It was a horse named Betsy, after all, that Isaacson credits with helping to heal his son Rowan, who was diagnosed with autism just after his second birthday in 2004. The toddler's uncommunicative, tantrum-ridden state devastated his concerned parents.
"Rowan would have as many as 12 tantrums a day," Isaacson, 42, told ABCNews.com. "Everyone knows what a regular toddler tantrum is, but add a deep distress where the child is just inconsolable and unable to communicate the pain that they're in."
"All you can do is try to hold them and stop them from hurting themselves," Isaacson said of he and his wife Kristin's consistent attempts to soothe their son. "When you see your child suffering like that it tears you to pieces."
Isaacson said that he quickly learned that Rowan, who is now 7 years old, would calm down if he was allowed to roam and explore the woods outside the family's home in Elgin, Texas, just outside of Austin.
"One day Rowan went where I wasn't expecting him to go and before I could grab him he was in my neighbor's pasture, right next to a group of horses that happened to be grazing right there," remembers Isaacson. "Rowan dived right under the horse -- every parent's worst nightmare."
While Isaacson said he expected his small son to be trampled by the horse, what came next was life-changing.
"The old boss mare -- who we'd later learn was named Betsy -- walked over and pushed the other horses off," said Isaacson. "Betsy dropped her head and started making a chewing sound that horse lovers know as a sign of acceptance."
"I've never seen a horse offer that to a babbling two-and-a-half-year-old," he said. "Rowan and Betsy obviously had some sort of connection."
It was that connection that Isaacson would later discover held the key to his son's happiness. Isaacson, a horse trainer for most of his adult life, began horseback riding with Rowan, finding that the rocking rhythm of the animal's stride soothed his son. Throughout his horseback riding, Rowan continued with more orthodox therapies, including applied behavioral analysis, one of the most commonly used therapies for kids with autism.
"Whenever he was on a horse he wouldn't tantrum," said Isaacson. "When I put him on Betsy that would be the only time his tantrums would stop, any other situation and he could turn at any point. We wanted to keep him on a horse as long as possible."
In the summer of 2007 when the boy was 5, Isaacson and his family went on a horseback trip in Mongolia, spending four weeks where Rowan was happiest: on the back of a horse.
"Before we went to Mongolia, Rowan was incontinent and subject to neurological fits and tantrums and was cut off from his peers," said Isaacson. "We came back with a child that was toilet trained and no longer having tantrums. He made his first friend on that trip, too."
"It was the most extraordinary thing," he said.
"Rowan is not cured of autism, but healing is a different thing," said Isaacson, who has chronicled his son's adventure in a book titled "The Horse Boy" and a 2009 film called "Over the Hills and Far Away." "He was healed of these three terrible dysfunctions that were impairing his and our quality of life."
"He came back and was still autistic but his autism had quieted down and now it comes out more as a charming quirk," he said. "Now he is conversational, he's in school."
Isaacson said that Rowan attends a home school for kids with special needs, rides horses every afternoon and still participates in more traditional therapy.
But Dr. Paul Offit, a professor of pediatrics at the University of Pennsylvania and the author of "Autism's False Prophets: Bad Science, Risky Medicine, and the Search for a Cure," said he has some concern that other parents may become too hopeful after hearing about Isaacson's experience.
"For disorders like autism, where there isn't a clear cause or cure, I think there is a very strong desire by parents to want to do something," said Offit. "And I think this book fills that need."
According to The Centers for Disease Control and Prevention, in 2007 one in every 150 8-year-olds had an autism spectrum disorder.
"The problem is that I think false hope is a bad thing because one can get exhausted or divert resources that could go to methods that will have empirical evidence that it works, like behavioral therapy," said Offit.
The Autism Society of America has already come out and said they hope to see more research on equine therapy.
Offit said he would advise parents to have a "healthy degree of skepticism" on the therapy.
For example, Offit reminds that it's proven that children with autism tend to be at their worst between ages 2 and 5 and tend to improve between ages 5 and 10, which is when Rowan took his trip to Mongolia.
The Autism Society of America, which openly supports and promotes "The Horse Boy," reports seeing an uptick in the number of parents looking into equine therapy in recent years, even despite the lack of scientific research into its effectiveness.
"We're very hopeful that families who read this story will learn about sensory therapy and seek their own adventures," said Marguerite Kirst Colston, the vice president of constituent relations at the Autism Society of America.
"It's becoming more and more popular, so it must work to some extent," said Colston. "In the past two years we've seen more and more equine therapy programs popping up across the country."
"Children with any medical condition that has sensory issues like autism does relate with animals because animals, by nature, are sensitive," said Colston. "I think that as long as families are seeing something that is benefiting their child, then this sort of therapy is good."
"Is it causation or correlation I don't know, but the point is that the child is happier and getting better," she said.
Dr. Katherine Loveland, the director of the Center of Human development Research at the University of Texas Medical School in Houston, said that she believes equine therapy to be a good supplement to tradition therapies for autism.
"[Equine therapy] is not a primary treatment for autism but it could be a useful adjunct treatment for kids," said Loveland. "There is a lot of anecdotal evidence that it can have a number of positive effects."
Loveland said often times horses are a valuable tool to getting a child with autism to calm down enough to even be able to process new information.
Other animals, said Loveland, are also sometimes used to aid in therapy for children with special needs. Dogs, cats and even dolphins have been widely reported to aid in improving the quality of life for kids with autism.
"The horse is moving and has a rhythm and is warm and so it often acts as a calming experience for kids," said Loveland. "Some kids with autisms have a lot of difficultly with new things or changes and so often a therapist will use the horse to introduce some of those things."
One of the challenges many children with autism face is the inability to interact socially with other people, an obstacle a relationship with an animal may help overcome, according to Loveland.
"Animals are a lower pressure environment for kids to practice certain types of social skills," she said. "Therapists use the horse as a social object for the child to relate to and to read the signals of the horse."
"No, it's not a cure for autism but it may help a child learn some self-regulation and help them to better accept certain times of stimulation from the environment, resulting in a calmer and less agitated child and hopefully a happier family," said Loveland.
And for the Isaacson's, life is far happier today than it was before Rowan began riding.
Isaacson and his wife founded The New Trails Center that offers homeschooling and equine therapy for kids like Rowan, and the family continues to plan upcoming riding trips for their family.
"Every parent of an autistic child knows they have to go up a few blind alleys before they find what will work for their child," said Isaacson. "No one should be so hamstrung by skepticism that it forces them into an extreme position that they stop following possibilities."
"Rowan was healed of some of the dysfunctions he had and that, for us, was miraculous," he said.
"That made the difference between a horrible life and a life where Rowan's life and ours were in harmony."