Nieman: More research needed into origins of autism spectrum disorder

Over the past two to three decades, we have seen major developments in the diagnosis and treatment of autism. The term autism is rarely used these days. It has been replaced by three letters: ASD, or autism spectrum disorder. Experts who decide on terminology feel it is a better description of reality as this condition is indeed marked by a spectrum of presentations and severity.

ASD arises during early brain formation and the current incidence appears to be around 1 in 54 children. Male children are four times more likely to be affected than female children.

Diagnosing ASD accurately and early requires a vast amount of resources. It can become very costly and the demand for timely care often outstrips the capacity to provide delivery of this care. Thus, prevention may be a way to reduce the incidence and lower the overall cost for a condition that has become more prevalent over the past 20 years.

Although the exact cause remains unknown, we continue to discover more possibilities. A recent article in Pediatrics, the official journal of the American Academy of Pediatrics, considered toxic chemicals as one of the possible causes of autism. Researchers, led by a team at John Hopkins University, make a very good case that we need to be more concerned about the neurotoxicity of certain toxins.

The role of lead as a neurotoxin historically raised one of the first red flags. Since lead was discovered as a neurotoxin, thousands of other environmental chemicals and toxins have been discovered. When it comes to ASD, the role of toxins inflicting damage during early brain development requires more in-depth research. In animal models, there is a greater degree of certainty that toxins do play a role as a cause for ASD.

Scientists have found that air pollution exposures during pregnancy and early infancy, at levels typically found in large cities, are associated with autism.

Gestational exposure to pesticides may also increase the risk of causing ASD. Specifically, organophosphates and organochlorines have been implicated.

Chemicals known as endocrine-disrupting substances also have been implicated in terms of being associated with a higher risk of ASD. Phthalates, a ubiquitous chemical, causes a decrease in testosterone. According to the Johns Hopkins study it has been implicated in the etiology of autism.

The authors of the research paper agree that the dance between genes and the environment remains very complex, but they also suspect that the role of genes has been inflated and the role of the environment remains under-appreciated.

To show the complexity of this “dance”, researchers looked at over 10,000 chemicals and how they may impact genes and genetic pathways. They discovered that 4,428 chemicals interacted with one or more of the genes linked to autism.

They argue that, as with other conditions that have multiple factors, it is highly?likely that the interplay of gene variants and environmental factors contributes to a substantial proportion of ASD.

What the authors seem to suggest is that we know there is smoke and thus there has to be a fire, but at this time, the extent of the fire is uncertain; more research is needed. Meanwhile, governments should not allow new chemicals to enter the market unless they have been tested for developmental neurotoxicity.

Regulation must be based on data obtained through proper research. To improve the quality of current research, more funding is required; more collaboration between various silos of researchers must be formed, and a full-scale commitment to identify offending toxins needs to be established. This task will remain as difficult as changing the direction of a big ocean liner – it will take much time and a deeper level of advocacy.

The good news is that we know how important it is to ensure folate supplementation from the very start of any pregnancy. By doing that, the impact of toxic chemicals can be greatly ameliorated.

In another article, also published in Pediatrics, researchers from the Mayo Clinic in conjunction with the Autism and Developmental Medicine Institute in Pennsylvania and the College of Medicine at Baylor University in Texas wondered if it may be possible that we have underestimated the IQ of children with ASD.

The quality of their research was impressive – it involved a large longitudinal population-based cohort. The interesting conclusion is that there is an increased rate of average to above-average intelligence among individuals with ASD. The data suggested that nearly half of individuals with ASD have an average or higher IQ. The Mayo Clinic experts express concern that unless IQ tests are done on children with ASD, children with average to above-average IQs will not be identified. This failure may cause long-term adverse effects such as not developing meaningful relationships and an inability to maintain employment.

Dr. Nieman is a community-based pediatrician in private practice. He is an author, marathon runner and the former president of the Alberta chapter of the AAP.