Mykayla Comstock, 7, Treated With Medical Marijuana for Leukemia; Parents At Odds Over Drug

Twice a day, Mykayla Comstock takes a pill filled with cannabis oil, medical marijuana. The 7-year-old has an aggressive form of childhood leukemia.

Her mother, Erin Purchase, is a firm believer in the healing powers of cannabis, and signed Mykayla up for doses of medical marijuana, which is legal in their home state of Oregon, just three days after the girl was diagnosed with cancer.

"The first doctor was not for it at all," Purchase told ABC News. "She was rude and she told us it was inappropriate. "Basically she blew up at us and told us to transfer to another facility."

They did, and Mykayla's new doctor is aware of her drug regimen, though the family hasn't discussed it explicitly.

Mykayla is undergoing chemotherapy treatment for leukemia, which can cause loss of appetite, nausea and insomnia. "It helps me eat and sleep," she said. "The chemotherapy makes you feel like you want to stay up all night long."

"First you get hungry," she said. "Then you get really funny, and then you get tired."

Each pill contains about half a gram of cannabis oil, equivalent to the THC present in four or five joints.

Mykayla was diagnosed with leukemia in July. Her form of the disease is especially aggressive, and doctors surmised that she would need a bone marrow transplant.

She started taking the cannabis pills in early August, and her cancer soon went into remission. Her mother praises the marijuana.

"I don't think it's just a coincidence," Purchase said. "I credit it with helping -- at least helping -- her ridding the cancer from her body."

Mykayla's father disagrees. Jesse Comstock is divorced from Purchase, and works on an oil field in Nebraska. He visited his daughter in August. "She was stoned out of her mind," said Comstock. "All she wanted to do was lay on the bed and play video games."

There are 51 other children currently using medical marijuana under Oregon's program. Four of them are between the ages of 4 and 9, so Mykayla is not the only child her age using the drug, nor the youngest.