Lori McIlwan's son Connor was 7 years old when he walked away from the playground of his public elementary school and started toward a busy, four-lane highway. It was not the first time Connor, who has autism, is non-verbal and fascinated with highway exit signs, had wandered off. But it was the most serious.

Eventually, a driver recognized that Connor was too young to be walking by himself and pulled over.

"He put my son in the car, because [Connor] was not answering any of his questions," McIlwan told The Huffington Post. "He began driving around with him, not knowing where he belonged." The man stopped by a local school to see if they could identify the boy, but it wasn't the right one. Eventually, the police were called. They thought Connor was being silent because he was defiant, not recognizing that he has autism.

"By the time I got to him, he was hysterical," McIlwan recalled.

Half of parents whose children have an autism spectrum disorder (ASD) say their kids have wandered off at least once. Of those, half have gone missing long enough to cause serious concern, according to the first major study to quantify autism-related wandering, or "elopement."

Of those who have gone missing, nearly 25 percent were in danger of drowning and 65 percent were in danger of a traffic-related injury, according to the findings published Monday in the journal Pediatrics.

"This is one of the most important issues with autism, and it has not been addressed much at all prior to this study," said Dr. Paul Law, author of the study and director of medical informatics at the Kennedy Krieger Institute.

"The bad news is, it is very common and probably the problem that puts children [with ASD] at greatest risk for an early death," he added.

Using an online questionnaire, Law and his colleagues collected information from the families of more than 1,200 parents of children with ASD -- and more than 1,000 siblings without -- about their children's tendency to wander away from safe spaces. The families were registered with the Interactive Autism Network, a large-scale effort to connect individuals affected by autism with researchers. Just under half of the children with ASD had autism, while 20 percent had an Asperger disorder and the remaining children had some other developmental disorder.

Children who wandered were most likely to run away from their own homes or someone else's, but they also left stores and classrooms or schools. Runaway attempts peaked at five-and-a-half years old.

When asked to describe the worst year they'd had in terms of wandering incidents, 30 percent of parents said their child had attempted to run away multiple times daily, while 35 percent said it happened at least once a week.

The researchers also found that children with more severe cases of autism were more likely to run away.

"What this study does is highlight an important topic. It doesn't go into depth about all of the reasons why it happens," said Dr. Roberto Tuchman, director of the autism and neurodevelopment program at Miami Children's Hospital's Dan Marino Center. "What it does say is that elopement is a very big and very serious issue."

The most common motivation for elopement, parents said, was that their child "simply enjoys running or exploring." Other explanations were that the child wanted to reach a place he or she enjoys, or was attempting to escape an anxious situation or uncomfortable sensory stimuli. Other children wanted to pursue his or her "special topic," parents reported.

"It's not just wandering," Law said. "There's bolting. There's seeking. There's running and fleeing."

But all of these behaviors, he stressed, are rooted in the core symptoms of ASD -- a group of developmental brain disorders characterized by difficulties in social interaction and communication, as well as repetitive behavior.

"The majority, if not all of the behaviors that occur with children with ASD have a basis in communication," Tuchman said. "Elopement is a breakdown in communication, as with many other behaviors associated with autism."

The new study also highlights how difficult wandering is for parents of children with ASD: More than half of respondents said it was one of the most stressful behaviors they had to cope with, and half indicated they'd received no guidance on how to prevent or cope with it.

"A lot of times the response is, 'This is happening because of bad parenting,'" said McIlwan, who is also executive director of the National Autism Association. "But it's happening in all settings, with all different types of supervision. I think this idea that it's a 'bad parenting' issue makes it difficult to get the support they need."

McIlwan said that Connor, her son, now wears a tracking device. She and her husband have also installed stop signs on the doors in their house and a high-pitched chime alerts them when any door is opened. McIlwan has also worked with her son's school to make sure he's supervised at all times, particularly when walking between classes or when on the playground.

With the Centers for Disease Control now estimating that 1 in 88 children in the U.S. has been diagnosed with ASD, experts say there is a pressing need for devising clear best practices for managing "elopement." Parents and health care providers must be aware of the potential risks, but so too must first responders and people in the community, Law said.

"On the broadest scale, it means we as a nation need to get a system organized so that when children do elope, and when parents call to report it, there's an immediate response," he said. "The likelihood of them having a very bad outcome is dramatically increased the longer it takes to recover a child in a safe place."

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