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Dr Elisabeth Hill (Senior Lecturer in Psychology at Goldsmiths University of London)

Understanding the autism spectrum

By Dr Elisabeth Hill (Senior Lecturer in Psychology at Goldsmiths University of London)

This article forms part of a School Resource Pack created by the Progress Educational Trust (PET) as part of its project Spectrum of Opinion: Genes. The article incorporates links to an accompanying Glossary of terms, and is followed by a list of 10 key words, phrases and names and a set of Questions to consider. A more extensive version of the article can be found on PET's BioNews website.

It is important that we search for the cause(s) of autism spectrum disorder, in order to improve support, education and employment for people on the autismspectrum. But there are two problems. First, finding a cause might not be simple or even achievable. Second, there might not be a unitary cause to explain all of the behaviour of a person with autism spectrum disorder.

There is a very varied profile of behaviour observed in autism, both at one measured time point (between individuals) and over the lifespan (within an individual). In order to improve our understanding of the condition, it is important to investigate this varied profile. One useful method, that will improve the chance of studies successfully identifying causes and linking brain and behaviour, is the causal modelling approach to neurodevelopmental disorders.

This approach can be used to model multiple theories of a single disorder (in this case autism spectrum disorder), as well as to model possible similarities and differences between the causes and consequences of different disorders. The model has four constituent parts - biology, cognition, behaviour and the environment. Relationships between these different parts of the model can also be considered.

By considering the cognitive explanations for behaviour observed in autism spectrum disorder, we can start to establish how groups of behaviours link together (implying a common cause), and where other behaviours are separate (implying different causes). This approach enables a visual picture of potential links between the different levels of description of a disorder to be made. This can then help us interpret patterns of behaviour, and carefully investigate their causes.

This approach can help us to identify cognitive endophenotypes - that is, groups of behavioural symptoms with a common cognitive origin - of autism spectrum disorder. Individuals with such groupings of symptoms can then be considered as subgroups, that may be associated with varying causes and consequences. It could be argued that the most obvious subgrouping is the distinction between classical autism and Asperger's syndrome.

There are likely to be multiple causes and consequences of the autism spectrum, and there is no reason to expect that one cause will explain all aspects of the disorder. In fact, recent genetic work suggests that different aspects of the cognitive phenotype are explained by different genetic contributions. We must also look for explanations that might help us understand and explain the behavioural consequences of the condition, as seen in everyday behaviour.

The complexity of the autism spectrum at many levels - cognitive, behavioural and biological - has become increasingly clear in recent years. This complexity is one of the reasons why it is difficult to identify the cause of the condition. Another reason is that different research methods are isolated from each other. We need a more integrated approach, where different methods as well as comparison groups are combined within the same study.

It is also important that everyone involved in improving and supporting the lives of those affected by autism spectrum disorder appreciates the level of detail and time that the search for a cause will consume. Research that may not appear to address the causes of autism directly may, in the longer-term, prove to be hugely beneficial. If funding is provided only for research that appears to have a direct focus on cause (such as genetic studies), then we will be far slower to make the progress that we would like.

Genetic and other studies are crucial to understanding autism. But while it is important to provide sufficient resources for these studies, it is also important to provide the public with realistic expectations of what scientific techniques can achieve.

    Questions to consider

  1. If in future we have a better understanding of the causes of autism, what difference (if any) will this make to autistic people?

  2. If the causes and consequences of two different disorders overlap with each other, should we consider creating a new definition that combines the two disorders into one?

  3. Why is it important for the public to have realistic expectations of science?