Is autism getting more common, or does it just look that way?

Last year I participated in the Autism Speaks-CDC workshop on evaluating changes in the prevalence of autism. Now that the CDC has published the meeting summary, I’d like to offer a few thoughts on the discussions and findings that came out of this meeting.

I wish I could say we had a solid conclusive finding, but we didn’t. If anything, we emerged with more questions than we had when we started. That said, the meeting did produce worthwhile results that will help shape plans and directions for the work ahead of us.

At the outset, we agreed that autism diagnoses have become far more common in recent years. However, we could not decide how much of the increase is an artifact of greater awareness and evaluation as opposed to a true change in incidence. It’s possible both things are happening. It may be that we are becoming more aware of autism at the same time as it is becoming more common. Or not.

We talked about studies that found “pockets of autism” in particular places and demographic groups. For example, we discussed a study that found autism was more common near interstate highways in California. Does this suggest that traffic is contributing to an overall increase in autism?  We don’t know, because it’s unclear whether this situation is new or long standing.

Even when a situation of high prevalence is obviously new – the “Geek enclaves” around tech companies being a good example – we don’t know if this is contributing to an overall increase, or simply concentrating autistic people from a wide area into a single spot.

We also lack clear understanding about recognized differences in autism prevalence among different ethnic groups and nations. I don’t think we will fully answer questions like this until we have a definitive medical test for autism and put cultural and national differences in evaluation and diagnosis to rest.

Over the last decade we’ve discovered a number of genetic mutations and a few environmental factors that are implicated in autism. The trouble is, none of these things are new to the world, either. Take mercury as an example. Mercury has been around longer than humanity. People have handled and even eaten the stuff as long as we’ve had industry. Have you ever heard the phrase, “mad as a hatter?” It refers to people in the hat-making trade, who suffered mercury poisoning 200 years ago.

By way of context, we discussed the broad and alarming rise in childhood allergies and sensitivities. Two well-known examples are asthma and peanut allergy. Fifty years ago the former condition was rare among schoolchildren and the latter was almost nonexistent. Today, both are commonplace.

Many researchers in many fields are trying to understand the increase in these conditions. Could some common factors be contributing to all of these “epidemics,” including autism?  It’s certainly possible.

One excellent question is this:  Are we more susceptible to immune disorders in general now, and if so, why?  An autism causation-immune disorder connection, combined with a generally greater sensitivity in children today could be a scary prospect.  Is it real?  We don't know, and we're working hard to find out.  

Some laypeople blame it all on “Western diet and lifestyle,” but that is not specific enough for us to take real action. There are many questions to explore, but answering them will take years of additional study, and the answers may simply lead to more questions.

For example: Is the proliferation of genetically engineered food affecting us in unexpected ways? Is factory farming harming us by largely eliminating the diversity in our food supply (genetic and otherwise)? Is our shift away from outdoor activity in favor of sedentary activity impacting conditions like autism?

These are all good questions. I wish I knew the answers. I will say this: I do my best to eat a wide variety of organic foods, walk and engage in physical activity as my ancestors did. I don’t need a study to show the personal benefits of that lifestyle change.

Unfortunately, none of that helps us understand today’s rise in autism diagnoses. The essential problem is this: Since we don’t know what causes most autism, it’s difficult to make sense of prevalence findings.

Just consider the thought process when we find a town with a high incidence of autism. Is it because the doctors are particularly observant there? Is it because there is a chemical plant nearby?  Is it because there is a science company there, and they employ a lot of people on the spectrum who produce autistic offspring in greater than average numbers?

All are possible explanations, but the history of science and discovery tells us the true explanation may well be something none of us imagined. Yet.

If there was one thing we agreed on at this workshop, it was the broad scope of what we do not know. One outcome of this workshop was a “punch list” of things we should be doing to move our understanding forward in meaningful ways. Without additional knowledge, we can speculate, but guesses aren’t answers, as much as we want them to be.

Another central issue is this: In the absence of a hard test for autism, we must rely on observation and discussion to diagnose it. That makes our diagnoses “softer” than we’d like. A person who was diagnosed with mental retardation in one decade might well have been diagnosed autistic the next. Even more confusingly, he could end up with both diagnoses, which really confounds our efforts to evaluate prevalence.

Many people who receive Asperger diagnoses today would not have received any diagnosis thirty years ago. I know because I am one of these people. Is there any evidence that the population of Asperger people is really growing?  I didn’t see any, but neither did I see any evidence that it’s not. All the numbers are going up.

Some of the questions we study sound funny, but I know them to be serious. For example, one study asked, “Is autism diagnosis contagious?” In fact, the likelihood of a child being diagnosed with autism is much higher if he’s in a community that contains other autistic kids. No one is suggesting people “catch” autism from the kids around them, but parents and professionals may well “catch awareness” from the first autistic kid they encounter.

Factors like that, and today’s broad public awareness of autism, certainly contribute to the rise in diagnoses.

For many years, we have recognized that one to two percent of the human population has significant developmental disability, such as severe autism or intellectual disability. A much larger percentage of the population has less severe developmental disorders, which include Asperger syndrome, attention deficit and hyperactivity disorder (ADHD) and learning disability. The total affected by these less severe differences is quite large – at least ten percent of the population according to studies of school-age children.

That’s a big umbrella, enough to contain the whole autistic population and then some. Is the umbrella growing, or is autism just taking a bigger share?  I wish I knew.