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.
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
Weekly Round-Up
One thing that never ceases to amaze me about the autistic spectrum is the huge amount of research, theorizing, speculation that’s published each week on the subject. I think it reflects how little we really do know about the condition from one end of the spectrum to the other.
While genetics are thought to play a role in autism there’s also a lot of people who will argue that the large rise in autism diagnoses has to be due to some environmental factor. I found an article, ‘Environment’ Poses a Knotty Challenge in Autism, that gives an interesting discussion on what ‘environment’ means in the context of autism.
When I was in my early 20′s (a looooong time ago) any discussion around becoming a parent would usually visit the topic; to vaccinate or not to vaccinate. This related to the research put forward by Dr Andrew Wakefield who suggested a link between the MMR vaccine and autism. Dr Wakefield’s research has since been thoroughly discredited; but his legacy lingers on in peoples minds and I get the feeling that researchers may be reluctant to reopen the vaccination debate. However Helen Ratajczak has undertaken a review of a wealth of credible published scientific research that suggests that vaccines may, indeed, play a part in the development of autism. There’s further comment in How to Help Eliminate the Hidden Enemy that Triggers Autism where it’s argued that a vaccine may act as a precursor to other events leading up to the autistic condition.
So the debate continues as we try to unravel the autistic spectrum. How many of you think that environment or vaccines have a significant role in the development of autism?
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
Wander Lust
Years before we ever considered autism as a diagnosis for our daughter we were greatly disturbed by her tendency to “wander off”. Actually it was more like she’d just vanish, one second she was right beside you, the next – gone.
This all have started about the age of 2. As soon as she could walk she refused to go into the push chair and so she’d be on foot whenever we went out. Large department stores were her favorites for doing a disappearing act. You’d only have to look away from her for a second and she’d be gone. The next few minutes would be spent in panic trying to find her, never sure if she been snatched or was just around the next rack of dresses.
Nothing we could say to her would stop her from wandering.
When she was about 3 we were all outside the house doing a bit to the garden – next second she was gone. Fortunately we were half a mile from the nearest road; but the terrain was wild and mountainous. After a few minutes frantic tearing over the land we found her down our track; I’ll never forget the sensations of fear as every possible scenario went through my mind.
So we moved to a more cultivated part of West Cork. The day after moved in she vanished again, this time we were living on a road! I went one way, the wife the other. She was in the field next to the house chasing the cows up and down. Fortunately the farmer had passed the field minutes before and stopped to find out why the cows were charging about. He rescued her from likely being trampled.
Next day she did it again. This time we knew where to look.
Day 3 she tried again; but this time got stuck on the fence and fortunately that put her off her cowgirl wanderings.
Where’s all this reminiscing leading? A survey has been conducted in the US and preliminary results indicate that this is a common phenomena amongst children on the spectrum and that age 4 is where this behavior peaks. This certainly fits with our experience. The preliminary results of the survey have been published on the Interactive Autism Network Community website and are well worth a read. The survey also looks at the reasons children might wander and also the effects this has on the parents. If we’d known this was a symptom of autism back then we might have got our diagnosis many years earlier than we did.
Our little ‘un is fast approaching her teenage years. She still wanders; but now we can be pretty sure she’ll be in the DVD or video game section of the shop so we know where to look.
What are your wander lust stories? How have you coped with this frightening aspect of autism? Please leave us a comment.
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.
Biological Marker For Autism
Copyright © Dr L Dinstein
An interesting report has been published in the Neuron journal that may indicate a means to accurately diagnose autism in very young toddlers.
The technique involves measuring the synchronization in electrical activity between the left and right hemispheres of the brain while the child is asleep. In children with delayed language development or a-typical development they found poor synchronization in the electrical activity between the left and right hemispheres. This was not evident in children with normal development nor in children with a language delay not associated with autism.
Imagine an orchestra were ready to play a piece of classical music and one half started a fraction of a second after the other half. What you’d end up with was a noise from which you could occasionally catch part of the melody. This could be similar to what’s happening in an autistic child’s (or adult’s) brain.
The Weizmann Institute reports that the researchers were able to diagnose 70% of autistic children aged 1 – 3 years old. This could form the basis of an empirical diagnosis of autism from a much earlier age than is currently possible.