Autism in our lives
The Star/Asia News Network
By Dr Milton Lum
Autism is a developmental disability that results in problems with social interaction and communication. Its features vary with individuals.
One person may have mild symptoms, whilst another may have serious ones. That is why healthcare providers consider autism a "spectrum" disorder, which includes an autistic disorder, Asperger syndrome, and pervasive developmental disorder (atypical autism).
Children who have an autistic disorder have major problems with language, social interaction and behaviour. Many also have learning problems and intelligence that is below average.
Children with Asperger syndrome have milder symptoms affecting social interaction and behaviour. Their language development is usually alright but they can have problems in certain aspects of language, for example, understanding humour. Their intelligence is usually above average. Some are skilful in memory, logic and creativity, eg in music, and pure sciences.
Children who have some, but not all of the features of autistic disorder and/or Asperger syndrome, are said to have a pervasive developmental disorder. Most have milder symptoms than autistic disorder but do not possess the good language and above average intelligence of Asperger syndrome.
Looking at the causes
Autistic spectrum disorder (ASD) can be due to primary or secondary factors. There is no medical condition in the former, which comprises 90 per cent of ASD. A medical condition is thought to be wholly or partially responsible for the latter, which comprises 10 per cent of ASD.
The conditions in secondary ASD are fragile X syndrome, tuberous sclerosis, and Rett syndrome.
Fragile X syndrome affects about one in every 3,600 boys and 6,000 girls, who have characteristic long faces, large ears and flexible joints. Tuberous sclerosis affects about one in 6,000 children, who have multiple, non-cancerous tumours all over the body. Rett syndrome affects about one in 20,000 girls who have ASD, and they have problems with physical movement and development.
Primary ASD is associated with genetic, environmental, neurological and psychological factors.
Although there is no specific gene identified, ASD is known to occur in families. If a child has ASD, there is about a 5 per cent chance that another child born to the same parents will have ASD. If an identical twin has ASD, the chance of the other twin developing the condition is 60 per cent.
The environmental factors associated with ASD are viral infection and maternal smoking during pregnancy, and the father's age. Pregnant women exposed to rubella have a 7 per cent chance of having an ASD child. The chance of pregnant women who smoke daily having a child with ASD is 40 per cent.
First time fathers above 40 years of age are six times more likely to father a child with ASD.
Studies on neurological factors have focused on the brain's amygdala, which acts like a switchbox between the cerebral cortex and the limbic system. The former processes sensory information and is responsible for all the brain's higher functions like thought, language, and problem-solving, while the latter controls a person's emotions.
The amygdala chooses the emotion to match the situation a person is in. Brain imaging studies suggest that connections between the cerebral cortex, amygdala and limbic system are altered in ASD.
Other studies have focused on mirror neurones which are thought to enable copying of the actions of others, eg an infant returns a mother's smile. As the child grows up, the mirror neurones may be involved in the brain's higher functions like language, learning, and recognition and understanding of others' emotions.
Brain imaging studies have found that the response of mirror neurones is altered in ASD. This mirror neurone dysfunction may be responsible for the problems with language, social interaction and some aspects of learning in ASD.
The focus of research on psychological factors is the concept of "theory of mind" (TOM). TOM refers to a person's ability to understand the mental states of others, ie the ability to see the world through another person's eyes. It is believed that most children understand TOM fully by about four years of age. Children with ASD have a limited or non-existent understanding of TOM, which may explain their problems with social interaction.
Although there are reports of links between vaccines and autism, none have held up to scientific scrutiny. There is no conclusive evidence that any part of a vaccine or combination of vaccines causes autism. There is also no evidence that any material used to make or preserve vaccines play a role in the causation of autism.