“[Blank] doesn’t cause autism.” It’s a common refrain. Yet no one seems to have answers for what does cause autism. I believe one major reason for this is that there isn’t one thing that causes autism.
Autism Isn’t a Disease
First of all, autism isn’t exactly a “disease,” per se. It’s more accurately described as a “syndrome” — a cluster of specific symptoms. That means saying someone has autism is somewhat akin to saying someone has a headache. It tells you how the body is responding, but it doesn’t describe a virus or bacterium or something of that nature.
If you have a headache, that might be due to a cold or the flu, dehydration, tension in your jaw, because you banged it on a door frame, etc. Likewise, autism is a description of what the body is doing, not why it’s doing it.
One Mechanism, Multiple Triggers
It’s probable there is one single mechanism behind autism. That single mechanism, however, might have a variety of triggers.
By way of illustration, consider mold in sheet rock. We can say that sheet rock molds because it gets (and stays) wet. Every time sheet rock molds, it was wet. But there are many ways the sheet rock might have gotten wet. Maybe it’s in a bathroom that has no ventilation and gets very damp. Maybe a pipe broke and water ran down inside the wall. Maybe excessive rain seeped in from outside. Maybe someone spilled something on it.
If 98% of moldy-sheet rock cases result from leaky pipes*, that doesn’t negate the fact that flooding from a hurricane can cause moldy sheet rock. It isn’t about sheer numbers; it’s about what can trigger the mechanism.
In similar manner, what triggers the type of inflammation that causes autism may vary from individual to individual, but that doesn’t make any one scenario less real than another.
*That isn’t an actual statistic; I made it up for the sake of our illustration.
Triggers Might Be Multifactorial
With both of those points in place as a foundation, we come to the biggest challenge of all: it’s very likely that autism can be multifactorial, triggered by a series of events.
Think about wind blowing a tree. Sometimes a strong wind blows a tree over, pulling it right out of the ground. But every tree doesn’t fall over in a strong wind, right? The age of the tree matters — how long it’s had to develop roots — as well as the weather conditions over the earlier course of the tree’s life. Those that have developed deep roots will be more stable than those that haven’t. The overall size of the tree matters. The type of soil it’s planted in matters. If it’s been raining a lot and the ground has softened up, that matters, too. Any or all of these factors combined can result in a tree that falls, rather than stands, when that strong wind comes along.
This type of complex “layering” of factors is very difficult to study, because every combination might be a little different. To return to the tree analogy, maybe one tree has weak roots, so the strong wind alone is enough to blow it over, while another tree has very strong roots, so it holds up well under wind unless it’s been raining heavily for days when the wind comes.
Let’s consider what this might look like when it comes to autism research. A number of contributing factors have been proposed for autism, with scientifically plausible reasoning. These include vaccines, ultrasound, genetic predisposition, and disruption of the gut flora. Let’s assume, for the sake of argument, all of these are valid. (You don’t necessarily have to agree that they are in reality; just allow them for the sake of illustration.)
If, then, someone were to study a vaccine to see if it results in an increased incidence of autism, how would the researchers control for what ultrasound(s) a child had been exposed to (how often, how long, at what developmental stage, and at what intensity), his personal genome, whether he’s had antibiotics, which other vaccines he has or has not had and when? Even for the most honest and conscientious researcher, this is simply a formidable task.
But if autism is multifactorial, this is exactly the type of research that needs to happen if we want concrete answers to “what causes autism?”