More research finds a family-based risk of autism among siblings, which raises the question of what parents can do to lower the risk among potentially at-risk youngsters.
Researchers from Aarhus University in Denmark report in the journal JAMA Pediatrics that children with an older brother or sister diagnosed with an autism spectrum disorder (ASD) are more likely to be on the spectrum themselves.
According to their study of about 1.5 million children born in Denmark between 1980 and 2004, those who had an older sibling diagnosed with autism had close to a seven-fold increased risk of developing autism as well. Siblings who shared the same mother and father had a 7.5 greater risk of having autism, whereas maternal half siblings had a 2.4 greater risk. Paternal half siblings didn’t have a statistically significant increase in risk.
The results clearly support the strong role that genetics plays in autism. And the higher rates among half siblings who share a mother also highlight the role that pregnancy factors could play. Last week, researchers from Duke University and the University of Michigan reported that augmented or induced labor, for example, could contribute to a higher risk of autism among children.
For parents, the findings raise difficult questions about how proactive they should be in screening for the disease among their younger children if older siblings are affected. Alycia Halladay, senior director, environmental and clinical sciences for Autism Speaks, says parents who have already had a child diagnosed on the spectrum should alert their doctor to the family history. During check-ups, when a doctor asks about inherited disorders like cystic fibrosis, they now typically include autism on the check-list.
Mothers of autistic children can also take steps during pregnancy to lower the risk of autism in their next offspring, such as taking prenatal folic acid and avoiding overexposure to toxins. That attention could even extend to the infants’ first few years, since studies suggest that some intensive behavior therapies can help to mitigate the symptoms of autism. “We know that early intervention can make a real lifetime of difference. So be very vigilant during that child’s life, all the way from birth to the well baby check-ups, six months, 12 months, and 18 months,” says Halladay. “Make sure you are watching for the signs and symptoms of autism. Consult your pediatrician, and if you do notice the signs and symptoms of autism you can receive help free of charge from a state-based early intervention agency.”
Researchers are also developing tests that can detect the genetic risk factors associated with the disorder, and more of these biomarkers may become available as additional gene-based contributors emerge. Scientists from University of Utah and the Children’s Hospital of Philadelphia, for example, recently identified 24 new gene variants associated with autism spectrum disorders in January.
Understanding what these various gene differences mean, however, is still a work in progress. “The genetic tests that are out there really look for specific genes that we know are associated [with ASDs], but if you don’t have these specific genes, there could be a combination of other genes your child has that could increase that risk,” she says. “Just because your child doesn’t have that biomarker, doesn’t mean that child is not at risk. There is a lot we don’t know about genetics, that we still need to understand to get to a point where we are comfortable saying here is definite risk marker, or here is a test that a parent can take.”
For now, simply being aware that siblings of autistic children may be at higher risk of the disorder could help parents to pay more attention to the signs and symptoms of autism so they can alert their doctors as early as possible in the child’s development.