Redirecting autism research
Researchers and activists join together to discuss the direction of future research on the link between autism and the environment.
One in 150 children in the U.S. has autism, according to the Centers for Disease Control and Prevention (CDC). Decades ago, that number was thought to be about 5 out of 100,000. As more and more children demonstrate autismlike symptoms, their parents are asking whether environmental exposure to chemicals, such as mercury in vaccines, is causing the disease. In April, the U.S. Department of Health and Human Services called a meeting to explore a path for research on the broader impacts of environmental factors on autism.
A diverse group of scientists, activists, and caregivers attended the multidisciplinary meeting on autism and the environment, hosted by the Institute of Medicine (IOM). In recent years, parents and activists have pressed CDC to declare the rise in autism cases a public-health emergency. The meeting brought to the table new voices, who introduced lessons learned from investigating the origins of other vexing diseases, including asthma and schizophrenia. The meeting could impact the spending of funds that Congress earmarked for autism research for the first time last fall. That funding would provide $945 million over 5 years if Congress appropriates it.
The causes of autism, which slows down the development of young children’s social and communication skills by affecting the central nervous system, have remained elusive. Autism research has focused on genetic causes or on one compound that could be inflicting harm. The main suspect, in the minds of many activists and parents, has been thimerosal, the mercury-containing vaccine preservative that has generated controversy over the past several years. Some, including both researchers and activists, suspect food preservatives, pesticides, and a variety of chemicals.
Even the apparent increase in the number of autism cases in the 1980s is itself a controversial topic. As doctors’ knowledge of the disease grows, they may be likely to recognize it, so the increased number of cases may be at least in part a result of better reporting by physicians.
The variability in the manifestations of the disease has led to a shift in its name, to autism spectrum disorders, to cover the variety of symptoms. It is also leading researchers to search for an array of causes and triggers, much like the cancer research community started to do decades ago, says IOM forum participant Isaac Pessah of the University of California, Davis.
“If you think there’s no environmental contribution to autism, which was sort of the mind-set 10 years ago, it is limiting,” says Pessah. So, now that researchers have discovered some of the genetic ties indicating who might be susceptible to the disease, the search is well under way for specific windows during development, such as the formation of the auditory cortex, when single compounds or mixtures of compounds might trigger autism.
Teasing out the different mechanisms and timing can only happen with broad databases, participants at the meeting agreed. Many are looking to the Danish National Birth Cohort as well as the new Autism Birth Cohort (run by the Norwegian Institute of Public Health and Columbia University) and the CDC’s new National Children’s Study. All of these projects will provide data about behavior, and some have collected and stored tissue samples of expectant mothers and their children, including cord blood samples for the National Children’s Study.
CDC’s Larry Needham said that current biomonitoring includes a targeted approach that searches for exposures to preselected chemicals, such as PCBs, polybrominated diphenyl ether flame retardants, and the plastics component bisphenol A (tracked by parts of the National Health and Nutrition Examination Survey, or NHANES). However, because the cause of autism is unknown, Needham noted that a broader analytical approach should be developed that identifies several chemicals and their concentrations in blood and urine. But mining the data remains complicated with regard to the timing of exposure, especially for nonpersistent chemicals.
More than just data on chemicals is needed, workshop participants noted, listing animal models that can be compared with humans, geospatial data tracking of organophosphorus pesticides and other chemicals, and the need to revisit medical data and twin studies. Some participants seemed inclined to the pursuit of a concerted, centralized research program, much like the multipronged attack led by the Cystic Fibrosis Foundation, established in 1955, which marries research to clinical care.
IOM expects to release a summary of the discussions later this year. Meanwhile, worried parents and researchers alike are waiting to see what Congress decides next on funding levels for autism research.
