From Autism Speaks' Blog: Got Questions?
Wednesday, April 18, 2012
What’s the difference between something causing autism versus increasing risk for autism?
Today’s “Got Questions?” answer comes from Martha Herbert, Ph.D., M.D., a pediatric neurologist and neuroscientist at the Massachusetts General Hospital, Harvard Medical School, a member of the Autism Speaks Scientific Advisory Committee and the author of the recently published The Autism Revolution: Whole Body Strategies for Making Life All It Can Be.
The search for the causes of autism is challenging because many things are risk factors – and yet when examined by themselves no one of them has the power to be labeled the sole “culprit.” Asking the question a different way might help. I think we need to ask, “How is autism caused?” I want to propose that genes and environment lead to autism by an accumulation of “Total Load” – a pile-up of risk factors to the point of overflow.
A case in point is the recent information implicating maternal obesity and diabetes as risk factors for having a child with autism. Clearly many or even most mothers of children with autism were not obese or diabetic during pregnancy. So this is obviously not the sole cause of autism. But that does not erase the finding. For women with these conditions, the study suggests that the diabetes or obesity might have had something to do with the autism that their child developed.
So let’s ask the “how” question: How could diabetes or obesity contribute to autism? The study’s title – “Maternal Metabolic Conditions and Risk for Autism and Other Neurodevelopmental Disorders” – points in an important direction. To understand why this choice of words is important, we need to understand what “metabolism” is and what happens when it gets into trouble.
Everything in our bodies involves biochemistry and physiology. Every microsecond, each of our cells is buzzing with innumerable chemical reactions and processes – building things up, breaking things down and sending messages. This is “metabolism.” Any glitches can make the operation get clumsy.
Genes can cause glitches in metabolism, and so can “environment.” Toxins can change metabolism – by blocking it, by revving it up, by confusing it. Sometimes the impact is subtle – but our bodies are dealing with lots of impacts all at the same time. The sum total of all environmental impacts – subtle and not so subtle – can be called “total load.” By “environment,” we scientists mean non-genetic influences, which can include such factors as maternal health during pregnancy and birth complications, not just toxic chemicals.
Think of it this way. We each have our own barrel that slowly fills up with noxious environmental exposures. Genes shape how much it can hold and how strong its walls are. So does the food we eat. A big barrel with strong walls can tolerate a lot, but a small barrel with thin, rusty walls is going to overflow and leak much more easily.
“Total Load” offers a good explanation of how people get diabetes or obesity – and these days so many people have both at once that it’s simpler to say “diabesity.” Diabesity is a metabolic condition, but when you dig below the surface, there’s a lot more to it than “a problem with insulin” or “too much fat.” From a “systems biology” viewpoint, diabesity can be understood as the end result of a long process of metabolic deterioration caused by an ever bigger “total load.”
Years of storing toxic exposures in our bodies gums up our metabolism. And years of nutrient-depleted processed food can produce deficiencies in the vital antioxidants and minerals we need to protect ourselves. By the time someone develops diabesity, it’s way more than eating too much. The whole metabolism handles calories differently.
In some people, “diabesity” is what happens when the Total Load overflows the barrel. In others it is autoimmune disease and in still others it is cancer. How it turns out for each of us probably depends on our genes, the toxins to which we’ve been exposed – and our diets, exercise and other lifestyle factors.
But underneath there are some commonalities. Indeed, many chronic conditions share underlying “metabolic” problems such as impaired energy production in the mitochondria, oxidative stress and inflammation. (You can read a variety of relevant research studies here.)
There is by now a large literature implicating these inflammatory, oxidative stress and mitochondrial metabolic problems in autism. This, too, implicates environment as well as genes.
The problem with metabolic compromises is that the more things go wrong, the easier it is for them to get worse. You slide downhill for a while but then you hit a tipping point, where your system gets stuck in a place we call “disease,” and it’s really hard to extricate yourself. It turns into a vicious circle. This may be what happens when someone slips from “insulin resistance” into “diabetes.”
It may also be what happens when a small child regresses into autism.
Which brings us back to the How question – How is autism caused? In The Autism Revolution: Whole Body Strategies for Making Life All It Can Be, I explain this in more detail through the stories of people with autism who got worse and then got better. But in brief, you can make a working model of autism as a different way of brain functioning that emerges when the Total Load exceeds the brain and body’s capacity to compensate.
Even better, this “Total Load” model can point you toward practical, everyday ways of reducing this Total Load now, while we wait for more detailed science to develop.
So then, how might diabetes or obesity contribute to a baby developing autism? Perhaps by accelerating the baby’s accumulation of Total Load. A mother with diabetes or obesity is short on antioxidants and has too many inflammatory factors – and these problems get passed on to the fetus. This does not in itself cause autism – but it may prime the baby for future trouble by making it more reactive to further stresses, and by failing to prepare it for these challenges with a good store of protective nutrients. The baby’s barrel is small, and its walls are thin.
If you look at it like this, diabetes and obesity are among the many ways that environment can create autism risk for a baby.
Risks don’t “cause” autism. But they may very well lay the groundwork for the tipping point when the Total Load becomes too much and the barrel starts to overflow and leak. The metabolic disturbance that started in adolescence or adulthood for the mother might start in infancy or even before birth for the baby.
Obviously this is a model. It strings together a lot of different observations into an interpretation, or story, that science can only test piece by piece. But there is no escaping models – we all use them whether we know it or not – and a big advantage of this Total Load model is that right now you can reduce the Total Load of your child by making their barrel stronger through eating a a high nutrient density unprocessed plant-based diet, getting regular sleep and exercise, and eliminating as many noxious exposures as possible. You can do this for yourself too, before your next pregnancy. This won’t be a quick fix for autism, but it’s certainly a foundation for making life as good as it can get under the circumstances.