Department of Psychology, Institute of Psychiatry, King's College London, UK
Department of Psychology and Department of Psychological Medicine, Institute of Psychiatry, King's College London, UK
Department of Psychology, Institute of Psychiatry, King's College London, UK
Department of Psychological Medicine, Institute of Psychiatry, King's College London, UK
Correspondence: Ms Ailsa J. Russell, Department of Psychology, Institute of Psychiatry, PO Box 77, De Crespigny Park, Denmark Hill, London SE5 8AF. Tel: 020 7848 0655; fax: 020 7848 5006; e-mail: a.russell{at}iop.kcl.ac.uk
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ABSTRACT |
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Aim To make such a comparison.
Method A group of adults with high-functioning ASD (n=40) were administered the Yale-Brown Obsessive-Compulsive Scale and Symptom Checklist and their symptoms compared with a gender-matched group of adults with a primary diagnosis of OCD (n=45). OCD symptoms were carefully distinguished from stereotypic behaviours and interests usually displayed by those with ASD.
Results The two groups had similar frequencies of obsessive-compulsive symptoms, with only somatic obsessions and repeating rituals being more common in the OCD group. The OCD group had higher obsessive-compulsive symptom severity ratings but up to 50% of the ASD group reported at least moderate levels of interference from their symptoms.
Conclusions Obsessions and compulsions are both common in adults with high-functioning ASD and are associated with significant levels of distress.
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INTRODUCTION |
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METHOD |
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Consecutive referrals to specialist autism services at the Maudsley Hospital in south London were approached about participating in the study. A diagnosis of ASD was determined using ICD-10 criteria (World Health Organization, 1992) for autism and Asperger syndrome. In addition, where parents were available (23 cases, 58%) the Autism Diagnostic Interview (ADI; Le Couteur et al, 1989) was conducted. Of the adults with ASD, 36 (90%) were diagnosed with Asperger syndrome and 4 (10%) with high-functioning autism, with significant delay in the acquisition of spoken language delineating the latter according to ADI criteria. Each individual was subject to careful diagnostic assessment by a consultant psychiatrist specialising in ASD, and ICD-10 comorbid diagnoses were recorded in the admission and/or discharge medical reports. Mean Verbal and Performance IQs on the Wechsler Adult Intelligence Scale - third edition (WAIS-III; Wechsler, 1981) for the ASD group were 99.18 (s.d.=18.37) and 93.68 (s.d.=13.13), respectively. Participants with OCD were recruited from a specialist clinic in west London. All were diagnosed using semi-structured interviews by experienced clinicians using DSM-IV (American Psychiatric Association, 1994) or ICD-10 criteria.
Severity and types of OCD symptoms
The severity and types of obsessive-compulsive symptoms were measured
using, respectively, the ten-item Yale-Brown Obsessive-Compulsive Scale
(Y-BOCS) (Goodman et al,
1989) and its ancillary Symptom Checklist (Y-BOCS-SC). The
Y-BOCS-SC is a list of more than 50 examples of obsessions and compulsions
grouped thematically into seven main groups of obsessions and six of
compulsions. A score of 0 (absent symptom) or 1 (present symptom) was given to
each of the 13 main types of obsessions and compulsions. Miscellaneous
obsessions and compulsions were not included in the analyses, as they contain
many different types of symptoms that do not naturally cluster together.
For the purpose of this study it was important that only genuine obsessions and compulsions were recorded in the Y-BOCS-SC, and an effort was made to distinguish those from the stereotypic behaviours and interests usually displayed by people with ASD. At the beginning of the interview, each ASD participant was asked what was meant by an obsession. Participants who offered a definition consistent with an obsessive-compulsive symptom were prompted to report any similar experiences they had before the Y-BOCS-SC was administered. If a participant defined an obsession as something one is very interested in, the examiner agreed that this could be so, but explained that the interview was about another type of obsession; a definition was then offered and the participant was again prompted to report their own experiences. If the participant did not have any obsessions or did not understand the question, an example of a typical obsessive-compulsive symptom was offered. This procedure was repeated for compulsions. Symptoms were only rated if they caused some degree of discomfort and interfered with the patient's daily life. Two raters independently scored the Y-BOCS-SC in a subsample of the ASD group (n=4) and consensus reliability for the symptom checklist and the severity scale was established. Interrater agreement was calculated as an overall percentage of items where both observers agreed, divided by the total number of items. A high level of agreement was achieved.
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RESULTS |
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Comorbid ICD-10 diagnoses in the ASD group were not available for 3 (7.5%) patients. Seventeen (42.5%) patients did not receive an additional psychiatric diagnosis. Of the 20 (50%) participants with comorbid diagnoses, 11 (27.5%) received a diagnosis of affective disorder, 10 (25%) were diagnosed with comorbid OCD, 3 (7.5%) had a discharge diagnosis of schizophrenia and 4 (10%) had an anxiety disorder other than OCD.
Types of obsessive-compulsive symptoms
A similar frequency of obsessions and compulsions was observed across the
two groups (Table 1). The OCD
group did, however, report significantly higher frequencies of somatic
obsessions and repeating and checking compulsions. A discriminant function
analysis (stepwise procedure) showed that group membership was best predicted
on the basis of a single type of obsession, somatic obsessions
(F=15.845, d.f.=1,83, P<0.0001), and a single type of
compulsion, repeating compulsions (F=10.460, d.f.=2,82,
P<0.0001). Both were more frequent in the OCD group. None of the
other symptoms improved the fit of the model or were retained in the
analysis.
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The analyses were repeated comparing the symptom types endorsed by the
group with ASD plus a formal diagnosis of OCD (n=10) with those
endorsed by the OCD group. Somatic obsessions were significantly more frequent
in the group with OCD alone (2=6.19, d.f.=1,
P=0.013), with (10%) of patients in the ASD plus OCD group endorsing
this symptom type compared with 24 (53%) patients in the OCD group. Sexual
obsessions were more commonly reported by patients in the ASD plus OCD group
(
2=3.9, d.f.=1, P=0.046), with 7 (70%) of the group
endorsing this symptom type compared with 16 (36%) of the OCD group. A
discriminant function analysis (stepwise procedure) showed that group
membership was best predicted by somatic obsessions (F=6.730,
d.f.=1,53, P<0.01) and sexual obsessions (F=7.650,
d.f.=2,52, P<0.001). No other variables were retained in the
analysis.
Number of endorsed symptoms
The OCD group reported a mean of 10.4 (s.d.=7.4) obsessions and 7.8
(s.d.=4.54) compulsions compared with a mean of 6.7 (s.d.=5.36) obsessions
(t=2.609, d.f.=83, P=0.001), and 4.4 (s.d.=4.1) compulsions
(t=3.561, d.f.=83, P=0.001) in the ASD group.
Symptom severity
Y-BOCS severity scores were available for 38 participants with ASD and 44
with OCD. As predicted, the OCD group scored significantly higher on the
Y-BOCS total scales (OCD mean=23.8, s.d.=7.1, ASD mean=16.2, s.d.=9.7;
t=4.1, d.f.=81, P<0.001), obsessions (OCD mean=11.6,
s.d.=3.9; ASD mean=8.46, s.d.=6.1; t=2.8, d.f.=79, P=0.005)
and compulsions (OCD mean=12.09, s.d.=3.9; ASD mean=7.6, s.d.=5.3;
t=4.3, d.f.=80, P<0.0001).
Breakdown of the Y-BOCS items in the ASD group revealed that 15 (39%) rated the time taken by their obsessions to be moderate (1-3 h/day) or above; 18 (47%) reported at least moderate levels of interference and 23 (60%) reported at least moderate levels of distress as a result of their obsessions. Compulsions occupied at least 1-3 h/day in 12 (26%) of the group with ASD; these led to moderate or above levels of interference in 16 (42%), and 21 (56%) reported at least moderate levels of anxiety if prevented from performing their rituals.
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DISCUSSION |
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In the only previous study investigating obsessive and compulsive symptoms in ASD (McDougle et al, 1995), particpants with ASD and OCD were distinguished by seven types of repetitive thoughts and behaviours, with the latter being predominant. The authors postulated that this could be accounted for by the below average general IQ and verbal abilities of the ASD group; our findings support this.
It is intriguing that somatic obsessions were much more frequent in the OCD group than in the ASD group and even in the ASD plus OCD group. There is minimal literature on the identification and reporting of physical health problems in ASD. However, it is a common clinical observation and families often report that these individuals have difficulties reporting any physical complaints; instead increased agitation/behavioural disturbance and distress may be seen. In the Autism Diagnostic Interview - Revised (ADI-R; Lord et al, 1994), lack of reporting and seeking comfort following physical illness and injury is an important diagnostic feature of a pervasive developmental disorder during childhood. Lack of focus on internal physiological discomfort would appear to directly translate into a lack of focus for anxiety in this group.
Implications
These results may have important implications for both clinical practice
and research. From a therapeutic perspective, clinicians need to consider the
possibility of significant obsessive-compulsive symptoms in ASD, rather than
classifying repetitive phenomenology as characteristic of ASD. Proper
assessment to distinguish these two types of phenomena is important.
Additionally, individuals with ASD who have distressing levels of obsessive-compulsive symptoms may benefit from standard treatments for OCD such as serotonin reuptake inhibitors (McDougle et al, 2000) and cognitive and behavioural therapies (Marks, 2003), but controlled trials are needed to evaluate the efficacy of these interventions in ASD. Executive function deficits and a preference for local rather than global information processing have been reported in both ASD and OCD (Ozonoff et al, 1991; Savage et al, 1999). However, it is not known whether obsessive-compulsive behaviours in OCD and ASD share a common neural basis. We hope that the current results will stimulate research in these areas.
Obsessional thoughts are not in themselves uncommon and have been reported by 80% of the general population (Rachman & De Silva, 1978). The cognitive style and deficits that have been empirically associated with ASD (Happe, 1994) may influence the way in which these normal phenomena are appraised. High levels of general anxiety are typical in ASD, and this may also modulate the evolution of obsessive-compulsive symptoms.
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Clinical Implications and Limitations |
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LIMITATIONS
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REFERENCES |
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Received for publication February 24, 2004. Revision received September 14, 2004. Accepted for publication October 30, 2004.
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