A new study finds that smoking cannabis may alter how memories form and are recalled, according to researchers at Washington State University.

Cannabis users were much more likely to recall words that were never shown and struggled with tasks like remembering to do something later.

Researchers found that THC disrupts many different memory systems at once.

Published in the Journal of Psychopharmacology, the results indicate that cannabis affects not only simple recall, like remembering a list of words, but also several forms of memory that people rely on throughout the day. These include remembering appointments, keeping track of conversations, and identifying where information originates from.

Researchers were also surprised to see no meaningful differences between participants who consumed 20 milligrams of THC and those who consumed 40 milligrams. This finding suggests that even moderate amounts of THC may significantly interfere with memory.

“Most previous studies have only looked at one or two types of memory, like recalling lists of words,” said Carrie Cuttler, senior author of the study and an associate professor of psychology at WSU. “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.”

Cuttler and co-author Ryan McLaughlin, an associate professor in the Department of Integrative Physiology and Neuroscience at WSU, recruited 120 regular cannabis users. Participants were randomly assigned to vaporize placebo cannabis, 20 milligrams of THC, or 40 milligrams of THC in a double-blind experiment.

Hour-long memory assessments measured several types of memory, including verbal, visuospatial, prospective, source, false, episodic content, and temporal order memory.

Those who had consumed cannabis were more likely to say they remembered hearing words that had not been presented.

“I found 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 sometimes they were completely unrelated.”

Issues were most pronounced in false memory and source memory, which help people accurately recall information and determine where that information came from.

Researchers said that problems with source memory can make it harder to determine whether information came from a trusted source, a conversation, or something encountered online, and that these kinds of memory distortions could have serious implications in situations where accurate recall is essential.

Impairments in prospective memory, which is the ability to remember to perform tasks in the future, were also observed. This type of memory is involved in everyday responsibilities such as taking medication, attending meetings, or stopping at the store on the way home, according to the researchers.

“These are things we rely on constantly in our day-to-day lives,” Cuttler said. “If you have something you need to remember to do later, you probably don’t want to be high at the time you need to remember to do it.”

Information provided by Washington State University. (2026, March 11). Cannabis study finds THC can create false memories. ScienceDaily. Retrieved March 11, 2026, from www.sciencedaily.com/releases/2026/03/260311004711.htm