Various factors that lead to autism like the environment, genetics and the immune system have been discovered by a new study.

Two biologically different kinds of development in the brain were found by a study that was conducted on about 350 children in the US among kids who have autism and concluded that there are likely to be more.

According to Dr David Amaral, the head of the Autism Phenome Project at the University of California, among some boys the size of the brain will be too large too soon and these are the boys who are autistic.

He said that in girls this is not seen and when it comes to boys, only in a subset of children suffering from autism show this.

Similar symptoms are there in different types of autism, according to Dr Amaral.

He said, "That's one of the mysteries at this point. We know that there are different biologies but that the behavioural symptoms of children with autism all look basically the same."

It is now being found out if there is one final common pathway for all of these biological causes.