What is autism?

amygdala (red) in brain Individuals with autism have less activity in the amygdala (shown in red), which plays a key role in processing emotions

Autism and Asperger syndrome are part of a range of conditions known as autistic spectrum disorders (ASD). They affect the way the brain processes information.

What is autism?

Autism is a developmental disorder that can cause problems with social interaction, language skills and physical behaviour. People with autism may also be more sensitive to everyday sensory information.

To people with the condition the world can appear chaotic with no clear boundaries, order or meaning.

The disorder varies from mild to so severe that a person may be almost unable to communicate and need round-the-clock care.

Research has revealed that people with autism have brains that function in a number of different ways to those without the condition.

One recent study suggested that people with autism tend to have far more activity in the part of the brain called the amygdala when looking at other people's faces. The over-stimulation of this part of the brain that deals with new information may explain why people with autism often have difficulty maintaining eye-contact.

Specific nerve cells in the brain, called neurones, also act differently in people with autism. Mirror neurones help us mimic useful behaviour so we can learn from others.

Brain imaging studies suggest that the mirror neurones in people with autism respond in a different way to those without the disorder.

This could partly explain what many behavioural studies have already shown - that children with autism can find it difficult to copy or learn simple behaviours from others. Scientists have suggested with social interaction could have a knock-on effect on language learning.

What is Asperger syndrome?

Asperger syndrome is a milder form of autism, with symptoms that affect social interaction and behaviour.

Children with Asperger syndrome are often of average or above intelligence, and may be particularly good at learning facts and figures. However, they may also lack imagination and find creative play or thinking in the abstract very difficult.

What causes autism?

Autistic spectrum disorders

  • Estimates suggest that one in 100 people in the UK have autism
  • Four times as many boys as girls are diagnosed with autism
  • The number of diagnosed cases of autism has increased over the past 20 years, thought to be due to better diagnosis
  • There is no cure but there are a range of interventions available

Sources: NHS Choices/National Autistic Society

The exact causes of autism are not yet understood but researchers believe genetic, environmental and neurological factors play a part.

In fact autism is probably not one single condition but encompasses a group of disorders that have their roots in a variety of different causes, but which result in similar problems.

Researchers are examining a number of specific genes that could contribute to the disorder. It's likely that autism occurs when a small number of genes interact in a specific way, possibly linked to some external event or factor.

The genetic link means a predisposition to autism may be inherited and can run in families. Brothers or sisters of a child with the condition are 5-6% more likely to develop it themselves.

A variety of other environmental factors that affect development before, during or soon after birth, may also play a part.

Researchers believe that if a child is exposed to certain situations it may trigger the disorder. These potential triggers include if the mother has an infection or smoked during pregnancy and if the father is over 40 years old.

Despite reports suggesting a possible link between MMR vaccination and autistic spectrum disorders, scientific evidence has confirmed the vaccination does not increase the risk.

Future of research?

Scientists are spending much of their time studying how autism may affect brain function. Research has found that people with autism may have larger brains than average, which grow unusually fast in early childhood.

Connections between different areas of the brain may also differ. However, further research is needed to fully understand the implications of these findings.

Scientists are also measuring magnetic and electrical activity in the brain using sensors placed on the outside of the skull to try and better understand the disorder.

For symptoms and more information, visit NHS Choices

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