A British pharmaceutical company is getting closer to a decision on whether the U.S government will approve the first prescription drug derived from the marijuana plant, but parents who for years have used cannabis to treat severe forms of epilepsy in their children are feeling more cautious than celebratory.

The U.S. Food and Drug Administration is expected to decide by the end of the month whether to approve GW Pharmaceuticals’ Epidiolex. It’s a purified form of cannabidiol — a component of cannabis that doesn’t get users high — to treat Dravet and Lennox-Gastaut syndromes in kids. Both forms of epilepsy are rare.

Cannabidiol’s effect on a variety of health conditions is frequently touted, but there is still little evidence to back up advocates’ personal experiences. The U.S. Drug Enforcement Administration has long categorized cannabis as a Schedule I drug, a category with “no currently accepted medical use and a high potential for abuse.” That strictly limits research on potential medical uses for cannabis or the chemicals in it, including cannabidiol, or CBD.

But for years, parents desperate to find anything to help their children have turned to the marijuana-based products made legal by a growing number of states. [Read more at Colorado Public Radio]