A rising number of children’s videos and television channels have created an abundance of viewing opportunities for babies and toddlers over the last 25 years. The American Academy of Pediatrics has since recommended no screen time for children under 2 years old, and these types of media — once touted as educational — have been linked to developmental delays.
Now, one Drexel ophthalmologist hypothesizes that exposure to audiovisual materials during infancy could be a possible contributing cause of Autism Spectrum Disorder (ASD).
Karen Heffler, MD, an associate professor of ophthalmology in the College of Medicine, argues that, for babies who are already genetically predisposed to autism, television and videos may actually re-wire their brains in such a way that they are less likely to respond to social stimuli, like facial expressions.
The theory is outlined in a paper published in the June print edition of Medical Hypotheses. The journal publishes papers that “describe theories, ideas which have a great deal of observational support and some hypotheses where experimental support is yet fragmentary.”
Heffler’s own 24-year-old son is on the autism spectrum, which has led the researcher on a search for answers about the developmental disorder. One in 68 children have been identified with autism, the Centers for Disease Control and Prevention estimates.
Through her participation with several nonprofits and experiences with her son, Heffler realized that many children on the spectrum are fixated on watching certain TV programs, movies and video clips.
But it was her career studying eyes that gave her insight into why this might be.
If an infant is born with a congenital cataract — a clouding of the eye lens — physicians know the baby should be operated on within several weeks or months, Heffler said. If surgery comes later, the cortical neurons in the brain that would process the vision coming from the blocked eye, instead respond only to the functional eye. Once the cataract is removed surgically, the infant’s vision may remain blurred, because the neurons have adapted their signals connect with to the other eye.
This knowledge made Heffler aware that early visual experiences impact brain connectivity. If diminished vision in one eye could have such a profound affect on brain and behavior, then perhaps visual stimuli during infancy could also affect how neural connections are organized in the brain, she thought.
The theory is intriguing, considering that the rise in autism after the 1980s correlates strongly with the time that cable television and VCRs became more common in the home.
Despite this apparent trend, there are only two research studies to date that directly link autism rates and exposure to entertainment media during infancy. In 2006, a group of Cornell University economists published findings from a study that tracked autism incidence in four states. The researchers found that as cable television became more common, childhood autism rose more in counties that had cable than in the counties that did not. Another study showed that earlier TV viewing, as early as 6 months, and more hours of viewing were associated children who received an autism spectrum diagnosis.
More recent studies have indicated that autism cause is likely a combination of both genetic and environmental factors. While Heffler acknowledges that correlation does not necessarily equal causation, she thought the findings from Cornell deserved a closer look.
In her paper, Heffler and her co-author analyzed a number of studies to propose a new model of autism causation. These studies showed not only that many infants are exposed to entertainment media during infancy, but also that children with autism process speech, audio and visual stimuli differently than children without autism.
“It was surprising to me once I looked at the literature and various research studies, that so many seemed to point in this direction,” Heffler said. “Looking at the evidence through a different lens, I was able to develop this hypothesis.”
Television and videos, unlike the real world, offer no reciprocal social rewards, according to Heffler.
“For instance, if a baby smiles or gazes into his mother’s eye, the adult would respond to that. But it a baby laughs at someone on TV, he will not receive a response from the screen,” she said.
While older children and adults have developed the typical brain pathways “that process the world in terms of social relatedness and speech,” the paper says, a newborn would process the sounds and images on TV without any social meaning. These early exposures to pure audiovisual stimuli may drive sensory brain hyper-connectivity, which in turn alters the infant’s behavior and impacts further social and cognitive growth.
“If what they are paying attention to is determined by the pure sensory stimuli, rather than social cues, that is very different than typical development,” Heffler said.
James Connell, PhD, clinical director of the A.J. Drexel Autism Institute who was not affiliated with the paper, points out that while Heffler presents an interesting hypothesis, infants in fact interact with many other “human-like” objects, besides audiovisual materials — such as picture books and dolls.
“It is not clear to me how audiovisual input is different from any of these other two-dimensional inputs,” Connell said. “I think the authors would need to speak to that first.”
Further, he said, it would be nearly impossible to conduct the types of rigorous, retrospective studies needed to prove the claim that TV-watching during infancy and autism are linked. That being said, he is a big proponent of limiting the amount of technology that children and adolescents with autism interact with.
“ASD is a social-communicative disorder. So, despite how the neural pathways were changed, it seems counterproductive to put a child in front of technology who lacks the ability to communicate with his or her peers,” he said. “Teaching those kids how to interact with the world is very important.”