When Noa Shulman came home from school, her mother, Yael, sat her down to eat, then spoon-fed her mashed sweet potatoes — mixed with cannabis oil.

Noa, who has a severe form of autism, started to bite her own arm. “No sweetie,” Yael gently told her 17-year-old daughter. “Here, have another bite of this.”

Noa is part of the first clinical trial in the world to test the benefits of medicinal marijuana for young people with autism, a potential breakthrough that would offer relief for millions of afflicted children — and their anguished parents.

There is anecdotal evidence that marijuana’s main non-psychoactive compound — cannabidiol or CBD — helps children in ways no other medication has. Now this first-of-its-kind scientific study is trying to determine if the link is real.

Israel is a pioneer in this type of research. It permitted the use of medical marijuana in 1992, one of the first countries to do so. It's also one of just three countries with a government-sponsored medical cannabis program, along with Canada and the Netherlands.

Conducting cannabis research is also less expensive here and easier under Israeli laws, particularly compared to the United States, which has many more legal restrictions.

Autism is one of the fastest-growing developmental disorders, affecting 1 in 68 children in the United States, according to the Centers for Disease Control and Prevention. Its debilitating symptoms include impaired communication and social skills, along with compulsive and repetitive behaviors. Autism typically emerges in infancy or early childhood.

Advocates for combating the disorder are calling attention to it by declaring April National Autism Awareness Month.

Noa's mother has to feed and bathe her and change her diapers. Noa is unable to speak and often behaves aggressively. Yael, a mother of three with a full-time job in this city halfway between Jerusalem and Tel Aviv, has tried to find caretakers to help, but they don’t last long.

Only two medications have been approved in the United States by the Food and Drug Administration to treat the symptoms of autism. Both are antipsychotic drugs that are not always effective and carry serious side effects.

When Noa took them, “she was like a zombie,” Yael said. “She would just sit there with her mouth wide open, not moving.”

Noa is part of a study that began in January at the Shaare Zedek Medical Center in Jerusalem. It involves 120 children and young adults, ages 5 to 29, who have mild to severe autism, and it will last through the end of 2018.

Adi Aran, the pediatric neurologist leading the study, said nearly all the participants previously took antipsychotics and nearly half responded negatively. Yael desperately pushed Aran and other doctors to prescribe cannabis oil after a news report aired about a mother who illegally obtained it for her autistic son and said it was the only thing that helped him.

“Many parents were asking for cannabis for their kids,” Aran said. “First I said, 'No, there’s no data to support cannabis for autism, so we can’t give it to you.'”

He said that changed about a year ago after studies in Israel showed that cannabis helped children with epilepsy by drastically reducing seizures and improving behavior for those who also have autism. Epilepsy afflicts about 30% of autistic children, Aran said.

Mounting anecdotal reports of autistic children who benefited from cannabis also led Aran to pursue more scientific testing. After seeing positive results in 70 of his autistic patients in an observational study, Aran said, “OK we need to do a clinical trial so there will be data."

Study participants are given liquid drops like those mixed into Noa's sweet potatoes. They receive one of two different cannabis oil formulas, or a placebo. The oil does not cause a high because of low levels of THC, marijuana's main psychoactive ingredient.

Yael doesn't know if her daughter is receiving the cannabis or a placebo. Noa is calmer on some days since beginning the trial, she said, but on other days she's aggressive and irritable.

Even so, just being a part of the study gives Yael hope. “I had really come to a point where I no longer had the power — not physically, not emotionally,” she said.

More than 110 cannabis clinical trials are underway in Israel — more than any other country, according to Michael Dor, senior medical adviser at the Health Ministry’s medical cannabis unit.

Alan Shackelford, a Harvard-trained physician, sparked a surge in American interest in cannabis treatment for epileptic children in 2013, when he used medical marijuana to treat a young girl in Colorado and her seizures drastically decreased. He said he tried for years to conduct clinical trials in the U.S., but “I was meeting nothing but closed doors to study something that was so clearly beneficial.”

Shackelford said a colleague spent seven years trying to get approval from U.S. authorities to study cannabis treatment for post-traumatic stress disorder. By contrast, Aran said it took Israel’s Ministry of Health six months to approve his clinical trial with autistic children.

“Israel leads the world in inquiries and studies on cannabis as a potential medical treatment,” said Shackelford, who recently launched an Israeli company to conduct research on medical cannabis here because of the restrictions he faced in the United States.

He said the U.S. government has funded $1.4 billion in marijuana research since 2008, but $1.1 billion of that went to studying addiction, withdrawal and drug abuse.

Aran cautioned against premature conclusions about cannabis as a treatment for autism, but he said many children have shown significant improvements. Some no longer hurt themselves or throw tantrums. Some are more communicative. Others were able to return to classes after they had been suspended for behavioral problems.

Tamir Gedo, CEO of Breath of Life Pharma, which provides the cannabis oil for the study, said one mother reported, "My child is speaking relentlessly. … He never spoke before. And he's 12 years old.”

One major concern is the long-term impact of prescribing cannabis to young patients, said Sarah Spence, co-director of the Autism Spectrum Center at Boston Children’s Hospital. “There certainly could be harm” to brain development, she said.

But opioids and antipsychotic drugs currently prescribed to children are more harmful, said Gedo. “These families have no other hope.”