Christopher Moraff, writing for The Daily Beast:
In 2011 and 2012, faced with a spike in emergency room visits, the Drug Enforcement Administration banned a handful of the compounds. Chemists continued tweaking the drugs to skirt ever-evolving synthetic drug laws, but since peaking in 2015, calls to poison centers for synthetic marijuana dropped by more than half. But over the past year K2 has made a comeback; and a recent spate of poisonings has public health officials worried.
"Scary as hell" is right. Crazy to think that although synthetic cannabinoids were relatively unpopular the past few years, they really do seem to be experiencing a full-fledged comeback now—especially among opioid users.