Jackson Leyden had always been a healthy kid. But in 2011, a few months after his eighth birthday, he began having seizures several times a day. His parents took him to more than 20 doctors. He tried more than a dozen medications. Nothing worked. Two years ago, the Leydens ... decided to see whether marijuana might help. Within a few days, he was having hardly any seizures," says his mother, Lisa. "I was shocked." Over the next few months, he stopped taking other medications. Not only did the medicine help, it did so without making him high. The strain of marijuana that Jackson takes is unusual: It contains high levels of cannabidiol, or CBD, one of the two main molecules in marijuana; the other is tetrahydrocannabinol, or THC. While THC is famously mind-altering, CBD is not. Over decades, researchers have found that THC may help treat pain, nausea, loss of appetite and other problems, while CBD was thought to be biologically inactive. But in the past 10 years ... dozens of studies have found evidence that the compound can treat epilepsy as well as a range of other illnesses, including anxiety, schizophrenia, heart disease and cancer. Now 13, Jackson ... continues to use marijuana every day. He still has seizures, but they are less severe and they occur once every week or two, down from around 200 a month before he started using cannabis. Although it doesn't make users high, CBD ... is classified by the federal government as a Schedule 1 drug [with] no accepted medical use.