From age one, Hank Kovach suffered from severe epilepsy that could not be controlled with medicine. His mother, Megan, says he could have more than 25 seizures a day.

"One time, I thought he was playing in the other room," she told CBS News. "He was not playing in the other room, he was convulsing, turning blue. And that's when I thought I lost him."

Twice a day, Hank Kovach receives a marijuana liquid extract called Epidiolex as part of a small trial designed to see if medical marijuana could help with his severe epilepsy.

Last summer, she eagerly enrolled her son in a small trial designed to see if medical marijuana could help.

Twice a day, Hank receives a marijuana liquid extract called Epidiolex. The medicine does not contain THC, the ingredient that can cause euphoria, anxiety and paranoia. Kovach said the change in her son has been dramatic.

"We instantly saw results," she said. "He was smiling again. We saw a decrease in seizures. At this point, he was finally able to gain cognitive skills with therapy."

One-hundred thirty-seven children and young adults, average age 11, were given the drug. After 12 weeks, parents reported the number of seizures declined 45 to 50 percent.

"They had better sleep, better attention, better cognitive concentration, better behavior. Some of the kids clearly became more verbal, better coordination," said Dr. Linda Laux of Lurie Children's Hospital in Chicago, one of the researchers.

"I had one child who started walking while they were using the medication."

Now age 7, Hank still cannot speak, but is able to attend school, and has not had a seizure in months.

"My hope is for him to be seizure free, be happy," Kovach said. "My goal is to hear his voice, to hear him talk. We just want him to be happy."