Here’s something to think about before lighting up: frequent marijuana use might mess with your brain’s ability to remember important stuff. A recent study, one of the largest of its kind, found that the more often people use cannabis, the harder it becomes for them to hold onto and use short-term information—like following a conversation or checking a blind spot while driving.

Researchers say working memory, the brain’s ability to keep info handy for quick tasks, takes a hit with regular use. For example, forgetting a grocery list or zoning out during a chat with your boss? That might not just be a “bad day”—it could be linked to how much weed you’ve been smoking.

The study dug into data from over 1,000 people, looking at brain scans and cognitive tests. Turns out, heavy users—those who’ve lit up more than 1,000 times in their lives—showed reduced brain activity in areas tied to memory and decision-making. Even more surprising? Around 63% of heavy users struggled with working memory tasks compared to non-users.

But here’s the kicker: it’s not just about how recently someone’s used marijuana. Chronic, long-term use seems to have a bigger impact than occasional or recent use. Even if someone stopped smoking years ago, their memory issues might stick around.

The study didn’t prove that marijuana causes these problems—it just found a strong link. Researchers also couldn’t say if quitting entirely would help the brain bounce back. “Some studies suggest memory improves after a month of not using,” one expert said, “but for chronic users, it’s still unclear.”

The findings raise more questions, like whether other factors—like existing mental health conditions—play a role. And while the study didn’t track how people consumed cannabis, smoking was likely the main method since the data was collected before vaping and edibles became widespread.

So, if you’re a regular user, this might be a heads-up to take it easy. Your brain—and your memory—will thank you.