More than half of all U.S. states have legalized cannabis, be it for medical purposes, recreational use, or both. The shelves of cannabis dispensaries offer an ever-widening array of gummies, drinks and joints.

Meanwhile, the federal government still considers most types of cannabis illegal.

A new report from the National Academies of Sciences, Engineering and Medicine, released this week, finds this disconnect between the states and the federal government is leading to fragmented policies, and risks to the public.