new study suggests that environment might be a bigger player in <"http://www.yourlawyer.com/practice_areas/diseases">autism diagnoses than previously believed. According to WebMD, the information was derived from one of the largest twins studies conducted, to date.
The study, which appears in the Archives of General Psychiatry, found a striking incidence of autism in fraternal twins even though their shared genes are less prevalent than those in identical twins. The finding, said WebMD means that it is likely that some element in the twinsâ€™ â€œlife circumstancesâ€ might have as much of an impact as genetics on a diagnosis of autism.
â€œThere are lots of neuroscience papers that begin â€˜Autism is one of the most heritable conditions in psychiatric genetics and shows over 90% heritability…â€™ and I donâ€™t think people should start their papers that way anymore,â€ says Harold Hill Goldsmith, PhD, a professor of psychology at the University of Wisconsin at Madison, quoted WebMD. Goldsmith, who is on the board of Autism Speaks, is studying autism in twins, but was not part of this research.
A few smaller studies conducted in the past 30 years revealed that it is more common for identical, not fraternal twins, to be diagnosed with autism, leading to the prevailing theory that autism is a DNA-driven disorder and that a smaller percentage of the population develops autism as a result of environmental issues, said WebMD. That long-standing belief is now being called into question.
According to Goldsmith, the new California research is one of four other new investigations into autism in twins, said WebMD. Two other studies are being conducted in the United States and two studies are being conducted in Europe. Goldsmith said that while genes are a factor, they may not account for everything.
The research team, meanwhile, said they did not expect the results they received. â€œIt was a surprise, definitely,â€ said study researcher Joachim Hallmayer, MD, an associate professor of psychiatry at Californiaâ€™s Stanford University, quoted WebMD. â€œIt looks like some shared environmental factors play a role in autism, and the study really points toward factors that are early in life that affect the development of the childâ€¦. We have to look also at environmental factors, and from my point of view, the interaction between the genetic factors and the environmental factors,â€ he added, quoted WebMD.
The study reviewed a California registry of children receiving services for developmental disabilities. The team identified 192 sets of twins in which at least one child was diagnosed with autism or an autism spectrum disorder (ASD), such as Aspergerâ€™s syndrome, said WebMD. ASDs include autism, Aspergerâ€™s syndrome, and pervasive developmental disorder not otherwise specified. All involve issues with social interaction, both verbal and nonverbal communication, and repetitive behaviors. The study involved 54 sets of identical and 138 sets of fraternal twins. Standard psychological assessments were used to confirm diagnoses.
The researchers found that environment could potentially account for 58 percent of the risk for ASDs; genetics accounted for 38 percent, reported WebMD. Goldstein said that, â€œEveryone in this field understands that genetics doesnâ€™t explain this fully and thereâ€™s going to be an environmental component to triggering vulnerable people or maybe even causing it in some people without a vulnerability gene,â€ quoted WebMD.
And, while itâ€™s true that reports of ASDs are on the rise, in part because of better diagnostic tools, many maintain that the increase is due to environmental exposures such as PCBs; mercury; vaccinations; pesticides; pollution; and high-fructose corn syrup (HFCS), which was found in two studies to contain mercury.
Yesterday, we wrote that a new study reported that babies born to women taking selective serotonin reuptake inhibitors (SSRIs)â€”antidepressants such as Prozac, Luvox, Paxil, and Zoloftâ€”when pregnant may experience an increased risk for developing ASD, according to WebMD.