Jayden is not just walking, he's running. He plays at a park, climbing up and down the steps of the jungle gym. He swims at his local pool, splashing in the water with his father and other children. He loves to go to Fuddruckers to dig into his favorite food, a cheeseburger with mushrooms. His father has begun to wean him off the powerful pharmaceutical pills, which he believes have kept his son from developing properly.

The liquid, nonpsychoactive form of marijuana that Jayden takes ensures the boy doesn't get "high." In a laboratory, the marijuana is distilled down to mostly cannabidiols, which advocates say is the potent medicinal value of the drug.

Harborside Health Center, a medical marijuana clinic in Oakland, Calif., helped create the original tincture Jayden took. The center still analyzes and tests the marijuana before David administers it to his son. Harborside says it helps a number of child patients, including Jayden, whose parents legally obtain the marijuana.

"Parents don't want to bring their children to something controversial like cannabis," says Harborside's executive director, Steven DeAngelo. "They do it reluctantly, and they do it because they're at their wit's end."

Eighteen states have legalized marijuana for medicinal uses or limited personal use. California, which has the nation's largest number of registered users, does not keep demographic data on its registrants. But Colorado has 45 registered users under age 18, Oregon reports 56 child users and Montana has 55.

DeAngelo says children with severe autism, epilepsy, ADHD and cancer can be helped by medicinal marijuana. But those sick children, says DeAngelo, often face barriers to accessing marijuana.

"What I worry about are the thousands and thousands of children like Jayden who are suffering unnecessarily, who I know we could help," he says. "The only thing separating them from help are outdated rules that need to be changed."

Those rules are at the federal level, where marijuana remains illegal.

Dr. Seth Ammerman, a pediatrician and specialist in adolescent substance addiction, acknowledges anecdotal reports like Jayden's remarkable turnaround. But he warns that a parent is "flying by the seat of his or her pants" when it comes to treating children with marijuana.

"I do think there's potential for these cannabinoids to be medically relevant, but at this time we don't know the risks," says Ammerman. Because marijuana is illegal at the federal level, the government hasn't conducted any thorough research on the possible medicinal benefits.