Causes of Autism: Are scientists getting closer?Heather Turgeon
It made headlines recently that kids with autism have a specific “fingerprint” in their urine – a set of chemicals released by bacteria in the stomach that is unique to children with the disorder. The results led some to speculate that a urine test for autism could be conducted in infancy, leading to earlier diagnosis and treatment.
Understandably, there was some buzz around the findings – it feels satisfying to read a study like this one and get the sense that scientists are getting to the root of the issue (in the same way that it felt like progress to hear that paternal age or IVF might be a contributing factor). Our ears perk up because we think it means the answer could be around the corner.
But the more I learn about the science of autism, the more I realize that our expectations about the hunt for its cause are out of line with reality. We’re waiting to hear conclusive evidence that wraps the problem up in a neat package, because most of us haven’t grasped just how complex the disorder and its biological underpinnings really are.
The recent findings from the Autism Genome Project are the best to date for understanding the full scope of the problem. Released earlier this month in the journal Nature, the high-profile research took place over a decade, involving 60 institutions and 120 collaborating scientists – the biggest, most detailed genetic study of the disorder so far.
Researchers analyzed the genomes of almost 1,000 individuals with autism and over 1,200 control subjects. They were looking for “copy number variants” – deletions or duplications in the DNA code that are suspected to underlie autism’s symptoms. They found that people with the disorder were 20 percent more likely to have these genetic hiccups.
The picture gets more complicated, though, because each affected person had a different variant in their genetic code – the changes were unique to each case. And to add another layer of complexity, many of the DNA alterations were not inherited from the parents, they were new – the children were the first in their families to have the mutations. The changes likely happened in the sperm or egg of the parents (before the children were conceived), say the scientists, as this is where gene variations commonly occur.
The good news is that the current study bolstered an existing theory of autism – that the disorder is related to changes in genes responsible for connecting brain cells. Many of the deleted and copied parts of the DNA code were indeed involved in this process of neuron communication. If scientists continue to hone in on these pieces of code, they will eventually understand the biochemistry of the disorder, and medical treatments could follow.
But even with an international consortium of scientists working for years on the most high-resolution study of autism’s genetics, the researchers say that they’ve only accounted for around 3 to 5 percent of gene changes that lead to autism. Speaking to NPR, the study’s lead author, Stanley Nelson of UCLA, said he believes that DNA changes will eventually be found to underlie almost all cases of autism. But the puzzle is so complex, it’s likely that hundreds of genes are at play.
In some ways, the progress is exciting – answers are building on each other and more markers for the disorder are being confirmed. With advancing technology to inspect the human genome, scientists seem optimistic that they can dissect the problem one step at a time.
For the general public, though, understanding autism is probably never going to have an “ah-ha” moment” – at least not any time soon. It’s an amazingly complex neurobiological disorder involving an intricate web of biological pathways.
To put it correctly, autism is actually not one disorder (it’s not even one disorder with varying levels of severity, as the term “spectrum” implies) – evidence points to it being many different disorders, each, in turn, with many different causes. Doctors group them together under one label because the symptoms fall into similar categories, like social skills impairments and repetitive behaviors. But this is only because the biological underpinnings are still largely a mystery.
In-depth genetic studies like this one put the issue in perspective and help set our expectations about the field’s scientific advances. For such an elaborate and varied disorder, we have to be ready to hear equally tricky answers.