[Source: Wikipedia]
[Source: Wikipedia]
In 2002 the Center for Disease Control estimated that autism affected about 1 in 150 children. By 2012 the CDC estimate had increased to 1 in 88. Now, according to the latest revision of the estimate recently released, autism affects 1 in 50 children. That's a phenomenal 300 percent increase in 11 years. But do the numbers reflect a real increase in the incidence of autism or are previously undiagnosed cases now being diagnosed? The authors of the study tend to think it's the latter, but others question whether the increase can be explained entirely by wider diagnoses.

In recent decades there has been a consistent increase in the reported prevalence of autism. Two National Health Interview Surveys, national telephone surveys conducted by the CDC, showed prevalence to increase almost four-fold between a 1997 – 1999 survey and a 2006 – 2008 survey. Concurrently, the CDC’s Autism and Developmental Disabilities Monitoring Network showed a 78 percent increase in autism spectrum disorder (ASD), that includes all variants of disease related to autism, between 2002 and 2008.

A new National Interview Survey shows that, between 2007 and 2011 – 2012, the prevalence of parent-reported autistic children between 6- to 17-years-old increased from 1.16 percent in 2007 to 2 percent – or, from 1 in 88 to 1 in 50. But rather than a true increase in the actual prevalence of autism, the authors argue that “...much of the recent increase was the result of diagnoses of children with previously unrecognized ASD.” Consistent with that idea is that the ratio of cases occurring in boys and girls has not changed – boys remain about four times as likely to be affected by autism than girls.

The increase in autistic cases over the past decade is thought to be due to more thorough screening rather than a true spike in autism. [Source: CDC]
The increase in autistic cases over the past decade is thought to be due to more thorough screening rather than a true spike in autism. [Source: CDC]
Reasons for improved diagnoses are speculative at this point, but the authors suggest that greater awareness on the part of the parents and health care professionals could be a factor. They also mention that increased access to diagnostic services, changes in screening practices, or greater access to special education programs might have contributed.

Right now the official government estimate remains at 1 in 88, but additional data suggest that the true incidence of autism is indeed closer to 1 in 50. The 1 in 88 figure is based on school and medical records, so it misses many children not enrolled in assistance programs. Estimates from a survey conducted by Autism Speaks that screened children directly in communities were closer to the 1 in 50 figure. One survey, for instance, that they conducted in South Korea showed 1 in 38 children were autistic.

Commenting on the 2012 study, however, former president of Autism Speaks, Mark Roithmayr, wasn't ready to chalk up the entire increase to a widening diagnostic net. "Only part of the increase can be explained by better and broader diagnoses," he told Time. "There is a great unknown. Something is going on here, and we don’t know."

The symptoms for autism can usually be identified by 18 months of age. Ideally, diagnosing autism would involve comprehensive behavioral evaluations, which can be complex and time-consuming. But new data suggests that brain scans may be effective in diagnosing autism, even in children as young as six months. While that technology matures, however, clinicians and parents are left with traditional methods. And although the American Academy of Pediatrics recommends that all children be screened by age two, many of those with milder symptoms don’t actually get diagnosed until they are old enough to attend school where difficulties with peer interactions gain the attention of teachers and parents.

Scientists continue to struggle to determine the root cause of autism. It is a complex condition, as indicated by the broader term, autism spectrum disorder, but it’s thought to be about strongly related to genetics. The CDC plans on following up the current study by taking a more detailed look at its findings and analyzing correlations between autism prevalence and sociodemographic factors and differences in healthcare. That won’t get to the genetic root of the disorder but may uncover environmental factors that contribute to its cause.

As slow as the going may be, progress is being made in the diagnosis and prevention of ASD. In addition to the new brain scan studies, one recent study suggests that taking folic acid during pregnancy may actually decrease chances for ASD. The possibility that more children with autism are being detected will not only benefit the children but, in the long run, hopefully researchers as well.

Peter Murray was born in Boston in 1973. He earned a PhD in neuroscience at the University of Maryland, Baltimore studying gene expression in the neocortex. Following his dissertation work he spent three years as a post-doctoral fellow at the same university studying brain mechanisms of pain and motor control. He completed a collection of short stories in 2010 and has been writing for Singularity Hub since March 2011.