A growing number of clinical trials are looking into whether compounds in marijuana can be used to treat some of the symptoms of autism.

One of these clinical trials was just announced at the University of California, San Diego, and others are slated to take place in New York at Montefiore Medical Center and New York University, and in Israel at Shaare Zedek Medical Center.

These trials were prompted, in part, by the success of other clinical trials investigating whether cannabis could effectively and safely treat other neurological disorders, including two rare forms of epilepsy and a condition called fragile X syndrome. [7 Ways Marijuana May Affect the Brain]

There have also been a slew of anecdotal stories from parents of children with autism saying that cannabis improved their children's symptoms. But more evidence is needed to make sure that specific compounds in cannabis are a safe and effective treatment for symptoms of autism spectrum disorder, said Dr. Orrin Devinsky, director of NYU Langone's Comprehensive Epilepsy Center, who is involved in two of the upcoming clinical trials. (Parents should not give their children cannabis, or cannabis-related compounds, without consulting with a doctor first.)

"There's not been a huge amount of data generated in this area," Devinsky told Live Science. "There's a lot of religion and not a lot of science."

New clinical trials

Autism spectrum disorder — a neurodevelopmental condition that affects communication, behavior and the ability to interact with others — is diagnosed in an estimated 1 in 59 children in the U.S., according to the Centers for Disease Control and Prevention.

There is no cure for autism (although a small percentage of children do appear to outgrow it), and there are few treatments for its symptoms. But, because of the potential promise of cannabis treatments, the Ray and Tye Noorda Foundation, a nonprofit based in Utah, donated $4.7 million to the Center for Medicinal Cannabis Research (CMCR) at the UC San Diego School of Medicine — the largest private gift to date for medicinal cannabis research in the United States, according to an April 25 statement from the university.

Researchers at the CMCR plan to use the money to run a clinical trial testing whether cannabidiol (CBD), a nonpsychoactive compound in cannabis, can improve symptoms in children with severe autism, they said in the statement. (Unlike tetrahydrocannabinol, or THC, the psychoactive compound in marijuana, CBD does not cause a "high.")

The goals of the trial include determining whether CBD is safe, tolerable and effective in children with autism; whether and how CBD alters chemical messengers, known as neurotransmitters; if it improves brain connectivity; and whether biomarkers of brain inflammation, also associated with autism, are altered by CBD, the researchers said on the CMCR website.

The double-blind, placebo-controlled study, which is set to start a year from now, will be small — just 30 children ages 8 to 12. (A double-blind, placebo-controlled study means that half of the participants will be given a placebo instead of the drug, and neither the researchers nor the participants will know who received which compound until the trial is complete.)

Meanwhile, researchers are planning to test cannabidivarin (CBDV), another nonpsychoactive compound in cannabis, in a double-blind, randomized and placebo-controlled clinical trial of 100 children with autism, according to ClinicalTrials.gov. The goal of the trial is to see whether CBDV can improve certain behaviors of children with autism, said Devinsky, who is working on the trial with Dr. Eric Hollander, a clinical psychiatrist at Montefiore Medical Center.

Devinsky is working on another clinical trial at NYU, which will also investigate whether CBD is a safe and effective treatment for children with autism, he said. [11 Surprising Facts About Placebos]

And in Israel, researchers are studying whether a mix of CBD and THC is safe, tolerable and effective in children with autism, according to ClinicalTrials.gov.

That double-blind, randomized and placebo-controlled study will include 150 people ages 5 to 21, and will test participants on several behavioral and social measures over a period of 12 weeks.

Big picture

It's no surprise that more clinical trials are investigating whether different cannabis compounds can be used to treat autism, Devinsky said.

"There's an enormous amount of [cannabis] usage because 29 states and [the] District of Columbia have approved medical marijuana," Devinsky said. "In many of those states, parents of children with autism are able to obtain medical marijuana from a physician and use it to treat a variety of different problems, from anxiety, to aggressive behavior, to sleep problems."

However, he emphasized that it's still unclear whether cannabis can effectively treat these problems without causing significant side effects.

"Hopefully, it will be found to be effective, and hopefully, it will be found to be very safe for these individuals," Devinsky said. "But right now, we just don't have that knowledge."

Original article on Live Science.