A new study found that acute cannabis intoxication can disrupt most human memory systems. Researchers discovered that exposure to the psychoactive compound tetrahydrocannabinol (THC) affects not only basic memory but also several cognitive processes used in daily life, such as remembering future tasks, tracking conversations, and identifying sources of information.

The study was conducted by specialists at Washington State University, with results published in the Journal of Psychopharmacology.

The experiment included 120 regular cannabis users, randomly divided into three groups: one received a placebo, another 20 mg of THC, and the third 40 mg of THC. Participants then completed about an hour of memory tests.

Researchers assessed multiple types of memory, including verbal, visuospatial, prospective, source, false, episodic, and order memory. Results showed that participants who consumed cannabis performed significantly worse on most tests. In total, 15 of the 21 memory measures evaluated showed impairment.

The strongest effects were observed in false memory and source memory systems. Under the influence of cannabis, participants were more likely to “remember” words or events that were never presented to them. For example, in a test where participants heard lists of related words with a key word omitted, many later believed they had heard the missing word.

Interestingly, researchers found no significant difference between the moderate and higher THC doses, indicating that even relatively small amounts of cannabis can substantially impair memory.

According to the authors, most previous studies examined only one or two aspects of memory, such as word recall. This study is the first to simultaneously assess multiple memory systems, demonstrating that acute cannabis intoxication can impair most memory functions at the same time.