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Environmental Contributions to Autism: Looking Beyond Twins

 
 
Miller
 
Reply Tue 3 Jun, 2014 01:52 pm
The Genetic and Environmental Contributions to Autism, :Looking Beyond Twins
Diana E. Schendel, PhD1,2,3; Therese K. Grønborg, MSc4; Erik T. Parner, MSc, PhD4

Abstract:
Autism spectrum disorders (ASDs) are serious neurodevelopmental disorders characterized by difficulties in social interaction and communication accompanied by stereotypical, repetitive behavior and restred interests. Once considered rare, ASD is now reported to affect approximately 1% to 2% of children. The increase in ASD prevalence in recent decades combined with little understanding of ASD etiology have fostered increases in public and private research funding with a substantial investment in genetic research. The historical focus on genetic factors partly arose from evidence from the first twin studies in which concordance for an ASD diagnosis was reportedly as high as 90% in monozygotic twins and substantially higher than in dizygotic twins. A more recent and larger twin study, however, observed a smaller genetic effect and a larger environmental effect on ASD liability than previous work, suggesting that early estimates of the genetic liability for ASD may have been inflated by ascertainment bias. Along with twin concordance, another important measure of genetic contribution to disease is familial recurrence. Estimates of sibling recurrence of ASD in families with a previously diagnosed child have ranged from 5.8% to 18.7%, which are markedly higher than the occurrence of ASD in the general population and thereby support the importance of familial contributions to the risk for ASD.
JAMA. 2014;311(17):1738-1739. doi:10.1001/jama.2014.3554.


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bobsal u1553115
 
  1  
Reply Tue 3 Jun, 2014 02:37 pm
@Miller,
Really interesting article. I wonder if a large portion of our population isn't some form or degree autistic.
Miller
 
  1  
Reply Tue 3 Jun, 2014 02:46 pm
@bobsal u1553115,
bobsal u1553115 wrote:

Really interesting article. I wonder if a large portion of our population isn't some form or degree autistic.


So do I.
0 Replies
 
boomerang
 
  2  
Reply Tue 3 Jun, 2014 04:07 pm
Huh.

I just read this today --

Quote:
Research on children in Denmark has found that boys with autism were more likely to have been exposed to higher levels of hormones in their mother's wombs than those who developed normally.

Boys diagnosed with autism and related disorders had, on average, raised levels of testosterone, cortisol and other hormones in the womb, according to analyses of amniotic fluid that was stored after their mothers had medical tests during pregnancy.

The findings add to a growing body of evidence that the biological foundations of autism are laid down well before birth and involve factors that go beyond the child's genetic make-up.


Full story: http://www.theguardian.com/society/2014/jun/03/boys-with-autism-likely-exposed-to-more-hormones-in-the-womb
Miller
 
  1  
Reply Wed 4 Jun, 2014 07:34 am
@boomerang,
The Guardian is not a peer-reviewed journal.
boomerang
 
  2  
Reply Wed 4 Jun, 2014 08:08 am
@Miller,
They were just reporting the findings.

The research was done at the Autism Research Centre at Cambridge University, in association with scientists in Denmark.
0 Replies
 
bobsal u1553115
 
  2  
Reply Wed 4 Jun, 2014 09:51 am
@Miller,
Found this:
Autism Tied to High Levels of Prenatal Steroid Hormones

Backs environmental causation.

By Makiko Kitamura Jun 3, 2014 3:00 AM CT

Boys who develop autism are exposed to higher levels of steroid hormones in the womb than those who don’t develop the condition, according to a study that further dispels the role of vaccines.

Prenatal levels of substances such as testosterone, progesterone and cortisol were greater on average in boys who were later diagnosed with autism, scientists at the University of Cambridge in England and the Statens Serum Institute in Copenhagen said in a report released today.

The finding, published in the journal Molecular Psychiatry, provides a possible explanation for how autism develops during pregnancy, countering fears that external factors such as vaccines play a role. Autism spectrum disorders, a group of brain development disorders, affect about one child in 160, according to the World Health Organization.

“We previously knew that elevated prenatal testosterone is associated with slower social and language development, better attention to detail and more autistic traits,” Simon Baron-Cohen, professor of developmental psychopathology at Cambridge, said in a statement. “Now, for the first time, we have also shown that these steroid hormones are elevated in children clinically diagnosed with autism.”
Amniotic Fluid

The study drew on 19,500 amniotic-fluid samples stored in a Danish biobank from individuals born between 1993 and 1999. The researchers identified samples from mothers who gave birth to 128 boys later diagnosed with an autism-spectrum condition. Because some of the hormones are produced in much higher quantities in males than in females, the finding may help explain why autism affects more boys, the researchers said.

“We now want to test if the same finding is found in females with autism,” Baron-Cohen said.

Mothers shouldn’t rush to use steroid-hormone blockers, as this may have unwanted side effects, according to Baron-Cohen. The study also shouldn’t be interpreted as indicating a need to develop a prenatal screening test as the results were found at the average group level and may not predict diagnosis for an individual, he said.

The study results suggest there’s variation in individual sensitivity to hormones or that the investigated time window is too early to detect a true elevation of hormone levels, said Richard Sharpe, a professor specializing in male reproductive health at the University of Edinburgh.
Not Vaccines

“Researching this in humans is incredibly difficult because of the obvious limitations in accessing what is happening in the fetus inside the womb, so investigations such as the present study have to be viewed as pioneering,” Sharpe said in an e-mailed statement.

The study adds to earlier research suggesting that autism is linked to prenatal developments.

A paper published in March in the New England Journal of Medicine found that those diagnosed with autism missed key genetic markers for brain cells that are supposed to develop prior to birth.

A Norwegian study published last year found that taking folic acid supplements in early pregnancy was linked to a lower risk of autistic disorder. Folic acid is needed to fuse the spinal cord in early fetal development.

Vaccination has been feared as a potential cause of autism after a study by Andrew Wakefield, published in the Lancet medical journal in 1998, linked the measles-mumps-rubella vaccine to an increased risk of developing the condition. The Lancet retracted the study in 2010, citing “false” claims, and the British Medical Journal called it a fraud in a report the following year.

A study published about 14 months ago in the Journal of Pediatrics by researchers at the Centers for Disease Control and Prevention in Atlanta confirmed earlier research findings that autism risk isn’t increased by the use of childhood vaccines.

To contact the reporter on this story: Makiko Kitamura in London at [email protected]

To contact the editors responsible for this story: Phil Serafino at [email protected] Tom Lavell, Marthe Fourcade
0 Replies
 
InfraBlue
 
  1  
Reply Wed 4 Jun, 2014 12:14 pm
Here's the link to the peer reviewed journal referenced in boomerang's article.
Miller
 
  1  
Reply Wed 4 Jun, 2014 12:26 pm
@InfraBlue,
Did baby girls, who developed autism after birth, also show this increase in testosterone level relative to girls who never developed autism?
Foofie
 
  1  
Reply Wed 4 Jun, 2014 12:31 pm
And now for something completely different:
http://www.rdos.net/eng/asperger.htm
0 Replies
 
Miller
 
  1  
Reply Wed 4 Jun, 2014 12:46 pm
@Miller,
A critical issue is the relationship between the hormone level in the amniotic fluid ( which is what is being measured) and the level of hormone transported into the fetus. And...then the comparison of these results with severity of autisic behavior.

I don't think that this type of human experimentation has ever been performed.

If there is an animal model for autism, perhaps this type of experiment can be performed.

0 Replies
 
 

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