The diagnostic boundary between autism spectrum disorder, intellectual developmental disorder and schizophrenia spectrum disorders
| DOI | https://doi.org/10.1108/AMHID-05-2015-0024 |
| Pages | 243-264 |
| Date | 07 September 2015 |
| Published date | 07 September 2015 |
| Author | Marco O. Bertelli,Micaela Piva Merli,Elspeth Bradley,Roberto Keller,Niccolò Varrucciu,Chiara Del Furia,Nicola Panocchia |
| Subject Matter | Health & social care,Learning & intellectual disabilities |
The diagnostic boundary between autism
spectrum disorder, intellectual
developmental disorder and
schizophrenia spectrum disorders
Marco O. Bertelli, Micaela Piva Merli, Elspeth Bradley, Roberto Keller, Niccolò Varrucciu,
Chiara Del Furia and Nicola Panocchia
Dr Marco O. Bertelli is Scientific
Director at CREA (Research and
Clinical Centre), San Sebastiano
Foundation, Florence, Italy and
EAMHID, European Association
for Mental Health in Intellectual
Disability, Florence, Italy.
Dr Micaela Piva Merli is based at
CREA (Research and Clinical
Centre), San Sebastiano
Foundation, Florence, Italy.
Dr Elspeth Bradley is based at
Surrey Place Centre and
Department of Psychiatry,
University of Toronto, Toronto,
Ontario, Canada.
Dr Roberto Keller is based at
Adult Autism Spectrum Disorder
Center, Local Health Unit ASL 2,
Turin, Italy.
Dr Niccolò Varrucciu is
Psychologist-Psychotherapist,
Researcher at CREA (Research
and Clinical Centre), San
Sebastiano Foundation,
Florence, Italy. Dr Chiara Del Furia
is based at CREA (Research and
Clinical Centre), San Sebastiano
Foundation, Florence, Italy.
Dr Nicola Panocchia is based at
the Department of Surgery
Catholic, University of the Sacred
Heart, Roma, Italy.
Abstract
Purpose –During the last few years the prevalence of autism and Autism Spectrum Disorder (ASD) has
increased greatly. A recurring issue is the overlap and boundaries between Intellectual Developmental
Disorder (IDD), ASD and Schizophrenia Spectrum Disorders (SSD). In clinical practice with people with IDD,
the alternative or adjunctive diagnosis of ASD or SSD is particularly challenging. The purpose of this paper is
to define the boundaries and overlapping clinical characteristics of IDD, ASD and SSD; highlight the most
relevant differences in clinical presentation; and provide a clinical framework within which to recognize the
impact of IDD and ASD in the diagnosis of SSD.
Design/methodology/approach –A systematic mapping of the international literature was conducted on
the basis of the following questions: first, what are considered to be core and overlapping aspects of IDD,
ASD and SSD; second, what are the main issues in clinical practice; and third, can key diagnostic flags be
identified to assist in differentiating between the three diagnostic categories?
Findings –Crucial clinical aspects for the differentiation resulted to be age of onset, interest towards others,
main positive symptoms, and anatomical anomalies of the central nervous system. More robust diagnostic
criteria and semeiological references are desirable.
Originality/value –The present literature mapping provides a comprehensive description of the most
relevant differences in the clinical presentation of ASD and SSD in persons with IDD.
Keywords Intellectual disability, Dual diagnosis, Autism spectrum, Co-occurrence, Differential diagnosis,
Schizophrenia spectrum
Paper type Literature review
Introduction
In the last decade the prevalence of autism has increased considerably. In the 1960s the most
reported rate was 0.5/1.000, while currently it reaches 1-2/1,000 (Newschaffer et al., 2007).
Additionally Autism Spectrum Disorder (ASD; APA, 2013) has increasingly been reported to have
a high prevalence and are now considered the most common group of disorders in childhood,
with a prevalence of 6/1.000 (Newschaffer et al., 2007; Fombonne, 2009). A 2009 American
report (Boseley, 2009) based on the 2007 Adult Psychiatric Morbidity Survey by the National
Health Service, UK determined that the prevalence of ASD in adults is approximately 1/100
(Brugha et al., 2011). Such rapid and significant increase in prevalence estimates raises a
number of questions as to the origins of this increase (Weintraub, 2011; Hughes, 2012), whether
Received 20 May 2015
Revised 20 May 2015
Accepted 2 July 2015
DOI 10.1108/AMHID-05-2015-0024 VOL. 9 NO. 5 2015, pp. 243-264, © Emerald Group Publishing Limited, ISSN 2044-1282
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ADVANCESIN MENTAL HEALTH AND INTELLECTUALD ISABILITIES
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this is due to changes in diagnostic procedure and criteria interpretation (Fombonne, 2009; Wing
and Potter, 2002; Gernsbacher, 2005; Wazana, 2007) or due to spontaneous epidemiological
phenomenon (Rutter, 2005; Szpir, 2006).
True increase in prevalence
Factors that could have played a role in this prevalence increase include growing awareness and
changes in referral patterns, changes in diagnostic criteria, in particular the development of the
concept of the wider autistic spectrum and different diagnostic methods used in studies
(Fombonne, 2009; Wing and Potter, 2002; Matson and Kozlowski, 2011).Various environmental
causes for a real rise have been suggested, including the triple vaccine for measles, mumps and
rubella. Not one of the possible environmental causes has been confirmed (Wing and Potter,
2002; Rutter, 2005) whereas there is strong evidence that complex genetic factors play a major
role in etiology. Indeed family studies show early markers (Shoubridge et al., 2010; Noor et al.,
2010; Tarpey et al., 2009) and define a broader autism phenotype than described by Kanner
(Kanner, 1973; Fisch et al., 2011; Georgiades et al., 2011; Ching et al., 2010).
Growing awareness and changes in referral patterns
Others factors that could have played a role in increased prevalence estimates are growing
awareness and knowledge among the general public, parents and professional workers and the
development and availability of specialist services (Fombonne, 2009; Wing and Potter, 2002;
Matson and Kozlowski, 2011). Since the 1960s there has been greater general interest in autism
including the development of parent voluntary associations that have pushed for educational and
treatmentservices for their children as well as encouragedresearch in the area. These associations
have been energeticin ensuring publicity concerning the needs of their family members with ASD
through all the media. Professional interest has stimulated scientific investigation into autism. For
example in 1999 the number of published epidemiological studies on autism is reported as 23,
rising to 32 in 2003 (Fombonne, 2003) and to 53 in 2009 (Fombonne, 2009).
Moreover since the late 1970s the numbers of institutions and schools for people with mental
retardation (MR)have gradually diminished. On the other hand,all kinds of specialist services such
as family support, schools for children and adults with autistic disorders have been developed
(Wing, 2001). As a consequence professionals may be more willing to make a diagnosis of an
autistic condition if they know that it will lead to appropriate help (Matson and Kozlowski, 2011).
Definitions and changes in diagnostic criteria –development of the spectrum concept
Since the 1960-1970s there has been controversy around the definition of autism. In the 1980s
the discrepancy between the international nosographical systems was still evident. The ICD-9
considered autism as a sub-category of schizophrenia, with onset in the childhood, while the
DSM-III included autism and related conditions in the field of ASD (APA, 1980). The ASD
spectrum has gradually expanded to include milder clinical forms and frequently associated with
other diseases or health-related conditions (Lenoir et al., 2009; Charman, 2002). In DSM-IV (APA,
1994) the diagnostic subcategories were extended to two new conditions: Asperger syndrome
and ASD-NOS (not otherwise specified). ASD-NOS were defined by subthreshold symptoms,
too mild to make a diagnosis of real autism. The ICD-10 adopted this new tendency. The addition
of these two categories (Asperger syndrome and ASD-NOS) has significantly contributed to the
increase in the number of autism diagnoses. The just published DSM-5 combines the four
previously separate disorders into a single condition with different levels of symptom severity in
two core domains: first, deficits in social communication and social interaction; and second,
restricted repetitive behaviours (RRBs), interests, and activities (Achkova and Manolova, 2014).
Because both components are required for diagnosis of ASD, social communication disorder is
diagnosed if no RRBs are present (APA, 2013). The DSM-5 working group also considered that
symptoms must be present in early childhood but may not become fully manifest until social
demands exceed limited capacities. One criticism of DSM-IV and DSM-5 is that they are
responsible for widening of the criteria for autism spectrum conditions, thus leading to a
progressive increase in published prevalence rates (Wing et al., 2011).
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