The potency of marijuana has been increasing significantly over the years. Studies have shown that the psychoactive ingredient in marijuana, called THC, has increased from 4% in 1995 to 17.1% in 2017.

This is concerning to scientists and healthcare professionals because THC can actually have the opposite effects on people at high doses then it does at low doses. “In general, people think, ‘Oh, I don’t have to worry about marijuana. It’s a safe drug,’ ” says Nora Volkow, director of the National Institute on Drug Abuse. “The notion that it is completely safe drug is incorrect when you start to address the consequences of this very high content of 9THC.” Psychotic episodes, decreased blood flow, and cannabinoid hyperemesis syndrome (where you can’t stop vomiting from consuming too much THC) all are leading to a three-fold increase of emergency room trips.

Read more about this concerning trend in the full NPR story.