BRISTOL, UK:  British researchers are to to carry out one of the most detailed studies into the links between autism and the environment.

A Bristol University team will examine whether vaccinations play a part in the development of autism. They will also explore the possible impact of problems with birth, diet, infections and exposure to toxins, and will test the theory that other conditions, such as coeliac disease, may increase the risk.

More than 500,000 people in the United Kingdom are estimated to be affected by autism spectrum disorders.

Some scientists have suggested the triple MMR (measles, mumps, rubella) jab may be linked to autism. However, no research has ever proved a link, and the overwhelming majority of experts believe the vaccine is safe.

The new research will be based on data generated from 14,000 children already taking part in the Children of the '90s study - a long-term project to examine the role of environment and genes on children's health.

The lead researcher, Professor Jean Golding, said: "Because of the number of children we'll be looking at, and the quality and type of data available, our study should help find the answers to a number of currently unanswered questions about the environmental risks for developing autism spectrum disorders.

"One theory suggests that the causes of autistic behaviours arise very early in pregnancy - even in the first few weeks.

"While it is true that this disorder does sometimes run in families, it isn't purely genetic. One possibility is that something happens in the womb, which interacts with a gene - and the result is a child with an autistic spectrum disorder.

"For instance, is there evidence that the mothers of children with particular autistic traits were exposed to infections more often in pregnancy than mothers of unaffected children?

"A number of possible causes have been suggested - and we shall be testing various hypotheses concerning the cause and origin of each trait, whether it is genetic or environmental."

The £400,000 study of 14,000 children - the money comes from the British Department of Health and the Scottish Executive - is likely to be too small to settle the MMR vaccination debate convincingly.

The Children of the '90s project began in 1991. It is following 14,000 mothers and their children in detail to trace links between their way of life and disease. The children are now aged 11 to 13. About 140 of them are thought to have been diagnosed with an autistic spectrum disorder. That number is too small to draw any conclusions about MMR and diagnosed autism.

So the team will look at the four character traits that are used to diagnose autism: delayed language development, poor communication, repetitive behaviour and limited empathy.

The Bristol University project is one of four studies into autism funded by the Medical Research Council. These include using imaging techniques to examine differences in the brain anatomy of adults with autism.

(Sources: The Daily Telegraph; BBC News Online,  July 8, 2004)