Genetics Or Environment?
The debate rages on; is autism an inherited (genetic) condition or is it caused primarly by environmental factors?
A recent study in California looked at sets of twins with autism. The researchers looked at both identical twins and fraternal twins (non-identical). In identical twins the DNA is identical between the twins, whereas in fraternal twins only half the DNA is shared.
If autism was primary a genetic condition then one would expect identical twins, who have identical DNA, to both be autistic whilst fraternal twins would have a much lower ratio of autistic to non-autistic twin.
Conversely if autism was primarily an environmental condition then one would expect the fraternal twins and identical twins to have similar ratio of autistic to non-autistic twins.
What the researchers found was that there appeared to be a significant genetic contribution to whether both twins would be autistic; however there was a greater environmental component in determining if both twins were autistic. based on their findings the authors calculate that
shared environment accounts for 55% of the risk of autism and 37% for genetic heritability.
There’s an abstract of the report in the Archives of General Psychiatry or, if you’d like to read a fuller discussion, please see Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism on Left Brain Right Brain.
Vaccines and Autism? Report Finds No Link
Image thanks to The BBC
A new report has been published by the US Institute Of Medicine that looked at vaccines and any adverse effects they might cause.
Whilst string correlation was found between some vaccines and side effects no evidence was found of a link between the MMR vaccine and autism.
I think this is good news; but I wonder how deeply the concept of “MMR and autism” have become ingrained in our collective sub-conscious so that people will still refuse the MMR for fear that it can lead to autism.
Has this affected your decision to vaccinate your children? Has this new information changed your mind? Leace a comment and let us know.
Autism Risks For Siblings
A new study in the US has reported some interesting findings for parents who already have a child on the autistic spectrum. Previous studies indicated there was between 3% and 10% risk of having a second child being diagnosed with ASD if there was an older sibling with the condition. However these past studies were limited by small sample sizes and other factors.
The results published this week by the American Academy of Pediatrics took a much larger sample (664 children) from an average of 8 months on to 36 months at which time they were assessed by an “expert clinician” as either having autism or not having autism.
The researchers found there was an 18.7% likelihood that a child with an older sibling with ASD would also develop ASD. That is significantly higher than previously thought. Where there was more than one older sibling with ASD the risk further increased to 32%! There was a significantly greater risk in boys compared with girls. The gender, age or severity of the ASD in the older sibling did not affect the likelihood of the younger sibling being diagnosed on the spectrum.
This is probably not what you want to read if you’ve a child on the spectrum and you’re contemplating a larger family. I think the increase is partly due to the increased sample size and improved sampling methods; but also to the fact that we now have a much wider definition of autism compared with the earlier studies that were carried out in the 1980s and 90s. The researchers also point out that:
Many families actually believe that the risk to later-born siblings is higher [my emphasis] than either the current investigation or previous studies suggest it to be.
So it’s important that up to date information is made available to parents. You can read the report in full at Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study
Research Opportunity
I’ve received this request for assistance via our Facebook page. If you think you can help out please drop Tracey a line (mind you I think she’s got a hope finding anyone down this way with a diagnosis as early as 3 years old).
I am looking for parents of children with ASD (e.g. Autism, PDD-NOS or Asperger’s) who are recently turned 3 years of age or younger to take part in research on comorbidity. The study involves a questionnaire on issues your child may have aside from those associated with ASD, like eating or sleeping difficulties. It’s the first study of its kind in Ireland so I’d really appreciate your help, if you have any questions please get in touch by email ei.yawlagiunnull@3mahgninnuc.t, and include your postal address if you would like to take part, thanks for your help,
Tracey
Weekly Round-Up
Just a few of the many articles on Autism that I found interesting this week.
A short while ago I linked up to an article describing the importance of maintaining good family health. This week I came across an article on Autism Through Jacobs Eyes that succinctly describes the gamut of emotions that parents may go through after receiving a diagnosis. I think that it’s important to recognise that these emotional responses may resurface over a long period of time and that it’s very important for the parents to get the support they need to be able to support the child.
(Some of the links in the above paragraph may require you to be a member of Facebook before you can read them).
Also in the news this week is another study of brain function in connection with Autism. New CMU Brain Imaging Research Reveals Why Autistic Individuals Confuse Pronouns (wow! what a title) reported on prnewswire.com describes how children on the spectrum, who confuse the pronouns “I” and “you”, may exhibit poor synchronization between parts of the brain at the front and the back. (Remember last week we had a study that described poor synchronization between the left and the right of the brain). However the article on prnewswire.com came in for some criticism from Autism NB for misrepresenting the results as applying to all autistic children while the study only looked at high functioning children. However that’s two studies in a relatively short period of time that indicate poor brain synchronization may play a part in autistic behavior.
Autism study downplays genetics
Just when I thought I understood along comes a study that throws some doubt on genetics being the primary factor in determining autism.
Let us know what you think.
Autism study downplays genetics as primary cause – American Medical News.