The risk of a family with one child on the autism spectrum of having another with the disorder is only around 5 percent – much lower than the estimated 20% that has been claimed in foreign studies, according to a Hebrew University of Jerusalem study.The study, carried out in cooperation with the National Insurance Institute’s research and planning administration, is based those who receive allotments from the NII to help cover the costs of children with autism. It gives parents accurate assessments on the risks based on characteristics of the families.Autistic spectrum disorders represent a variety of the neurodevelopmental diseases that are diagnosed in around one in 20 children, more commonly in boys than in girls.The NII said that parents with one autistic child struggle over whether to have more children – as shown on the Channel 2 TV series Yellow Peppers. A US study in 2011 claimed that there was a one-in-five risk of having a second symptomatic child because of genetic causes.But the NII researchers say now that the US study was based on a “small and biased sample.”A Danish and Swedish study from three years ago said that there was a one-in-14 risk of having another autistic child.Prof. Michael Beenstock of the Hebrew University’s economics department and Dr. Ra’anan Raz and Dr. Haggai Levine of the Hebrew University-Hadassah School of Health and Community Medicine investigated the risk factors for repeated autism in families.Using the extensive NII database to research how many families actually applied for disability support for autistic children, they found that between 1986 and 2012, there were 9,117 Israeli families with one autistic child, 362 with two and just three families with three.For 1,033 families, there was one autistic child who had no subsequent siblings. For 3,185 families with one autistic child, they had only normal children before the disabled child was born and they had no more children after the disabled child’s birth. Thus a total of 4,898 families had 8,188 children whose younger siblings had autism. The risk of a subsequent autistic child was only 4.5%, according to the database.As most diagnoses are made up to the age of four, waiting for the child to be older led to a repeat rate of 5.25% among families where the affected child was diagnosed at an older age.The risk of a repeat autism child is 10 times that in families that already have a child with autism compared with families that have none. This points to the genetic basis for autism, the researchers said, but there may be environmental factors in which offspring were exposed to toxins or pathogens that contributed to the development of autism.More studies of this type are needed based on population data, so that decisions can be made by the family and the population in general, the authors concluded.