Autism spectrum disorder (ASD) and autism are both general terms for a group of complex disorders of brain development. These disorders are characterized, in varying degrees, by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviors.
ASD can be associated with intellectual disability, difficulties in motor coordination and attention and physical health issues such as sleep and gastrointestinal disturbances. Some persons with ASD excel in visual skills, music, math and art.
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.