Whichever way you look at it and whatever you think causes it, autism is a complex phenomenon. So it isn’t surprising that different researchers have different conceptual models of how autistic characteristics and their causes are related. Different conceptual models might confuse the public, but researchers are generally well aware of what other researchers think and why. But confusion can arise when conceptual models appear similar but are subtly different.
Here’s Mary Coleman in an interview with Adam Feinstein: “I came to realize that autism is like mental retardation – it’s a final common pathway in the brain affected by many different underlying causes, many different disease entities.” (p.147).
Feinstein says Coleman is ‘convinced that autism will eventually be found to consist of dozens – possibly hundreds – of different subtypes, each the result of a specific medical condition. She told me: “I’m not talking about co-morbidity. I’m talking about the basic disease which causes the autistic symptoms.”’ (p.194)
Now Isabelle Rapin, also interviewed by Feinstein:
“Autism is a behavioural, not a medical diagnosis…I agree entirely with the concept of autism as a disorder of the developing brain. What I emphasize is that autism is defined behaviourally, in the same sense that dementia is behaviourally defined…but is, of course, medically caused. There… is no single cause, but many. I disagree with the idea that autism is a ‘disease’ – in the sense that it has one defined cause. I have always believed it reflects dysfunction of particular circuitry in the brain, whatever the biological cause of the dysfunction.” (p 194)
Thomas Kemper, who with Margaret Bauman carried out some pioneering studies of brain development in autism, says;
“I still think there’s a unifying feature or group of features about children with autism: the way they use language, the way they interact socially, their play skills. There is a key group of features. I accept that it is a spectrum. But we should still be hunting for what is similar, the unifying characteristic. Even if Mary Coleman refers to 70 different kinds of autism, she’s still calling it autism. There may be different ways of getting there, but I’m not ready to give up on the hunt for some core, unifying feature of the brains of children with autism.” (p. 210)
It seems to me that each of the above researchers subscribes to essentially the same ‘fan-in/fan-out’ model; that many different biological causes can produce impairments in a final common pathway that varies widely in its manifestations. Each has a different but important emphasis. Coleman emphasises the differences between the causal disease entities; Rapin the distinction between behavioural characteristics and their biological causes; and Kemper the similarities in behaviour between children.
The term ‘autism’ is a construct that refers to a triad of types of symptom. Whether that maps on to a single ‘thing’ in the real word remains to be seen, but it’s not safe to assume that it does. Jon Brock has addressed this point elegantly in his blog here.
What I find intriguing is that each of these researchers subscribes to the idea of a ‘final common pathway’, ‘dysfunction of a particular circuitry in the brain’, ‘some core, unifying feature of the brains of children with autism’. What, if anything, all people diagnosed with autism have in common is a moot point. The issue of what it is they actually have in common is dealt with explicitly by John Morton and Uta Frith in their work on causal modelling. I plan to examine this in more detail in a later post, but for the moment I’ll concentrate on the confusion in conceptual models.
That way confusion lies
It’s bad enough having to take into account subtle differences in the same conceptual model. It gets even more confusing when the same terminology has different meanings. I’ve noted some terms that are each used in different ways in the autism literature.
can refer to either;
autistic characteristics – impairments in social interaction, communication and flexible behaviour
a medical condition assumed to cause autistic characteristics.
Using the same label for both is like diagnosing patients with a sore throat, rash and fever as having ‘sore-throat-rash-and-fever disorder’. It’s an accurate and valid label – all patients with those symptoms definitely have them – but using that term for both cause and effect wouldn’t make it clear whether you were talking about the symptoms or what causes them. It also implies that all patients have the same cause for their symptoms, when we know that there are many different causes for sore throats, rashes and fevers. In the case of autism the jury is still out on the links between cause and effect, so it’s not safe to assume, implicitly or explicitly, that there is only one underlying cause.
2. disease, illness, disorder, condition
are often used interchangeably.
As far as I can ascertain, the usual technical meanings of these terms are as follows;
disease – an infection that impairs normal function
illness – the patient feels unwell. Patients can have impaired function but not be ill, or be ill but not have impaired function.
disorder – a disruption in normal functioning. Normality is an interesting concept and one I plan to discuss in a later post.
condition – the patient’s state from a medical perspective. The patient doesn’t necessarily have a disease, illness or disorder.
The term ‘autistic spectrum condition’ (ASC) is sometimes used in place of ‘autistic spectrum disorder’ (ASD) because ‘condition’ doesn’t imply there is anything ‘abnormal’ about the person.
3. autism is a disorder with a heterogeneous aetiology
can mean either;
different things cause autistic characteristics in different people
different things cause autistic characteristics in an individual.
This phrase is often found in the introductory sections of research papers, but it’s not always clear what it means. One theory for the origins of autism is that autistic characteristics are triggered by environmental factors if a relevant genetic predisposition is present. It’s possible that several genes might be involved. So the causes of autism within an individual can be heterogeneous. Researchers using the phrase might be saying that different people probably have different causes for their autistic characteristics or might be assuming that every person diagnosed with autism has the same heterogeneous aetiology for their symptoms.
Enough of conceptual models for the moment. Bearing in mind the ambiguities in conceptual models and terminology, I next want to turn my attention to theories about the causes of autism.
Feinstein, A (2010). A History of Autism. Wiley Blackwell.