Researchers have revealed that environment has the same intensity to cause autism as genes do. After having one child with autism, parents often worry the risk of having the next one with the disease because same genes have the potential of repeating the unwanted.

However, the largest analysis to date to look at how the brain disorder runs in families has claimed that heritability is only half the story, as environmental factors also play a significant role in causing autism.

The environmental factors, like birth complications, socioeconomic status, or parental health and lifestyle, have not been previously considered important as a serious cause of autism. But, the new research has debunked the belief, saying environmental risk factors also have a significant role to play in causing autism, in addition to range of genetic factors.

As per figures, one in 50 school-age children in the US is detected with autism. However, some of these cases are milder because of better recognition of autism symptoms by caregivers and doctors.

Previously, most studies have majorly linked autism with genetic factors, with a risk as high as 80 to 90%. But this new study has found that genetic disorders only contribute 50% to cause the mental disorder and remaining 50% role is played by environmental factors. The researchers reached at the conclusion after using Swedish national health registers and analysis of anonymous data from all two million children born in Sweden in between 1982 and 2006. Of them, 14,516 of has been diagnosed with autism.

"Heritability is a population measure, so whilst it does not tell us much about risk at an individual level, it does tell us where to look for causes", said Avi Reichenberg, of the Mount Sinai Seaver Center for Autism Research, who worked on the study while he was at King's College London.