, bashfulness or timidity in social sit-uations and around % withdrew or avoided social situations. This group of people did not show signif-icantly more autistic behaviour than a control group of people with ID without autism.

Specific phobia

Novosel () reported that of adult admissions to an institution in Scotland over a -month period were found to have additional psychiatric symp-




toms. Fifty-eight per cent of this group had phobic symptoms of clinical severity, making it the most common symptom reported. Fear of the dark was the most common phobia. Cooper () reported that .% of a sample of a community population aged – years had phobias other than agoraphobia, although this includes people with social phobia. A number of authors have speculated on aetiological factors in the development of phobias in adults with learning disabilities. Deinstitutionalization has been suggested (Lindsay et al. ; Matson ; McNally & Ascher ), as has an increased fre-quency of negative life events in people with ID with a resultant increase in avoidant behaviour (Hurley & Sovner ). Little has been written on the diagnosis of specific phobias in adults with ID or with difficul-ties in the diagnostic criteria developed for the general population in this group, most of the literature being case reports or short series. However, Jackson () in his review of treatment of phobias in people with ID does summarize assessments used prior to and during treatments. He suggests that measures should be taken in motor-behavioural responses, cognitive-verbal responses and physiological responses. Most commonly used for the former is direct observation, or the Behaviour Approach Test, in which subjects are given instructions to approach the feared stimulus progressively and measures are taken as to how suc-cessful they are. Although he comments on how stan-dardized attitude measures such as the Fear Survey Schedules (Wolpe & Lang ) are useful and appropriate in people with ID, he does not address the difficulties of assessing cognitive responses in peo-ple with more severe ID. He suggests the use of electrodermal and cardiac rate measurements for the assessment of physiological responses. He comments on the usefulness of the clinical interview with infor-mants and notes that case reports and studies rarely use all such desirable measures.

There have been a number of case reports of spe-cific phobias in adults with learning disabilities. Although aspects of diagnosis are rarely discussed, all have in common the need for in vivo contact desen-sitization as an element in the treatment of these phobias. Dog phobia has been described by Jackson & Hooper (), Lindsay et al. (), Erfanian & Miltenberger () and Freeman (). Mansdorf () and Perry () describe cases who had pho-bias of travelling in cars, the latter in a woman with

severe ID who was non-verbal and in whom the diag-nosis was made by observing distress and autonomic features of anxiety, such as hyperventilation, restless-ness, pallor and vomiting. Cases of phobia of heights (acrophobia) have been treated with contact desensi-tization (Spencer & Conrad ; Guralnick ). The latter case was unusual in that imaginal desen-sitization was also used, together with positive rein-forcement. Waranch et al. () described a phobia to mannequins, treated successfully by contact desensitization followed by in vivo exposure in a shopping mall. As with agoraphobia, DC-LD has adapted ICD- diagnostic criteria to include readily observable features of anxiety and has replaced conceptually complex phenomena with additional observable features of anxiety. In none of the diag-nostic criteria for phobias in DC-LD is the individual expected to be able to recognize that the fear is unrea-sonable and excessive, as in ICD-, because this requires a level of intellectual functioning and com-munication which would preclude the diagnosis in individuals with more severe leaning disabilities. Instead, other psychiatric disorders as causes for the fears must be excluded.

Panic disorder

Only two case reports could be found that mention panic disorder directly. Malloy et al. () describe a case of a person with mild ID whose symptoms of panic disorder were missed by clinicians until a struc-tured questionnaire was administered which was adapted from the Structured Clinical Interview for DSM-III-R (SCID) (Spitzer et al. ). The authors make the point that the patient was unable to com-municate the level of her somatic symptoms. More reliance on behavioural observation as recommended by DC-LD would probably been helpful in making the diagnosis sooner.

Khreim & Mikkelsen () reported on the case of a person with mild ID and panic disorder who responded well to sertraline, clonazepam and cogni-tive therapy. They make the point that the internal subjective experience (panic sensations and feelings) can be difficult to perceive and puzzling to people with learning disabilities. DC-LD has addressed this by removing the more complex conceptual phenom-ena such as depersonalization/derealization that are included in the list of symptoms in ICD- and




replacing them by increased irritability and increased restlessness.

GAD

The only information about clearly diagnosed GAD comes from case reports. Ratey et al. () describe a series of eight people with a diagnosis of GAD and ID, all of whom appeared to respond to buspirone at doses between and mg per day. Unfortunately the group all had multiple psychiatric diagnoses apart from GAD. These included alcohol, panic, autism, organic brain syndrome, depression and bipolar dis-order. Ratey et al. () reported on six people who were stated to have an ID. Four people were diag-nosed as having GAD and two people with organic anxiety disorder (OAD). All the individuals with GAD showed reduced anxiety ratings following treatment with buspirone. One person with OAD responded to buspirone. The authors postulated that in brains with low levels of -HT activity, low levels of buspirone may act as a -HT agonist. Ellison () reports one case of a person with severe ID and a diagnosis of GAD panic disorder and agora-phobia who appeared well controlled on imipramine and alprazolam, but improved when buspirone was added and also benefited from desensitization and compliance training.

Khreim & Mikkelsen () describe one case of a person with moderate ID and GAD who responded well to buspirone and cognitive therapy. As with other anxiety disorders DC-LD simplifies some of the more complex conceptual items, making diagnosis easier. Khreim & Mikkelsen () make the point that the excessive and uncontrollable worry of GAD may have a different presentation in people with ID similar to children matched for their developmental age.

OCD

OCD is said to have a prevalence of .% in an institutionalized population of adults with ID (Vitiello et al. ). There are frequent references in the literature to the difficulties in diagnosing this condition in people with ID, due to dependence of criteria in used in the general population on the pres-ence of obsessions (Bodfish et al. a; Khreim & Mikkelsen ) which people with ID find difficult to describe, due to their level of cognitive functioning and difficulties in communication (Bodfish & Madi-

son ). However, it is widely noted that compul-sions are a readily observable phenomenon in people with ID and therefore the observation of their pres-ence by others should allow the diagnosis to be made (Vitiello et al. ; Bodfish & Madison ; Bodfish et al. a; Barak et al. ; Khreim & Mikkelsen ). The reliance on the cognitively complex con-cepts of egodystonicity (recognition of the excessive or unreasonable nature of the thought or motor act) for the diagnosis of OCD in general population cri-teria have also been commented upon (Barak et al. ; Middleton & Cooper ; McNally & Calamari ). Similarly, the cognitive phenomenon of resistance (attempts to suppress, ignore or neutral-ize the thought or motor act) has been described as being difficult to elicit, whether due to its complex nature or difficulties in communication experienced by adults with ID (Vitiello et al. ; Bodfish et al. a; McNally & Calamari ). However, the presence of observable signs of mounting anxiety or tension (often manifesting as aggression to self, oth-ers or property) when compulsions are interrupted or prevented is often evident in adults with ID (Vitiello et al. ; Gedye ; Khreim & Mikkelsen ; Middleton & Cooper ). King () puts for-ward a hypothesis that some self-injurious behaviour seen in people with severe and profound ID may be compulsive in nature.

In view of the difficulties with the International Classification of Diseases [ICD] (World Health Organization ) or Diagnostic and Statistical Manual of Mental Disorders [DSM] (American Psy-chiatric Association ) some authors have stated that general population criteria have been met, but with riders such as with ‘emphasis placed on behav-ioral and observable features of the disorder rather than psychic components’ (Prasher & Day ) or ‘emphasis placed on the objective, observable behav-ior and practical daily consequences, rather than inner conflict and anxiety’ (Vitiello et al. ). Gedye () modified the DSM-III-R (American Psychiatric Association ) criteria for the diagno-sis of OCD by stating that ‘recognition of the behav-iour as excessive or unreasonable may not be true for young children or “those with mental ages of young children” and by stating the compulsive behaviour designed to . . . prevent discomfort “or seems to pro-vide temporary comfort” . . . or it is clearly excessive (modifications in quote marks)’. Gedye () com-




ments that rating scales developed for use in the general population are inappropriate for people with learning disabilities. She developed a compulsive behaviour checklist of types of compulsions grouped into five categories: ordering, completeness/incompleteness, cleaning up/tidiness, checking/touching and deviant grooming. The checklist also includes four items relating to interference with daily living and four items relating to interruption of com-pulsions by others on a four-point scale. The checklist was studied in adults who were known to meet modified DSM-III-R criteria for OCD, but this study did not include any measure of reliability. It was studied subsequently in a proportion of subjects in a study investigating the phenomenological difference between compulsions and stereotypies (Bodfish et al. a) and shown to have over % occurrence agreements on inter-rater, test–retest and validity measures. Similarly, Bodfish & Madison () developed the following criteria in their open treat-ment trial of fluoxetine for what they termed com-pulsive behaviour disorder (rather than OCD): (a) observed to engage in one or more compulsive behav-iours (e.g. ordering, hoarding, touching, checking, cleaning, arranging); (b) had a compulsion that staff members reported interfered to some extent with training and socialization efforts; and (c) were resis-tant to change/novelty. It would appear from the description in the text that there were no exclusion clauses such as the symptoms not being better accounted for by depressive episode or autism. Of the adults fulfilling their diagnostic criteria included in the trial all had self-injurious behaviour or aggres-sion as their prime target behaviours, and all but two had additional stereotypies. Barak et al. () in an open trial of clomipramine in adults with ID, mod-ified DSM-IV (American Psychiatric Association ) criteria by waiving the cognitive component of the description of compulsions and using the specifier of poor insight from DSM-IV, as the subjects did not recognize their compulsions as being excessive. Clearly, the situation where different researchers are adapting existing criteria or creating new criteria in different ways is far from ideal, as difficulties arise in making comparisons between different studies. DC-LD attempts to remedy this by taking the above points into consideration. It does not require a sub-jective description of the thoughts/acts originating in the mind of the individual, but rather that there is no

evidence of the individual believing them to be imposed from an external source. Neither is the indi-vidual expected to be able to recognize that the thoughts/acts are unreasonable, but that they are con-sidered to be repetitive and excessive to observers if not to the individual himself. There is no requirement that resistance to the thoughts/acts is described. An observable feature is added to the DC-LD criteria which does not appear in ICD-, i.e. distress occurs if attempts are made to prevent the individual from carrying out the compulsion.

Other difficulties in detecting and diagnosing OCD in adults with ID have been raised in the literature. First, difficulties in distinguishing compulsions from stereotypies and tics and secondly, differentiating OCD from autism in this population have been described. According to DSM-IV (American Psychi-atric Association ) stereotypies are repetitive, seemingly driven and non-functional motor behav-iours. They are common in people with ID, particu-larly in the severe and profound range of disabilities, and are also seen in autism. There have been several studies in the United States investigating the differ-ences between these phenomena in people with ID. Vitiello et al. () studied all patients with mild to profound ID at a residential facility. Ten were found to have compulsions based on DSM-III-R (American Psychiatric Association ) and these were com-pared with two control groups, one with repetitive non-compulsive behaviour which scored highly on a standardized scale of stereotypy and one which scored low on the same scale. Two independent psychiatrists unfamiliar with the patients rated repetitive behaviour as either compulsion, stereotypy or neither. Inter-rater reliability of the differential classification of com-pulsions vs. stereotypies vs. neither were good (k = .), indicating that the psychiatrists were able to distinguish reliably between these phenomena. Bod-fish et al. (a) carried out an observational study of adults with severe to profound ID living in a state residential facility. They used the Compulsive Behaviour Checklist (Gedye ), and symptom checklists for stereotypy and self injurious behaviour. There was found to be good inter-rater reliability, test–retest reliability and validity on these measures (mean percentage occurrence agreements of over %). Forty per cent of the subjects were identified as displaying compulsions (although this is not equiv-alent to the diagnosis of OCD as information on




severity, frequency and interference on functioning was not collected), .% stereotypy and .% self-injury. They found that comorbidity of compulsions with stereotypies and self-injury was common. They conclude that although all three symptom categories are repetitive, they involved topographically distinct motor movements. Moreover, the majority of subjects manifested more than one movement within a partic-ular category.

In another study carried out by Bodfish et al. (b), it is suggested that there is further indirect neurochemical difference between stereotypies and compulsions. In this study, spontaneous blink rate was recorded as a measure of central dopamine func-tion and compared across three groups: subjects with body-rocking stereotypy, with compulsions and with neither stereotypies or compulsions. The stereotypy group had a significantly lower blink rate compared with the control group, whereas no signif-icant difference was found between the compulsive group and the control group.

There has been little experimental work on distin-guishing tics from compulsions in people with ID. A tic is an involuntary sudden rapid recurrent non-rhythmic stereotyped motor movement or vocaliza-tion (ICD-). Such difficulties in distinguishing these phenomena were raised by Nelson & Pribor () in their case description of a calendar savant with autism and Tourette’s syndrome. King () also raises the issue, stating that it is difficult to oper-ationalize measures of compulsivity in a non-verbal population and gives the example that the behaviour-hopping could be either a ‘simple compulsion’ or a ‘complex tic’. Given the reported comorbidity of obsessive compulsive symptoms in Tourette’s syn-drome (Eapen et al. ), these difficulties may not be easy to resolve, particularly in the ID population.

Differentiating between autism and OCD in people with autism is seen by some as being difficult. Fitzgerald (), in a review article on the differen-tial diagnosis of adolescent and adult pervasive devel-opmental/autism spectrum disorders in general, rather than in the ID population, suggests that autism may be confused with OCD because of the restricted interests, rigidity and desire for the preservation of sameness seen in autism. Bodfish & Madison (), in their open treatment trial of fluoxetine in adults with ID and what they term ‘compulsive behaviour disorder’, include resistance to change/novelty as one

of their criteria for OCD and comment that although these criteria overlap with those of autism, the diag-nosis of autism is ‘too nebulous to reliably guide drug treatment decisions’, implying that their subjects may comprise a subgroup of people with autism. Cook et al. () ask whether the rituals displayed by autistic and other people with ID should be viewed as intrin-sic to their disorders, as secondary adaptations or as evidence for coexisting OCD. Of course, ‘restricted, repetitive and stereotyped patterns of behaviour, interests and activities’ (ICD-) (World Health Organization ) are only one of the three core features necessary for the diagnosis of autism, a point emphasized by Middleton & Cooper (). In addi-tion, ‘qualitative abnormalities in reciprocal social interaction and qualitative abnormalities in commu-nication’ are required. They suggest that OCD is under-diagnosed in adults with learning disabilities due to the inappropriate use of the term ‘autistic traits’ to refer to a person with obsessions or compul-sions but no other autistic symptom. They comment that the use of such a term would not be considered in a person of average intelligence in the absence of the other features of autism. Differences in the phe-nomenology of obsession/compulsions between OCD and autism have also been reported. McDougle et al. () compared adults with autistic disorder seen at a pervasive developmental disorder clinic with adults with OCD seen at an OCD clinic matched for age and sex in a case–control study. The mean IQ of the autistic group was . and % were said to meet DSM-IV (American Psychiatric Association ) criteria for mental retardation, although it would seem there was a bias toward the mild ID/borderline intellectual functioning to account for this. In comparison, although IQ was not measured in the OCD group, none was said to have mental retarda-tion or borderline intellectual functioning. Using direct discrimination function analysis, they showed that autistic patients were significantly less likely to experience thoughts with aggressive, contamination, sexual religious, symmetry and somatic content than patients with OCD. Repetitive ordering, hoarding, telling or asking, touching, tapping or rubbing and self-damaging behaviour occurred significantly more frequently in the autistic group, whereas cleaning, checking and counting behaviour was less common in the autistic group compared with the OCD group. They concluded that the types of repetitive thoughts




are significantly different between autism and OCD. However, as the two groups were not matched for IQ it is not possible to say whether the difference is due to differences in intellectual disability or related to the presence of autism per se. This study requires repeating using IQ-matched controls to determine this.

It is possible, however, to draw some conclusions on the content of compulsions from the studies described above by investigating stereotypies and compulsions in people ID (Vitiello et al. ; Bod-fish et al. a). Ordering has been found to be most common compulsion in both these studies and order-ing and tidiness was also found to be the most fre-quent compulsion in a sample of adults with OCD and Down’s syndrome (Prasher & Day ). In the paper by Bodfish et al. (a), ordering was followed in order of frequency by cleaning, checking/touching, completeness and grooming. However, Prasher & Day () comment that hand-washing, checking and cleaning were rarely seen and Vitiello et al. () found no one in their sample with hand-washing, despite this being the most common compulsion in the general population. It would appear, therefore, that there is probably a difference in the content of compulsions in adults with ID compared with adults of average intelligence.

Conclusions

It is possible to conclude from this review that anxiety disorders do exist in adults with ID and a wide range of such disorders have been described in the litera-ture. There has been widespread comment on the difficulties of using diagnostic criteria developed for the general population with adults with ID. It is dif-ficult to form any firm conclusions as to the preva-lence of specific anxiety disorders, although this relates in part to the lack of appropriate diagnostic criteria for use in this population, and therefore the lack of consistency in diagnosis between studies. While data concerning occurrence of symptoms are common, studies that look at clear diagnostic catego-ries are much more rare. Anxiety is a normal phe-nomenon and indeed is an adaptive response to the many threats we face through our lives. There can therefore sometimes be difficulties in deciding what is pathological anxiety in any given person. This dif-ficulty is compounded in adults with ID who may

have limited abilities to describe complex internal states and in whom there is often some reliance on the report of others. The experience of life of people with ID may be very different from that of those people who care for them, and hence drawing con-clusions as to what is pathological or adaptive can pose a dilemma. This is complicated further when concepts such as developmental appropriateness are taken in to consideration. From the studies reviewed it would appear that, unsurprisingly, fears of adults with ID are similar to those reported by children of equivalent developmental age. Should such fears therefore be considered normal rather than diag-nosed as an additional phobia? Clearly, in any indi-vidual case, there has to be an assessment of the both the content and the severity of the symptoms and signs, as would occur in children of average intelli-gence, before this decision can be made. An assess-ment of the impact on social functioning would play a key role in this.

It has long been shown that additional psychiatric disorders tend to be overlooked in people with ID, and some of the literature on diagnostic overshadow-ing which refers to anxiety disorders has been reviewed here. The under-recognition and hence under-treatment of anxiety disorders in adults with ID results in unnecessary suffering for the individual concerned and also hampers the development of an accurate research basis on which the treatment of such disorders can be studied effectively. It is hoped that the publication of DC-LD (Royal College of Psychiatrists ) as a diagnostic system, based on a consensus of current clinical practice and opinion in the United Kingdom and Republic of Ireland, will assist in diagnosis of anxiety disorders both in clinical situations and in research settings.

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