Autism Is Mostly in the Genes, Study

So what exactly is the root cause of autism?

Simple. It is almost fully genetic. New research shows that between 74 and 98 per cent of autistic patients are because of biological make-up.

In a research by the Medical Research Council, a study of 516 twins showed that Autism Spectrum Disorder (ASD) is higher in identical twins who share their DNA, according to independent.

Hence, autism is genetically determined. Inheritance is responsible for autistic traits and behavior among the general public.

While one in every 100 people in the UK has autism, according to BBC.

Lead author of the research, Beata Tick, said: "Our main finding was that the heritability of ASD was high. These results further demonstrate the importance of genetic effects on ASD, despite the dramatic increase in prevalence of the disorder over the last 20 years.

"They also confirm that genetic factors lead to a variety of autistic skills and behaviours across the general population."

However, the scientists, who examined information from the 'population-based Twins Early Development Study (Teds)' which involved pairs of twins in the same household by the same parents, said that environment too could play a role. Co-author Professor Patrick Bolton said: "The comparison of identical and non-identical twins is a well-established way of clarifying the extent of genetic and environmental influences in autism.

"The novel aspect of this study was the inclusion of twins regardless of whether they had a clinical diagnosis. This enabled us to get a more accurate picture of how influential a child's environmental experiences and their genetic make-up is on ASD, as well as on subtler expressions of autistic skills and behaviours. Our findings add weight to the view that ASD represents the extreme manifestation of autistic skills and behaviours seen in the general population."

A scientist Dr Francesca Happe agreed that the recent spike in the autistic rates might be due to accurate diagnoses. The disorder is part of a range of conditions that are diverse, and were earlier considered a learning disability, not autism, according to BBC.

"Our findings suggest environmental factors are smaller, which is important because some parents are concerned whether things like high pollution might be causing autism," she said. "Some people think there might be a big environmental component because autism has become more common in recent years but that's happened too fast for genetics to be a probable cause. The main consensus now is that the rise in diagnosis has more to do with increased awareness of the condition."

However, other factors include the ambience, including "prebnatal exposure to toxins", such as the chemicals thalidomide and valproic acid. Additional risks could be parental age during the conception of the child, the mother's nutrition and infection.