Fever can temporarily improve the behaviour of children with autism spectrum disorder, researchers have found in a surprising study that may shed further light on the condition.

The researchers think that a high fever has an effect on behaviour because it restores nerve cell communications in regions of the autistic brain. That then restores the child's ability to interact and socialize.

The small study, published in the journal Pediatrics, is based on 30 children with autism aged 2 to 18. The researchers asked the parents of the children to record their children's behaviour during a fever of at least 100.4 degrees Fahrenheit, immediately after the fever had abated, and when the child had been fever-free for seven days.

The parents recorded fewer aberrant behaviors, such as stereotypy (repeated, ritualistic movements), irritability, hyperactivity, and inappropriate speech during and immediately after a fever.

The behavior improvement occurred regardless of the severity of the fever and the illness. As expected, the improvements in behaviour ended when the fever broke.

The researchers say their findings suggest that the behaviour changes were not solely the result of the sickness itself. But they say more research is needed to confirm the link, and to determine the causes of the behaviour change.

Dr. Andrew Zimmerman, a pediatric neurologist at Baltimore's Kennedy Krieger Institute, who was one of the study authors, says the findings give researchers important clues about autism.

"The results of this study are important because they show us that the autistic brain is plastic, or capable of altering current connections and forming new ones in response to different experiences or conditions," he said.

He said the effect of fever on behaviour was likely to be observed only in children, whose brains are more "plastic" than those of adults.

Zimmerman hopes the research could point the way to better treatments that would "reconnect" the autistic brain.

People with autism spectrum disorders suffer in varying degrees from limited social interactions, lack of verbal and non-verbal communication and other abilities. It is not known what causes the condition.