Autism Cases on the Rise; Reason for Increase a Mystery
Scientists are scouring genetic and evironmental data to find a cause for the rise in autism.
Getting to the Causes of Autism continued...
"This is harder than cancer because in cancer you can biopsy it; you can see it on an X-ray," Goldstein says. "We don't have a blood test [for autism]. There is no biomarker, no image, no pathology."
"There won't be one single explanation,'' says Marvin Natowicz, MD, PhD, a medical geneticist and vice chairman of the Genomic Medicine Institute at the Cleveland Clinic.
"There's been a lot of progress in the last few years in terms of understanding the causes of autism," Natowicz says. "We know a lot more than we did." Still, he says, research has a long way to go. "One number you see often is that about 10% of those with autism have a definitive diagnosis, a causative condition." The other 90% of cases are still a puzzle to the experts.
Often, a child with autism will have a co-existing problem, such as a seizure disorder, depression, anxiety, or gastrointestinal or other health problems. At least 60 different disorders -- genetic, metabolic, and neurologic -- have been associated with autism, according to a report published in The New EnglandJournal of Medicine.
On one point most agree: A combination of genetics and environmental factors may play a role. Scientists are looking at both areas.
Zeroing In on the Genetics of Autism
Some evidence that genetics plays a role in autism and ASD is provided by research on twins. According to the CDC, if one identical twin has autism, there's a 75% chance the other twin will be affected, too. If a fraternal twin is affected, the other twin has a 3% chance of having autism.
Parents who give birth to a child with ASD have up to an 8% chance of having another child who is also affected, the CDC estimates.
Many U.S. couples have delayed childbearing, and the older ages of both the mother and the father have been linked with a higher risk of having children with ASD, according to a report in the journal Pediatrics. With age could come increased risk for genetic mutations or other genetic problems.