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Scientists Seek Early Indicators of Autism

September 27, 2007


By Walter Lerchner, Ph.D., California Institute of Technology

Autism Spectrum Disorder (ASD) is typically diagnosed around 3 years of age.



However, earlier diagnosis can go a long way toward optimizing outcomes by allowing application of early intervention techniques, as well as helping parents to obtain necessary services and the time to adjust to the special needs of their child. In the past few years, diagnosis at an age of 2 years has become more reliable, but this still requires that parents are aware of the early warning signs and seek out a diagnosis. Therefore, discovering methods that could predict the risk of developing autistic behaviors at a very early stage in life is extremely critical.

Even though the social impairments of the syndrome may not manifest until much later, scientists believe that the roots of some cases of ASD may be traced back to problems in the development of the fetus, due to a genetic predisposition and/or environmental factors. With respect to early diagnosis, this may mean that biological indicators that are caused by the same processes that lead to ASD may raise warning flags as early as the birth of the child. Some biological indicators previously identified in children with ASD include differences in brain structure and delayed development in the uterus. One problem with many of the proposed biological indicators for autism is that they are rather difficult to quantify or require expensive procedures to be determined. Moreover, many of the more well-characterized markers, such as increased head growth, are physical changes that are observed much later in development.

George Anderson, Ph.D., a member of the scientific advisory board of CAN and first author of a recent study conducted at Yale University, believes he may have found a promising new biological indicator by looking at the placenta, which is developed from the same cells as the fetus itself. After birth, the placenta can be examined without any intervention in the child or the mother.

Just like the developing fetus, the layers of the placenta are formed by an intricate pattern of cell division and cell migration. If cells forming a particular layer divide faster than the overlying layer of cells, "inclusions" (irregular cell clusters) can be formed that are readily detectable upon examination of the microscopic structure of the tissue.

In this preliminary study, 5 of 13 children with ASD had placentas with inclusions, while inclusions were found in only 8 placentas of 61 control children. If those numbers are confirmed in a larger study, the presence of inclusions in the placenta would represent a threefold risk of developing ASD later in life. Like other biological indicators, the inclusions may not be the cause of ASD but they could be the result of the same processes causing ASD. There have also been a few reports of neuropathological evidence of abnormal cell migration and cell positioning in the brains of some individuals with ASD, which may add support to these current findings.

Harvey Kliman, M.D., Ph.D., a senior author of the study, likens the presence of these inclusions to an automobile check-engine light. "When the light goes on it simply means that something is not right," said Dr. Kliman. "If the check-engine light is on and there is nothing obviously wrong, then the car should be carefully checked." In the case of inclusion in the placenta, it may simply mean that it may be prudent for parents to be on the lookout for signs of ASD.

While biological indicators, like placenta inclusions, can be used as early warning signs, they may also lead to a better understanding of how ASD develops. This in turn may lead to identification of more early biological markers for the syndrome. Eventually doctors may be able to use a combination of biological indicators, genetic and behavioral tests to make an early and accurate assessment of the risk of developing autistic behaviors.

Continuing in its goal to move autism research forward, CAN has developed a Biomarkers Initiative to promote research into early biological indicators. To learn more about CAN-funded work on early biological indicators of autism, see our Biomarkers Initiative page.

References:

Yale Press Release:
Peart, K. Key to Early Diagnosis of Autism May be in the Placenta. Yale University Office of Public Affairs.

Anderson G, Jacobs-Stannard A, Chawarska K, Volkmar F, & Kliman H. Placental trophoblast inclusions in autism spectrum disorder. Biological Psychiatry. June 26, 2006.