News and Knowledge

The following article was posted to Children’s Hospital Boston’s health and science blog on November 3rd, 2009 by Ellen Hanson, PhD, of the hospital’s Developmental Medicine Center.

“Has autism increased or hasn’t it?” As a researcher and psychologist with a specialty in developmental disabilities and autism spectrum disorders (ASDs), this is a question I get all the time. I wish I had a short answer, but I don’t. On the other hand, if you have a few minutes, read on.

The question is a really important one. A study just came out in Pediatrics, saying that the prevalence of ASDs is now one in 91 U.S. children – and one in 58 boys. This is much higher than the most recently quoted rate of one in 150. And that is up from one in 1500 in the early 1990s.

That jump would scare anyone! But is it real?

This should be a “yes” or “no” question, right? But the first thing to remember is that, although we do our best, it can be really difficult for researchers to get good autism numbers. Previous studies looking at this issue have used differing criteria for deciding who has an ASD. Some studies try to use particular criteria to “make sure” that the individual has an ASD and not some other disorder – for example, requiring that the diagnosis come from a specialist, or that the patient displays certain symptoms. In contrast, the study in Pediatrics used parent or guardian reports and got a much higher rate of diagnosis. This isn’t necessarily because the parents were inaccurate, but rather that they could report a diagnosis or an observation made by any provider using any set of rules or criteria.

Another issue is that reporting of disorders can rise for reasons other than a true increase. For example, when there are treatments that work and are available, people are more likely to pursue getting a diagnosis. In the case of ASDs, when laws were enacted to ensure that young children had more access to services, there was an increase in diagnosis

Yet another factor is increased public awareness. When you know that you have risk factors for a disorder, you are more likely to be evaluated. And as awareness increases, people tend to get diagnosed much earlier, adding to the pool of people who have the diagnosis at any given time.

After all this, you’re probably still saying, “So, do we know if ASDs have increased at all?” And truthfully, we just don’t have a definitive answer. Certainly there is an increase in prevalence, or the number of people diagnosed with an ASD at any given time. The incidence of ASDs, or the number of new cases over a certain time span, is less clear. But even when the reporting issues above are taken into account, new cases do appear to be increasing.

Why this is so remains a big mystery. Children’s is one of the institutions trying to find answers – using very stringent, rigorous methods for diagnosing autism and analyzing the data so we can look for causes, improved diagnostic techniques, better treatments and ultimately cures. If you have a child with autism, we need your help! Consider enrolling in our study, which looks at the genetics of autism, or other studies taking place at the hospital (for more information, email Anna Ehler or call 617-355-3076). You’ll get a report on your child and you’ll be helping researchers make new discoveries. Whether it’s one in 150 or one in 91, ASDs are a huge public health problem, and we need answers quickly.