A cannabis oil that includes a small amount of the drug that gives pot smokers a high appears to be effective in helping kids with a severe form of epilepsy, a new Canadian study has found.

Researchers at The Hospital for Sick Children have conducted a small study on an experimental oil using 20 children with a form of epilepsy that is notoriously hard to treat, called Dravet Syndrome.

The rare form of epilepsy begins in the first year of life and causes prolonged and frequent seizures. Some children have more than 1,000 seizures a month, leading to significant developmental delays and learning disabilities. The condition is incurable and while traditional epilepsy medications can reduce the frequency of the seizures, they often fail to fully control them.

In recent years, there has been growing interest in cannabis oils as a treatment. One large study published last year in the New England Journal of Medicine found that kids with Dravet Syndrome who were given a cannabis oil along with their regular medications saw their monthly seizures cut in half, with some kids even becoming seizure-free.

Last month, the U.S. FDA approved the first cannabis-based medication to treat two forms of epilepsy in patients 2 years and older.

But that medication and the oil used in the NEJM study contain only CBD, or cannabidiol -- the marijuana ingredient that has been the focus of much of the interest in cannabis for epilepsy control.

This new SickKids study tested a cannabis extract oil with both CBD and a small amount of THC, or tetrahydrocannabinol, the marijuana ingredient that produces the euphoric effect pot is known for.

Recent research has suggested that THC-containing cannabis oil might be superior to CBD-only preparations in reducing seizures, but there has been concern about how kids would tolerate such a treatment.

This study found that most of the children saw a significant drop in their seizures after taking the drug for several weeks, with none of their caregivers reporting the kids developed any hallucinatory effects.

The encouraging findings offered a sense of relief for Barry Pogson, whose 5-year-old daughter Kate lived with debilitating seizures that could last up to an hour.

Kate now takes cannabis oil twice a day, and Pogson says she’s almost completely seizure free.

“No more ambulances, no more emergency rooms. It’s amazing. I couldn’t be happier for how well she’s doing,” said Pogson, who lobbied doctors for years to look into the ointment’s medical value.

The study focused on 20 kids with Dravet Syndrome who were an average age of 10. Each was given a product called TIL-TC150, which contains CBD and THC at a ratio of 50:1. It was donated by the oil's manufacturer Tilray, a Canadian cannabis plant extract company that also funded the study.

The study leaders began the children on the product slowly, increasing their dosage slowly over several weeks, though only eight of the patients reached the dose the researchers had set as their target.

For 16-year-old Abigail, who participated in the study and has had Dravet since she was eight months old, the results were astounding.

“Within the first month of the oil, she went from eight to 10 seizures a month to four to five. Over the course of the year, we’re down to less than one every two months,” Abigail’s mother, Laura Weightman, told CTV News.

As Abigail’s seizures decreased, her family has also seen other positive changes, such as her ability to communicate.

“We’ve seen this learning. She’s trying to say new words all the time,” her mother said.

Most of the children developed side effects along the way, including increased sleepiness, decreased appetite and diarrhea. But these effects improved in most as the children developed tolerance to the CBD-THC oil.

"In the participants who reached the target treatment dose we saw a statistically significant reduction in motor seizures, and an increase in seizure-free days compared to those who did not reach the target dose," Dr. Blathnaid McCoy, a neurologist at SickKids who took part in the study, said in a statement.

The higher the dose, the better their seizures were brought under control. And many caregivers reported that the children's quality of life improved significantly.

"We observed promising clinically beneficial effects including a reduction in seizure frequency and improvements in certain aspects of adaptive functioning and quality of life measures," McCoy said.

McCoy says this study adds "to a growing body of evidence that cannabinoids can exert anti-seizure effects and are safe and tolerable in treating pediatric DRE."

She and her team hope their findings will now lead to a larger study of how these oils can help more kids with drug-resistant epilepsy.

The full results appear in the journal, Annals of Clinical and Translational Neurology.

With files from CTV’s medical affairs specialist Avis Favaro and producer Elizabeth St. Philip