By guest blogger and Rodale.com advisor Philip J. Landrigan, Mount Sinai School of Medicine
According to The Centers for Disease Control and Prevention (CDC), between 2002 and 2006, the prevalence of autism spectrum disorder (ASD) has increased by 57 percent.
As I explained previously,[LINK] research has found genetic causes account for no more than 20 to 25 percent of all ASD cases. In fact, the U.S. National Academy of Sciences has reported that 28 percent of developmental disabilities in children may be caused by environmental exposures.
Ultimately, we believe that identifying an environmental trigger of ASD could be the path to prevention.
The Importance of Identifying the Environmental Contribution
When discussing the environment, it is important to remember that our definition encompasses a broad number of factors, including:
- Industrial and agricultural chemicals
- Physical agents (heat and radiation)
- Foods and nutrients
- Prescription drugs
- Lifestyle choices
- Socioeconomic factors
- Interactions between all of these parts of the environment
Since the environment is something we can change, understanding how it interacts with the developing brain can help create preventable measures to stop the increase of ASD. If we can identify how the environment is impacting our health, we can do something to improve our health, as Linda S. Birnbaum, PhD, Director of the National Institute of Environmental Health Sciences (NIEHS) pointed out at the 2010 meeting Exploring the Environmental Causes of Autism and Learning Disabilities.
Research in the Environmental Causes of Autism and Learning Disabilities
Thankfully, scientists are working to understand these interactions, leading a variety of large epidemiologic studies that are currently in progress. At our meeting, we heard from many of the principal investigators and top officials of these studies, including:
The CHARGE Study (Irva Hertz-Picciotto, PhD) One of the few large case-control studies looking at causes and contributing factors for autism
Hertz-Picciotto reported at least a 200 percent increase in ASD diagnosis in California due to a true increase in incidence, possibly due to an environmental factor. She also noted that the incidence of several other childhood disorders has dramatically increased during the same time period, which could be explained by a common set of exposures. Hertz-Picciotto also described some interesting, yet unpublished work:
- Proximity to traffic air pollution during pregnancy almost doubles the risk of autism, reports a new paper published in Environmental Health Perspectives.
- Unpublished research finds maternal antibodies to fetal tissue only seen in mothers of children with ASD. This suggests that prenatal inflammatory response to fetal brain tissue could cause a derangement in brain development—leading to or creating vulnerability for the development of ASD.
Study to Explore Early Development (SEED) (Coleen A. Boyle, PhD) A collaborative, multi-year, six-state case-control study funded by the CDC
SEED aims to better characterize the behavioral and physical characteristics of ASD, learn more about ASD comorbidities (the presence of one or more diseases or disorders, in addition to a primary one), and generate hypotheses regarding risk factors.
The EARLI Study (Craig J. Newschaffer, PhD) A project developed within the CHARGE study to bring back mothers of an autistic child who are now pregnant with a second or third child, to study prenatal and early neonatal risk factors
This study will track 1,200 mothers of autistic children as they experience subsequent pregnancy. Mothers—and their homes and families—will be tested for various exposures before, during, and after birth, and the younger sibling will be tracked for three years.
The National Children’s Study (Marion J. Balsam, MD) A longitudinal observational study that aims to enroll 100,000 subjects and follow them from the prenatal period to age 21
Unprecedented in scope and complexity, this is the largest long-term study in the U.S. to look at environmental effects on child health and development.
The Korean Autism Study (Young-Shin Kim, MD, PhD, MPH) A large-scale cohort study that examines gene-environment interactions
International research has the potential to uncover important environmental contributions, as genetics and environmental factors differ greatly worldwide. Researchers collect biologic, phenotypic, behavioral, and environmental exposure data on children with and without autism. The KAS is unique because of the Korean population’s genetic characteristics, defined by:
- An ethnically homogenous ancestral group.
- Minimal immigration and strong social pressures against non-Koreans.
- Rare consanguinity, meaning less shared genetic material.
The Norwegian Mother and Child Cohort Study (Christine Roth)
Highlighting additional international research, Ms. Roth introduced the Norwegian Mother and Child Cohort Study, which ran from 1999-2009. The study captured data on 107,000 pregnancies through questionnaires during and after pregnancy and is linked to national registries such as the birth registry.
Resources at the Mount Sinai School of Medicine
To conclude the workshop, we heard from our own researchers at the Mount Sinai School of Medicine, who described how their projects could be developed into studies that uncover environmental contributions to ASD. Presentations included:
- Latha V. Soorya, PhD, from the Seaver Autism Center, which conducts clinical, industry, and basic science research in Mount Sinai’s Department of Psychiatry.
- Stephanie M. Engel, PhD, from CEHC, who discussed her research on prenatal phthalate exposure and neurodevelopmental impairment.
- Patrick R. Hof, MD, a neurobiologist who is working to characterize regional, discrete, and cell type specific neuronal pathology in autism. He is using age‐ and gender‐matched autopsy brain specimens from people with autism to look at neuron morphology, focusing on a type of neuron thought to control the autonomic nervous system and related to the emotional aspects of human function that are affected in autism. This neuron appears to be abnormally distributed in the brains of people with autism.
- Luca Lambertini, PhD, from CEHC, who discussed the Mount Sinai Pregnancy Biobank, a cord blood and placental tissue repository that will be a valuable resource in studying prenatal exposures and child neurodevelopment.
The Way Forward
We strongly suspect that there is an environmental contribution to autism and learning disabilities. We know there is high likelihood that some chemicals have the potential to cause childhood brain injury that could result in autism and learning disabilities. Now we are working to reframe scientific conversation in this area.
Our next step is to use the information that we gathered at our workshop to create an action plan for discovery. Over the next months, CEHC will develop a prioritized list, outlining suspect chemicals that we believe are most likely to cause autism and learning disabilities. Since we lack the safety and toxicity data on thousands of synthetic chemicals—many of which can be found in the blood and urine of most people in the industrialized world—we know that this work is becoming increasingly crucial.
We believe that any progress we will make in unraveling causes of ASD will be multidisciplinary, including those who have been the core of both ASD research and clinical work.
Thus, we ended the workshop with the following conclusions:
- Unanimous consensus that the possibility of an environmental contribution to autism and learning disabilities warrants serious consideration and systematic investigation.
- Agreement that discovery of the environmental causes of autism and learning disabilities is going to be a multidisciplinary effort—combining epidemiological, laboratory, and basic science studies.
- Commitment to developing a prioritized list of suspect chemicals that we believe are those most likely to cause autism and learning disabilities.
- Importance of the Mount Sinai Pregnancy Biobank, which will play a crucial role as a platform for discovery of the environmental causes of autism and learning disabilities.