"It's more likely that genetics coupled with environment stressors may be just one combination that suggests cause," Shulman said.
Shulman said finding a cause will allow for individualizing treatments. So far, applied behavior analysis -- an early educational intervention that teaches social, communication and behavioral skills -- is the primary scientifically based treatment recommended by medical professionals.
But there are also alternative medical and educational interventions available to families that are not scientifically proven to be effective. Some believe that these methods offer positive results and, in lieu of evidence-based treatments, may be the best bet.
But Shulman noted that although evidence-based treatments are scarce and time may be of the essence when it comes to treatment, parents should be wary of treatments that are not scientifically supported.
"If you choose to experiment on your child, and not wait for appropriate scientific evidence to catch up, then recognize that you're in fact only experimenting with your child and that you are taking that risk," Shulman said.
For parents like Senator who have passed the stages of diagnosis and early intervention, the concern for their children may not revolve around medical treatments, but rather having their child learn independent living skills.
Under the Individuals with Disabilities Education Act, a federal law that guarantees public education for developmentally disabled children, a child with autism is mandated to receive schooling through age 21. After an autistic child becomes an adult, there is no longer a federal directive to provide services for individuals on the autism spectrum.
Some options for adults with autism may include group homes for developmental disabilities and day programs to teach societal integration. But many programs do not cater specifically to autistic individuals, whose symptoms differ from many other developmental disabilities. Recently, many states have increased the number of educational services in order to accommodate the number of individuals diagnosed on the autism spectrum.
Senator envisions adequate support services that will improve her son's quality of life. Senator hopes that he will learn basic living skills so that he can one day live on his own.
"When we're gone, we want to make sure to the greatest degree possible that Nat can depend on less people," Senator said. "That, I think, is the biggest fear many families have."
Geshwind said the state of support services cannot completely dispel these fears. But advancements in care may one day alleviate many of these concerns.
"If you look at the prognostic studies done now showing what the trajectory of autism is, only 25 percent of children at all levels become independent as adults," Geshwind said. "The goal of our research is to make that extra 75 percent independent, as well."
Senator said she is uncertain of her son's future beyond the next three years in his residential program. But, she said, he has continued to be involved in his community by participating in Special Olympics. Nat also recently began working at a chain pizza store.
"We want to see people like Nat working if possible [and] continuing their education," Senator said. "The ideal for me is to see Nat participate in the world through the greatest degree possible."