Half Genes, Half Environment

Examining more than 20 years of Swedish birth records, researchers determine that autism risk is influenced equally by genetic and environmental factors.

By Jef Akst | May 5, 2014

An 18-month-old boy with autism likes to stack cans.WIKIMEDIA, COUNTINCRAutism spectrum disorder (ASD), a complex developmental disease that affects nearly 1 percent of US children, has long been recognized to have both genetic and environmental influences. Now, through a review of more than 2 million births in Sweden between 1982 and 2006, researchers led by Sven Sandin of King’s College London and the Karolinska Institutet in Stockholm determined that both the heritability of ASD the environmental component each comprise approximately 50 percent of the risk. Moreover, children born into a family in which a sibling or cousin has previously been diagnosed with ASD are at a greatly increased risk: those with an autism-afflicted sibling have a 10-fold greater risk of being affected themselves, while those with an autism-afflicted cousin are twice as likely to be diagnosed with ASD. The team’s results were published this weekend (May 3) in JAMA.

“[T]he work by Sandin et al. supports appreciation of the importance of genetic factors in ASD and adds substantial impetus to the growing attention to environmental influences in ASD etiology,” Diana Schendel of Aarhus University in Denmark and colleagues wrote in an accompanying editorial.

The authors noted that better understanding the risks of ASD could help affected families decide whether they would like to have additional children. “The risk of autism increases according to how close you are genetically to other relatives with autism. We can now provide accurate information about autism risk which can comfort and guide parents and clinicians in their decisions,” Sandin told The Telegraph. “Some will want to avoid having another autistic child, but for others it won't be a problem.”

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Avatar of: wctopp


Posts: 110

May 5, 2014

I'd guess that the environmental contribution to epigenetic inheritance, if present, would be present equally for all children of a single female so it probably wouldn't much skew this result.  The bias would be more towards environment, if anything.

Avatar of: concerned


Posts: 1

May 5, 2014

It is time to give some serious consideration to one of the most common environmental exposures for both pregnant women and children. We now have two large population studies that show an association between the prenatal use of PARACETAMOL (acetaminophen or Tylenol) and adverse neurodevelopment.

The first study, by Brandlistuen et al.2013, found that 3 year old children exposed to long term paracetamol use during pregnancy had substantially adverse developmental outcomes, including a 70% increased risk of behavioral and motor problems, as well as, double the risk of communication problems. The second study, by Liew et al. 2014, found that prenatal exposure to paracetamol increased the risk of ADHD, behavioral problems and hyperkinetic disorders in 7 year olds.

Paracetamol exposure can potentially account for the 4-5 times higher prevalence of autism among males. Males are differentially exposed and differentially susceptible to acetaminophen toxicity. The WHO and AAP recommend 5-7 doses of paracetamol with the circumcision procedure. The paracetamol sales timeline corresponds with the autism prevalence timeline, and multiple animal models show paracetamol to have neurotoxic effects leading to behavioral abnormalities.

Avatar of: PastToTheFuture


Posts: 117

Replied to a comment from concerned made on May 5, 2014

May 5, 2014

Fascinating. Thanks

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