In Michigan, 44 residents younger than 18 have a medical marijuana card, according to the Detroit Free Press.

One 14-year-old uses medical marijuana in an effort to control seizures caused by a rare form of epilepsy. His mother says his seizures have been dramatically reduced since he started using medical marijuana earlier this year. Other children ages 7, 9, 11 and 13 also have the cards. Parents say they have used medical marijuana to treat their children for autism, muscular dystrophy, attention deficit disorder, and pain and nausea caused by cancer.

Children in Michigan must have two doctors approve the use of medical marijuana. Most states that have legalized medical marijuana do not require that users be at least 18. Delaware and Connecticut do have such a requirement, according to the newspaper.

Some critics say there is not enough evidence about marijuana’s effects on developing brains and nervous systems, the article notes. “I don’t think we know in growing nervous systems what effects it might have,” said Dr. Tom George, a practicing physician and former Republic state senator, who voted against legalizing medical marijuana in Michigan. He thinks the state’s law should be amended so the drug can only be prescribed for a limited number of medical conditions.