The largest study yet into the effects of cannabis on the brains of 18- to 36-year-olds has found that the drug can reduce brain function during cognitive tests. The findings will help people to make an informed decision about the pros and cons of using cannabis.

A new study published today in JAMA Network Open explores the effects of both recent and lifetime cannabis use on brain function during cognitive tasks.

Cannabis use can significantly impact the part of the brain responsible for following instructions, responding during conversations, or remembering a question long enough to answer it. This type of cognitive function is a form of short-term memory called working memory.

A study of over 1,000 young adults reveals that both recent and heavy lifetime cannabis use reduce brain activity in regions critical for working memory, including the prefrontal cortex and anterior insula.

The myth that cannabis is harmless because it’s natural has been further debunked—by scientists in a pot-friendly state.