3.2 Continuum or sub-types?
One interpretation of cases like Asperger's astronomer is that they represent the typical life-span development of an autistic person who, because less intellectually disabled, develops more successful living strategies. Some clinical practitioners use the term High Functioning Autism (HFA) to denote this group, implying that autism is a continuum, spanning individuals with different levels of intellectual and social disability and including individuals with ‘borderline’ autistic symptoms. This might be seen as suggesting, in turn, an ill-defined boundary between ASDs and ‘normality’. In keeping with this, you perhaps know someone who, without having attracted any clinical label, is extremely ‘driven’ in one field, while seeming eccentric and lacking in social graces. Marian Glastonbury (1997) has argued that the unusual life style of prominent writers and philosophers such as Kafka, Beckett and Wittgenstein, coupled with the eccentric genius and prolific nature of their work, is consistent with an autistic type condition.
Whether these examples really demonstrate that autistic spectrum disorders ‘shade’ into normality partly depends on how we define ‘disorder’ and ‘normality’. Some researchers refer increasingly to a broad cognitive phenotype for autism, that is, a distinctive way of engaging with the physical and social world, shaped by both genetic and environmental influences, that only manifests as a disorder in more extreme cases. This fits well with the continuum model.
Other practitioners have argued that the difficulties of individuals such as Asperger's patient are qualitatively distinct from classic autism and constitute a separate sub-type. In the early 1990s, this widespread shift in thinking stimulated the introduction of separate diagnostic criteria for Asperger's syndrome.
The criteria currently proposed for Asperger's syndrome in DSM-IV-TR™ (see Box 1) are identical to those proposed for classic autism in two of three main triad headings: ‘Qualitative impairments in social interaction’ and ‘Restricted repetitive and stereotyped patterns of behaviour, interests and activities’. They differ most significantly in omitting the triad area ‘Qualitative impairments in communication’, suggesting instead that:
There is no clinically significant general delay in language development.
There is no clinically significant delay in cognitive development, in normal everyday skills (other than social ones), or in curiosity about the environment.
Look at the extract from Asperger's account of the astronomer. Do the DSM-IV-TR™ criteria revised as above for Asperger's syndrome match better with the astronomer's difficulties than the original criteria for autism given in Box 1?
In keeping with the Asperger's criteria, the astronomer showed impairments in social interaction, a restricted range of activities and interests, and, arguably, no delay in cognitive development. But he did seem impaired in his communication and everyday skills, had difficulty learning a new language, and was described as extremely clumsy and gauche.
Peeters and Gillberg (1999) point out that contrary to the implications of DSM-IV-TR™, it is extremely rare for any person with autistic spectrum symptoms to have entirely normal use of language. In ‘Asperger type’ autism, expressive language may be grammatically and syntactically perfect, and yet it may be excessively formal and pedantic. Receptive language may be far too literal and concrete, as illustrated by Gunilla Gerland in Section 1. It is typically these pragmatic aspects of language understanding that people with Asperger-type autism seem to find difficult. The omission of communication difficulties from the diagnostic criteria is therefore controversial. Peeters and Gillberg also argue that clumsiness, or lack of motor co-ordination, is a distinctive feature of ‘Asperger type’ autism, and should be included in the diagnostic criteria.
Most clinicians agree that Asperger's syndrome is a recognisable sub-type of autism, yet there is disagreement about what distinguishing features should be enshrined in diagnosis. This is not as surprising as it might seem: diagnostic systems such as DSM-IV-TR™ are constantly revised and updated by expert working groups, in the light of new research and clinical findings.
It might seem that continuum and ‘sub-type’ approaches are contradictory, since one implies a continuous dimension of variation, shading into ‘normality’, while the other assumes clinical entities that are, at least to some extent, discreet from one another and from ‘normality’. In practice both approaches have some validity in different contexts. The continuum approach draws attention to shared features of all ASDs such as social difficulties and preference for a highly structured environment. It is useful to highlight such generic problems for people like teachers who may be encountering people with ASDs for the first time. The ‘sub-type’ approach serves to highlight more specific educational and therapeutic needs of different sub-groups. For instance, children with Asperger's syndrome are typically capable of integrating into a mainstream school, while those with profound autism are more likely to flourish in a specialised educational environment.
Epidemiological study: Large-scale study of the incidence and distribution of a disorder within a population.
High functioning autism: A sub-area of the autistic spectrum, characterised by less severe symptoms and/or higher intellectual level.
Continuum: A dimension of continuous variation, without breaks or discreet steps.
Cognitive phenotype for autism: A distinctive profile of cognitive skills or strategies characteristic of the autistic spectrum that is the outward (phenotypic) expression of genetic attributes (genotype), in interaction with environment.
Asperger's syndrome: A sub-type of autistic spectrum disorder similar or identical to High Functioning Autism. Clinicians disagree about whether it involves language difficulties, and how far it is qualitatively distinct from other autistic spectrum disorders.
Expressive language: Competence in the production of language.
Receptive language: Competence in understanding language produced by others.