Children who were diagnosed with autism had far less mercury in their hair than other babies, researchers found.
One explanation might be that autistic children have a problem absorbing metals. They could, therefore, also be deficient in metals essential for brain development, such as zinc, iron and copper. Alternatively, the discovery could indicate that the children are not excreting mercury properly, allowing it to build up in the brain.
The second theory might suggest a link with certain vaccines that contain a mercury-based preservative – although there is no evidence for this yet.
A report in New Scientist magazine stressed this did not apply to the MMR vaccine, which contains no mercury.
Dr Amy Holmes, from Louisiana, USA, who led the research, obtained first cuttings of baby hair from parents and sent them off for analysis.
Hair from 94 autistic children was compared with that from 45 non-autistic children.
The average level of mercury in hair from infants later diagnosed as autistic was 0.47 parts per million, compared with 3.63 ppm for the others.
