Who are the children that may go on to develop autism? Researchers from the Center for Autism Research at San Diego believe that the autistic child is born with an unusually small head, and brain, and then experiences extraordinary head and brain growth.
Their theory is supported by their own research, based on a small group of 48 autistic children, and by earlier research. One study noted that 90 per cent of autistic children, aged between 2 and 3, had larger brain volumes than average and an abnormally large head circumference. Another study reported that brain size in 4-year-old children with autism exceeded the healthy average.
The new study by the Center confirmed these findings, but also discovered that the autistic child is more likely to be born with small head size. Sudden, and excessive, growth of the brain and head then occurs one to two months after birth, and again between six and 14 months.
These growth spurts happen long before autistic tendencies – such as delayed speech, poor attention and unusual social behaviour – start to appear, which usually occurs during the second and third years of life.
But sudden head and brain growth is not the cause – it’s just another indicator. Admittedly, only around 6 per cent of non-autistic children experience the same sort of sudden brain and head growth, but it’s still a significant minority. Similarly, other studies suggest that the growth pattern happens only to 59 per cent of autistic children, so a sizeable minority have normal brain growth patterns.
So, while health authorities would love to seize on this new research to dampen down concerns about a link between autism and the MMR vaccine, this trial doesn’t give them the let-out they’re looking for.
(Source: Journal of the American Medical Association, 2003;290: 337-44).