How Does Autism ‘miss’ One Twin
In identical twin pairs, there are cases where one twin does not develop an ASD and one does. What accounts for this? How did autism miss the unaffected twin?
This is an area where many theorize that environmental factors have come into play. Was the affected twin exposed to some environmental hazard? Possible environmental culprits are being explored by a number of researchers, as they investigate everything from air pollution to pesticides. Did some exposure turn a certain gene on or off, or have some other effect?
Another possibility is a difference in the birthing process. Did one experience some kind of trauma, such as oxygen deprivation, before, during, or after birth, that the other did not?
One fascinating idea being explored is that sometimes identical twins may be different because they did not share a chorion, which can be thought of as a sac beyond and surrounding the amniotic sac. Twins can have their own chorion, or share one. If identical twins did not share a chorion, then they have actually not shared the exact same environment in the womb. Will different ASD concordance rates be found for identical twins who did or did not share a chorion?5
As researchers continue to study simplex families , multiplex families , and both identical and nonidentical twin sets, the complex genetic and environmental picture in autism should become much more clear.
When Only One Twin Gets A Disease
Identical twins share the same set of genes, such as ones for thick eyelashes or a pointy nose as well as the genes that boost risk for diseases. But sometimes rheumatoid arthritis, cancer, or another malady strikes one twin and not the other. What leads to such seemingly capricious twists of fate?
New research comparing gene expression in pairs of identical twins in which only one twin has a disease is trying to answer that question, looking at how the environment or other factors interact with genes to increase disease risk.
One such study, published this month in the journal Arthritis and Rheumatism, has identified three new genes involved in rheumatoid arthritis. It could eventually shed light on the factors that trigger the disease in genetically susceptible individuals.
Many diseases are caused by a combination of environmental and genetic factors. In rheumatoid arthritis, for example, an allergen or virus might trigger in a genetically susceptible person the expression of genes that cause inflammation and other problems, says Eric Matteson, a rheumatologist at the Mayo Clinic in Rochester, NY.
Holoshitz is also planning further experiments. He wants to figure out, among other things, whether blocking the culprit genes can help to slow the pain and inflammation of arthritis.
Facts About Autism Treatment
There is not one single treatment for autism.
There is no known cure for autism.
Evidence-based psychosocial interventions like behavioral treatment and skills training programs can reduce difficulties in communication and social behavior.
These interventions provide a positive impact on the persons quality of life.
Many children affected by ASD also benefit from interventions such as speech therapy and occupational therapy.
Early and intensive intervention can provide optimal development and well-being for individuals with autism.
Early intervention can improve learning, communication, and social skills, while also boosting brain development.
During treatment, the development of the child should be routinely monitored through maternal and child health care support.
ASD interventions are complex and incorporate various techniques.
Applied Behavior Analysis and therapies based on its principles are the most researched and most commonly used behavioral interventions for autism.
Early interventions need to be personalized, based on individual childrens needs and learning styles.
Personalized and individualized interventions will yield the best results.
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Early Life Experiences May Shift Severity Of Autism
This article was originally published in May 2019 based on preliminary data presented at a conference. We have updated it to reflect findings published in Behavior Genetics1.
A childs environment exerts a strong influence on the severity of her autism, according to a study of 78 pairs of identical twins in which at least one twin has autism.
Researchers presented the unpublished results yesterday at the 2019 International Society for Autism Research annual meeting in Montreal.
Studies in identical twins have shown that autism has a strong genetic basis: If one identical twin has autism, the other one has it, too, as much as 90 percent of the time.
The new work supports these estimates: In 64 of the 78 twin pairs, both twins have an autism diagnosis. However, autism severity often differs greatly within the twin pairs. In one twin pair, for example, one boy is essentially nonverbal, whereas the other has excellent speech.
Its almost impossible to believe that identical twins can be so different its remarkable, says lead researcher John Constantino, professor of psychiatry and pediatrics at Washington University in St. Louis, who presented the findings.
The results suggest that the quality of life of autistic children is not hardwired by their genetics.
Study Debunks Autism As A Primarily Genetic Disorder
A rigorous study of nearly 400 twins has shown that environmental factors have been underestimated, and genetics overestimated, for their roles in autism-spectrum disorders.
The study found that the childrens environment represents more than half of the susceptibility 55 percent in the most severe form of autism and 58 percent in the broad spectrum of the disorder while genetics is involved in 37 percent and 38 percent of the risk, respectively.
This is the largest and most rigorous twin study to date to research the genetic component of the disorder, and tapped expertise from the UCSF Institute for Human Genetics and Stanford University which jointly led the research as well as from Kaiser Permanente, UC Davis, the Autism Genetic Research Exchange and the California Department of Public Health.
Autism had been thought to be the most heritable of all neurodevelopmental disorders, with a few small twin studies suggesting a 90 percent link, said UCSF geneticist Neil Risch, PhD, director of the UCSF Institute for Human Genetics and senior author of the paper. It turns out the genetic component still plays an important role, but in our study, it was overshadowed by the environmental factors shared by twins.
Findings appear in the Archives of General Psychiatry.
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Zeroing In On The Genetics Of Autism
Some evidence that genetics plays a role in autism and ASD is provided byresearch on twins. According to the CDC, if one identical twin has autism,there’s a 75% chance the other twin will be affected, too. If a fraternal twinis affected, the other twin has a 3% chance of having autism.
Parents who give birth to a child with ASD have up to an 8% chance of havinganother child who is also affected, the CDC estimates.
Many U.S. couples have delayed childbearing, and the older ages of both themother and the father have been linked with a higher risk of having childrenwith ASD, according to a report in the journal Pediatrics. With agecould come increased risk for genetic mutations or other genetic problems.
Specific genetic problems help explain only a small percentage of autismcases so far. “We know that major chromosomal abnormalities areidentified in about 5% of ASD,” says Milunsky of Boston University. “Weknow that Fragile X syndrome is responsible for about 3%.” Fragile Xsyndrome, a family of genetic conditions, is the most common cause of inheritedmental impairment, and also the most common known cause of autism orautism-like behaviors.
“Hot spots” of genetic instability may play a role, researchers say.For instance, a team of researchers reported in The New England Journal ofMedicine that duplications and deletions on a specific chromosome seem tobe associated with some cases of autism.
But genetics is not the whole story, he and other experts say.
Rosemond: Autism Diagnosis May Just Be Normal Twin Behavior
Q: I am a grandmother with custody of my two grandsons, 6-year-old twins. Because of behavior problems at home and school and difficulties relating to other children , they have been diagnosed with autism. What is your opinion of the diagnosis and what can I do to help them? Their therapist has told me that usual means of discipline wont work but has yet to give me something that does.
A: As opposed to a verifiable physical disease such as cancer, all psychiatric diagnoses, including autism or, more accurately, autism spectrum disorder are based not on “hard” data but on third-party description. As such, a diagnosis of ASD is a construct, and therefore subject to unreliability. One psychologist may render a diagnosis of autism while another may render, for the same child, a diagnosis of, say, childhood bipolar disorder or oppositional defiant disorder.
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There are several theories concerning autism that attribute its origin to genetics and other biological factors, but none of them have been proven conclusively. The dispute, mind you, is not over what people are reporting behavior but speculative notions regarding etiology, or cause.
What does not work with ASD kids is acting like the diagnosis requires that they be handled with kid gloves. The proper discipline of a child, diagnosis or not, requires adults who are ready to step up to the plate and deliver unequivocal authority.
Kid gloves just wont do.
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Twins And Autism Risk
For the study, researchers culled a California registry of children who receive services for developmental disabilities and identified 192 sets of twins in which at least one child had received a diagnosis of autism or other autism spectrum disorder, like Aspergerâs syndrome. There were 54 pairs of identical twins in the study and 138 pairs of fraternal twins.
Researchers used standard psychological assessments to confirm the childrenâs diagnoses.
To calculate the relative contributions of genes and the environment to autism risk, researchers compared the number of identical and fraternal twins in which both siblings had been diagnosed with the disorder.
Because twins share nearly all aspects of family life and environment, comparing identical and fraternal siblings allowed researchers to see how autism rates differed when the only variable that was different was the number of shared genes.
As expected, identical twins were more likely to share an autism diagnosis than fraternal twins.
What was surprising, though, was that both fraternal twins were diagnosed with autism more often than could be explained by genetics alone, suggesting that common environment factors were at work.
Researchers say that based on their models, environment may account for about 58% of the risk for autism spectrum disorders, with genetics accounting for about 38%.
âThereâs a big range of confidence on those statistics,â Goldsmith says. âThereâs no precision to those estimates.â
Another Clue In The Mystery Of Autism
- Northwestern University
- A study of discordant twins — twins in which one has autism spectrum disorder and one doesn’t — finds the lower birth weight twins are more than three times as likely to have ASD than heavier twins. Though genetic effects are of major importance, say researchers, the study suggests a non-genetic influence associated with birth weight may contribute to development of ASD.
Although the genetic basis of autism is now well established, a growing body of research also suggests that environmental factors may play a role in this serious developmental disorder affecting nearly one in 100 children. Using a unique study design, a new study suggests that low birth weight is an important environmental factor contributing to the risk of autism spectrum disorder .
“Our study of discordant twins — twin pairs in which only one twin was affected by ASD — found birth weight to be a very strong predictor of autism spectrum disorder,” said Northwestern University researcher Molly Losh. Losh, who teaches and conducts research in Northwestern’s School of Communication, is lead author of the study that will be published in the journal Psychological Medicine and is now available online.
The researchers found that lower birth weight more than tripled the risk for autism spectrum disorder in identical twin pairs in which one twin had ASD and the other did not.
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What Do We Know About The Shared Environment
We know that some medications, for example valproate, taken during pregnancy can increase the risk of autism. We also know that some infections, like a rubella infection during pregnancy, can increase the risk of autism. Beyond that, there are many suggested factors, but there is still much research needed to confirm those factors.
We are a long way from fully understanding the causes of autism. New studies are published every day, which add to our understanding. The information on this page is designed to give you an overview.
Twins Study Finds Large Genetic Influence In Autism
What plays a bigger role in autism, genetics or environment? Scientists don’t agree on the answer, but the debate just got more attention with the arrival of a new study involving twins. When you look at “extreme” autism symptoms, genetics plays almost the only role, according to that study, led by clinical psychologist Thomas W. Frazier II of the Cleveland Clinic.1
That conclusion in favor of genetics differs markedly from a 2011 twin study that found that the environment was a significant influence. In medical research, the environment usually refers to everything from the air you breathe to your parents’ ages when you were conceived and your prenatal conditions. The earlier study found that fraternal twins, who shared the same environment before birth but have different DNA, were more likely to both have an autism spectrum disorder than siblings who weren’t twins. That study look at 192 pairs of twins in California.2
Dr. Frazier had questions about the California study, so he decided to launch his own autism twins study, the largest of its kind so far. His team analyzed information about 568 pairs of identical and fraternal twins in the Interactive Autism Network database.1
Some researchers have assumed that autism is an extreme version of normal behaviors, just as Attention Deficit Disorder might be an extreme version of a normal tendency for someone’s attention to wander. Dr. Frazier said.
A 2009 IAN Twins study: Twins! A Key to the Mysteries of Autism
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Autism Diagnosis At Ron Joyce Childrens Health Centre
After being referred to McMaster Childrens Hospitals Ron Joyce Childrens Health Centre , both boys were formally diagnosed with autism spectrum disorder .
I remember crying after receiving the diagnosis, says Tom. We were both relieved and scared that we now had a name for their condition. Once we realized our journey with these boys was going to be different than expected, we set out to learn as much as we could to help them.
The family began attending Social ABCs, a program that teaches parents strategies to help their children interact and communicate with others. When the program ended, they were placed on a waiting list for additional services.
RJCHCs autism services are essential to the well-being and development of our boys. The team make our struggles their struggles. We trust our children with Hamilton Health Sciences because the therapists treat us like family.
After waiting as long as we could, we started planning to fund the services out of our own pockets, explains Tom. When the funding model changed in Ontario for autism services, we ended up being the first parents to pay for services at Ron Joyce Childrens Health Centre.
The boys were enrolled in Applied Behaviour Analysis Therapy and worked with therapists to build on communication skills and reduce behaviours like screaming and aggression.
Raising Twins Is Very Difficult How Is Raising Twins + One With Autism More Or Less Difficult
I believe that its a LOT more difficult raising twins when one has autism. I imagine that neurotypical twinsfunctioning at the same developmental levelinteract with each other more, and enjoy entertaining one another. Sibling rivalry is more painful and intense for both children when one twin has autism. In addition, parents of neurotypical twins are probably able to give each twin equal time. Children on the spectrum are much more demanding because of their special needs, sensory issues, rigidity and meltdowns that all takes more of the parents time and so does accompanying them to therapy. Neurotypical twins usually go to the same school. My twins went to different schools and camps for theirentire childhood, benefitting them but making logistics more difficult for my husband and me.
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Autism Only Moderately Follows Genetic Lines With Environmental Influences Weighing Heavily In Development Of The Disorder Researchers Found In A Twin Study
Autism only moderately follows genetic lines, with environmental influences weighing heavily in development of the disorder, researchers found in a twin study.Comparing fraternal and identical twins for autism incidence, shared environment appeared to explain 55% of the variance in strictly-defined autism and 58% in autism spectrum disorder, Joachim Hallmayer, MD, of Stanford University, and colleagues reported.Genetic heritability appeared to explain 37% of the variability for autism and 38% for autism spectrum disorder, the group noted online in the Archives of General Psychiatry.
- A new study of twins suggests that environmental factors, prenatal and postnatal, may be at least if not more as important as genes in causing autism
- Note that the data for ASD were very similar suggesting to those for strict autism..
Genetics may have gotten heavier emphasis in autism than it warranted, the researchers cautioned.
Prior studies appear to have seriously underestimated concordance in fraternal twins compared with the current findings, which would overestimate the influence of genetic factors on susceptibility, they noted.
This has skewed the research focus toward finding the genetic factors underpinning autism rather than potential environmental triggers or causes, they wrote in the paper.
Among these 404 twins, 242 met criteria for autism spectrum disorder, with 171 classified as autism by a narrow definition.