Today’s question came in response to my last blog post. In it, I explained that when scientists talk about the “environmental factors” that increase the risk of a disorder, they’re referring to pretty much any influence beyond genetics.
In the case of autism, the clearest evidence of environmental influence seems to surround very early events such as conception, pregnancy and birth. Those with the strongest link include parental age at time of conception (both mom and dad), maternal nutrition or illness during pregnancy, and certain birth complications.
The commenter’s question is a great one that scientists are actively exploring. The short answer is that inherited genes (DNA) and environmental factors seem to interact to influence whether an infant goes on to develop autism. So if the commenter’s twins are fraternal (meaning they share about half their DNA), the difference in their genetic makeup might explain why only one developed autism.
But what if the boys are identical twins–meaning they share exactly the same DNA? In this case, something beyond genes likely accounts for the different outcomes. Comparing the rates of autism among identical and fraternal twins provides clues.
In July, researchers used our Autism Genetic Resource Exchange (AGRE) to complete the largest autism twin study to date. They found a 70 percent overlap in autism among identical twins and a 35 percent overlap among fraternal twins. That overlap between fraternal twins is much higher than the estimated 19 percent overlap between different-age siblings.
These numbers tell us that it’s not always genes alone that determine whether a child develops autism. If it were, two identical twins would always share the same outcome, and the rate of a shared autism among fraternal twins would look more like that for different-age siblings. So we conclude that shared environmental influences are also at play.
Although twins share very similar pregnancy and birth environments, those environments aren’t exactly the same. For example, twins can have different positions in the womb or different placentas, and this can affect such environmental influences as blood and oxygen flow. Indeed, twins often have different birth weights, a known risk factor for autism.
It’s important to remember that “environmental” influences such as these don’t cause autism by themselves. Rather, if a child has a genetic predisposition for developing autism, these influences may further increase the risk.
Autism Speaks continues to fund and otherwise support research on both genetic and nongenetic risk factors for autism. EARLI is a network of researchers who follow mothers of children with autism beginning at the start of another pregnancy. IBIS is a study of early brain development in the younger siblings of children with autism. These studies depend on the participation and support of the autism community. Please visit our Participate in Research page to learn more.
Importantly, these studies provide insights into the underlying biology of different types of autism. This in turn becomes a basis for developing ways to treat and possibly prevent autism. As always, the goal of the research we support is to improve the lives of all on the autism spectrum.
And thanks for the question. Please keep them coming.
Autism’s recurrence within families is of tremendous interest to both researchers and families, and our “High Risk Baby Siblings Research Consortium” continues to study this and other important questions regarding the risks, causes, prevention, and early treatment of autism.
We support this research consortium in collaboration with the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). In 2003, Alice Kau, of NICHD, and our own VP of Scientific Affairs Andy Shih organized the consortium. I joined with a leadership role in 2005. Since then, the group has grown to include 25 leading autism researchers across 21 medical centers in the United States, Canada, Israel, and the United Kingdom.
They all share the goal of studying the earliest symptoms of autism spectrum disorders (ASDs). They are able to do so because of the generous participation of families with infants and at least one older child on the autism spectrum. These families are so important to research because of the relatively high likelihood that autism will recur among younger siblings.
By following the development of these young children, our consortium researchers are able to do much more than give us more accurate information on recurrence rates. For example, they are making exciting progress in increasing understanding of how and when autism signs and symptoms first appear. This includes insights into the pattern we call “regression,” which involves a loss of skills in an infant or toddler who appeared to be developing normally. As a group, the consortium has published a number of articles to help guide pediatricians and other primary care doctors in how to approach children and families already affected by autism. Their research into early signs and symptoms, for example, has helped clinicians diagnose and provide treatment as early as 12 months of age.
Several of the Baby Sibling Consortium researchers also participate in another important Autism Speaks group, the Toddler Treatment Network. It has a deeper focus on early signs and symptoms, particularly as they relate to developing earlier interventions that may actually prevent the development of some or all autism symptoms.
Families with recurrent autism are crucially needed to help our researchers identify the genes and other influences that increase the risk that children will develop autism. By allowing our researchers to track progress beginning in pregnancy, for example, families provide insights into such risk factors as parental age at conception, and maternal infection and nutrition during pregnancy.
Our researchers are also tracking brain development and identifying so-called biomarkers (such as distinctive brainwave patterns) for earlier and more accurate diagnosis. And, yes, this research can also help us look at whether certain patterns of vaccination make any difference in the risk of autism among children genetically predisposed to the disorder.
Taken together, a better understanding of early signs and symptoms has led to earlier, better accurate diagnoses of ASD along with important knowledge of what causes autism. This research is not possible without the group working together, and without the valuable support of the National Institutes of Health, and most importantly, the families who donate their valuable time to this research.
Interested in learning more—and perhaps participating in the research? Please check out our list of Baby Sibling Research Consortium researchers and contact one in your area.
With the release of the first major report of the Autism Speaks Baby Siblings Research Consortium, the world learned that the autism recurs in families at a much higher rate than previously estimated. For perspective and guidance, the national media turned to our director of research for environmental sciences, Alycia Halladay, PhD.
Vodpod videos no longer available.
Autism Speaks’ Alycia Halladay, Ph.D., provides perspective on NPR’s All Things Considered. To listen to the segment, visit here.
The CBS Early Show aired, ‘Study suggests link between Autism, siblings’ that can be viewed here.
For Siblings of Autistic Kids, Risk Is Far Higher Than Thought (TIME)
Autism runs in families to a much greater degree than previously thought, according to new research that has tracked the younger siblings of children with the developmental disorder. Read more.
Chance of having more than one autistic child higher than thought (MSNBC)
Siblings of kids with autism have a higher risk of being diagnosed with the disorder than previously believed, suggests a new study. Read more.
Autism Risk for Siblings Higher Than Expected (The New York Times)
Parents who have a child with autism have about a 1 in 5 chance of having a second child with autism, a far greater risk than previously believed, new research shows. Read more.
By Geri Dawson, Chief Science Officer, Autism Speaks
Last week, a paper was published in Pediatrics that argued against the routine screening for autism by pediatricians. Three investigators who are part of the Autism Speaks Baby Siblings Research Consortium and I submitted a letter to the editor in response to this paper, which has now been published. The link to the original article and the letter are provided below. Our letter provides a strong rationale and empirical evidence to support the American Academy of Pediatrics recommendations that all children be screened for autism at their 18 and 24 month checkups.
This exchange highlights the important role of the scientific research in directly influencing policy and clinical practice. We were able to cite research, much of which was conducted by Autism Speaks Baby Siblings Research Consortium investigators, to counter the inaccurate statements by the authors of the Pediatrics paper.
In 2007, the American Academy of Pediatrics published guidelines recommending that all children be screened for autism at their 18 and 24 month well baby checkups. While these recommendations have not been universally implemented in clinical practice, these guidelines are a positive step forward. New research from the Baby Siblings Research Consortium suggests that signs of autism can be detected as early as 6-12 months. Early detection and subsequent early intervention provide hope of changing the developmental trajectories of children with ASD to improve their outcome.
A recent study published in the Journal of Pediatrics, and supported by Autism Speaks, aims to address each of these challenges by utilizing a checklist called the Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist. Lead author Karen Pierce, Ph.D. of UCSD asked pediatricians to use this instrument as part of a well-baby checkup. This checklist was developed by Amy Wetherby, Ph.D., who was instrumental in creating the Autism Video Glossary. The instrument is also available online at www.firstsigns.org.
The researchers took a multi-phase approach. They first provided training to pediatricians on the signs and symptoms of autism. Such an approach has been used successfully before by a group at Vanderbilt University. However, this study screened infants as early as 12 months of age and conducted the 1 year screening in pediatricians’ offices, which had not been done before. Next, parents were asked to fill out the questionnaire in the waiting room, and the questionnaire was scored by the time the parent met with the physician. The checklist responses from parents then were reviewed by participating pediatricians, and children who were flagged by the questionnaire were referred to a UCSD clinic for further evaluation. About 12% of children who were screened were referred to the clinic for an evaluation. Of those, about half were followed to 3 years of age and 17% were later diagnosed with an ASD. Other diagnoses included learning disabilities and developmental disabilities.
This study is important for several obvious and some not so obvious reasons. First, and perhaps most importantly, this study shows that it is feasible for pediatricians to become actively engaged in an easy-to-implement early screening program for ASD for children as young as 12 months of age. Also important, all families who were interested were able to obtain the services of a clinician very early in their child’s development. For those that were later diagnosed with an ASD, 100% received treatment by 17 months.
Second, a training program that increased awareness about ASD in the medical community among pediatricians produced a long-term impact on their practice. Only 22% of pediatricians involved were screening for autism at 1 year before the program; now all of them report they are maintaining the use of the toddler checklist.
However, this method is not without its limitations. The effectiveness of this program depends on the ability of pediatricians to have access to and a relationship with a clinic they can refer to, which is not the case in every area of the country or the world. Also, not all infants who were referred went on to receive an evaluation, for reasons that are unclear. The results suggest that early screening may enhance, not replace, evaluation at 18 and 24 months to ensure that cases that may not be detected as early as 12 months are not missed.
We applaud the work of Pierce and her colleagues for their efforts to identify autism as early as possible and bring primary medical care staff into that process. Studies such as this highlight the many very important steps, undertaken by the Baby Siblings Research Consortium, the Autism Treatment Network and the Toddler Treatment Network, to ensure that children are screened as early as possible, seen by a clinician as part of a full evaluation, and then treated by trained personnel for medical and behavioral interventions. Additional efforts should be made to ensure that parents have access to a knowledgeable pediatrician and are provided with the resources to follow up on the recommendations.
Karen Pierce, PhD, Cindy Carter, PhD, Melanie Weinfeld, PhD, Jamie Desmond, MPH, Roxana Hazin, BS, Robert Bjork, MD, and Nicole Gallagher, BA. Detecting, Studying, and Treating Autism Early: The One-Year Well-Baby Check-Up Approach, J. Pediatrics, 2011 (published online April 28, 2011).
In honor of the anniversary of Autism Speaks’ founding on Feb 25, for the next 25 days we will be sharing stories about the many significant scientific advances that have occurred during our first five years together. Our fifth item is Diagnosis at 14 Months.
In a study in the Archives of General Psychiatry, researchers from the Kennedy Krieger Institute in Baltimore, Maryland found that autism can be diagnosed at close to one year of age, which is the earliest the disorder has ever been diagnosed. The study, which evaluated social and communication development in autism spectrum disorders (ASD) from 14 to 36 months of age, revealed that approximately half of all children with autism can be diagnosed around the first birthday. The remaining half will be diagnosed later, and their development may unfold very differently than children whose ASD is diagnosable around the first birthday. Early diagnosis of the disorder allows for early intervention, which can make a major difference in helping children with autism reach their full potential
Researchers examined social and communication development in infants at high and low risk for ASD starting at 14 months of age and ending at 30 or 36 months. Half of the children with a final diagnosis of ASD made at 30 or 36 months of age had been diagnosed with the disorder at 14 months, and the other half were diagnosed after 14 months. Through repeated observation and the use of standardized tests of development, researchers identified, for the first time, disruptions in social, communication and play development that were indicative of ASD in 14-month olds. Multiple signs indicating these developmental disruptions appear simultaneously in children with the disorder.
The current study reveals that autism often involves a progression, with the disorder claiming or presenting itself between 14 and 24 months of age. Some children with only mild delays at 14 months of age could go on to be diagnosed with ASD. The researchers observed distinct differences in the developmental paths, or trajectories, of children with early versus later diagnosis of ASD. While some children developed very slowly and displayed social and communication abnormalities associated with ASD at 14 months of age, others showed only mild delays with a gradual onset of autism symptoms, culminating in the diagnosis of ASD by 36 months.
If parents suspect something is wrong with their child’s development, or that their child is losing skills during their first few years of life, they should talk to their pediatrician or another developmental expert. This and other autism studies suggest that the “wait and see” method, which is often recommended to concerned parents, could lead to missed opportunities for early intervention during this time period.
To read the complete story, including the signs of developmental disruptions for which parents and pediatricians should be watching, please click here http://www.autismspeaks.org/inthenews/landa_study.php.
Update since this story was run: Members of the Baby Siblings Research Consortium, a collaboration between Autism Speaks and the National Institute of Child Health and Human Development, have now published multiple scientific studies demonstrating that early signs of autism can reliably be seen as early as 12-14 months of age. This improved understanding of the early signs and symptoms of autism has permitted development of new measurement tools to both quantify and diagnose autism symptoms earlier than ever before. For example, the Autism Observational Scale for Infants or AOSI was published by Autism Speaks’ grantees in 2008 and is currently a part of many protocols involving early autism diagnosis and intervention. It has been shown to accurately detect autism as early as 12 months of age. In addition, a modification of the ADOS, called the ADOS-t, was released in 2008 to enhance the clinical diagnosis of autism, indicating a range of concern for children as young as 12 months of age. Both tools are huge advances in the field of diagnosis, allowing for reliable early detection and placement in appropriate intervention services.