• Posted March 22, 2026

Don't Forget This: Study Shows Cannabis Exacts a Toll on Your Memory

Got something important you don’t dare forget — like taking your heart medication, turning off the stove or a big date? 

Here’s some friendly advice from Carrie Cuttler, a researcher at Washington State University in Pullman.

"You probably don’t want to be high at the time you need to remember to do it," said Cuttler, an associate professor of psychology and co-author of a new study looking at what cannabis does to your memory.

In a study of 120 regular cannabis users, she and her colleague Ryan McLaughlin found that smoking weed disrupted multiple memory systems at the same time. 

In fact, they reported, THC, the chemical in cannabis that makes you high, may do even more than make you a tad forgetful. It can even create new memories — of things that never happened.

The findings were recently published in the Journal of Psychopharmacology.

The research suggests that cannabis affects not only simple recall — like remembering a list of words — but kinds of memories people rely on to get through the day.

Among them: keeping track of conversations, remembering appointments and knowing where information originally came from.

And the fuzzy recall wasn’t any different whether participants consumed 20 milligrams of THC or twice as much, suggesting that even moderate use may significantly mess with memory.

"Most previous studies have only looked at one or two types of memory, like recalling lists of words," Cuttler said in a news release. "This is the first study to comprehensively examine many different memory systems at once, and what we found is that acute cannabis intoxication appears to broadly disrupt most of them."

For the study, Cuttler’s team divided the 120 cannabis users into three groups: One took a placebo; another consumed 20 milligrams of THC; the third, 40 milligrams. 

Then, they completed an hour’s worth of memory assessments. These tests gauged several kinds of memory, from verbal to visual, false memory and the ability to recall the sequence, timing and order of events.

On 15 of 21 tests, participants who used cannabis did significantly worse than the placebo group.

The biggest effects were in false memory and source memory, which help people recall information correctly as well as where it came from, researchers found.

In one test, participants listened to lists of related words. Though the keyword linking them was never mentioned, the cannabis users were more likely to say they heard words that were never presented.

"It was really common for people to come up with words that were never on the list," Cuttler said. "Sometimes they were related to the theme of the list, and soemtimes they were completely unrelated."

Further, the cannabis users struggled to identify where previously learned information came from. Researchers said problems with source memory can make it harder to determine whether information came from a conversation, a trusted source or something online.

"These kinds of memory distortions could have serious implications in situations where accurate recall is essential," they said in a news release.

Also observed were flaws in participants' ability to remember to perform scheduled tasks — like taking medicine or ferrying junior to baseball practice.

There was, however, no significant effect on participants’ recall of personal experiences — which is called episodic content memory.

The study dovetails with legalization of cannabis in many states, including Washington.

"We’re living in a state where cannabis use is very common, but there’s still a lot we don’t know about its acute effects," Cuttler concluded. "The goal is to help people make informed decisions about the risks and benefits."

More information

Harvard Health has more about the effects of marijuana on your memory.

SOURCE: Washington State University, news release, March 11, 2026