4.0 Possible causes

Early in the 1960's, only a few years after Kanner and Asperger had defined parts of the autistic spectrum, the psychogenic theory of autism gained ground. This theory, now totally unsupported, suggested (with little evidence) that the way parents brought up their children could actually 'cause' autism.

Some even went as far as suggesting those children should be removed from their parents as a part of their treatment.

4.1 Growing knowledge

Later in the 1960's research into the way the brain functioned and the how the process of brain development can go wrong pre- and post-natal started to show that autism was indeed a spectrum of conditions and that they are disorders of development.

4.2 So what causes autism?

Once researchers had dismissed emotional causes for autism (although this is still a belief held in some countries) it became apparent that there must be a biological origin to the disorder. There were a number of powerful indicators for a biological cause:

1. Autism is often accompanied by other neurological symptoms;
2. Autism is often associated with other learning difficulties;
3. Autism is often accompanied by epilepsy;
4. Mothers of autistic people often report difficulties in pregnancy and labour;
5. Other conditions such as viral infections, metabolic conditions and genetic abnormality are closely related to autistic spectrum disorders.

Armed with this theory, researchers were then faced with the prospect of trying to isolate 'the' cause. However, it became apparent very quickly that one single biological cause was unlikely. After all, there are many people with autism who do not have any apparent medical condition likely to have caused the disorder, and who have no learning difficulties and are not epileptic!

However, when studies were made of groups of children with autism, researchers noted that a greater number of certain types of medical conditions were found when compared to groups of children who were not diagnosed as autistic.

Thus the implication was clear � in all cases of people with autism a biological cause lies behind the disorder, although the nature of this cause is only identifiable in a minority of cases.

4.3 What parts of the brain are affected?

Before we look at the potential medical conditions that can lead to autism, it is worth looking at the evidence for neurological abnormalities. It is also important to note that 'brain damage' is an emotive term in itself. Many people with autism look quite ordinary so how is it possible that damage has occurred? The answer is that we don't know, or more precisely we don't know yet. The tools we have available to analyse are relatively crude compared to the immense complexity of the brain.

Nevertheless, brain abnormalities are often found in people with autism and it is assumed that those that do not have observable anomalies are simply outside the range of what today's science can detect.

4.3.1 The evidence

At present, various techniques are used to obtain pictures of the brain including CAT (Computer Axial Tomography) scans and MRI (Magnetic Resonance Imaging) scans. Several studies have revealed abnormalities in different regions of the brain. The following areas have been highlighted for special attention:

1. Abnormalities in the frontal lobes � areas in the brain responsible for planning and control.
2. Abnormalities in the limbic system � the part of the brain responsible for emotional regulation.
3. Abnormalities in the brain stem and fourth ventricle or in the cerebellum � which governs motor coordination.

What all this research shows is that in many cases brain anomalies are associated with people with autism. Brain research has also shown that between 30 and 50% of children with autism have abnormally high levels of serotonin in the blood, a chemical responsible for transmitting signals in nerve cells.

Continued research in these areas will further refine our knowledge of what parts of the brain are affected in people with autism. Let's take one step back and look at what may have caused this damage in the first place.

4.4 Medical conditions that may cause autism

The following lists the medical conditions that have been identified in some children with autism:

• Genetic conditions;
• Viral infections;
• Metabolic conditions; and
• Congenital anomaly syndromes.

4.4.1 Genetic conditions

Studies of identical twins (sharing identical genetic material) and non-identical twins (sharing half their brothers or sisters genes) have shown an increased prevalence of autism in identical rather than non-identical twins. This shows a clear genetic link. However, even with identical twins there are recorded cases of just one sibling with autism.

There are also some rare genetic conditions that sometimes give rise to autism. These include:

• Tuberous sclerosis � a conditions characterised by unusual skin pigmentation, a facial rash and growth of tumours on the brain � commonly leading to autism;
• Fragile X syndrome � one of the commonest causes of autism yet identified � this condition leads to learning difficulties and unusual facial appearance (large ears, long nose and high forehead).

4.4.2 Does autism run in families?

About 2-3% of brothers and sisters also develop autism. This is higher than you would expect by chance, reinforcing the genetic link to the disorder. Likewise it is sometimes seen that another family member say a grandfather or an uncle, behaved oddly, but this had simply been seen as their 'eccentricity'.

4.4.3 Do difficult pregnancies and births cause autism?

The jury is still out on this one. Difficulties in birth are of course responsible for brain damage. However, only in a very small minority of cases does the child develop autism. Also it is reasonable to suggest that the difficulty in birth may be a by-product of the fact that the child already has some form of abnormality.

4.4.4 Infection as a cause of autism

It is rational to assume that if autism has a biological origin, and that origin lies in damage to a certain region of the brain, then a virus which can affect the brain may result in autism. Therefore the following viral illnesses have been linked:

• Rubella � if contracted in the first 3 months of pregnancy the unborn baby's brain can be damaged resulting in a range of problems including autism. However, in many countries vaccination programmes have made this much rarer.
• Herpes encephalitis � this virus can affect infant's brains leading to encephalitis. Children so affected can display an autistic-like condition.

4.5 In summary

As we have seen, much recent research reveals a link between autism and abnormalities in the brain. If the agent of damage affects those regions of the brain responsible for social interaction, social communication and imagination it is possible that the triad of impairment will result and the person will develop the disorder.

However, the exact causes are not known so the notion of a 'final common pathway' has been proposed:

This suggests that a variety of medical conditions can lead to brain damage, and if critical parts of the brain are affected then the individual may display the typical features of autism.