A new study from Washington State University shows that consuming THC leads to false memories and disrupts various everyday memory functions. Participants who used cannabis recalled nonexistent words and struggled with tasks like remembering future actions. The research highlights effects even at moderate doses.
Researchers at Washington State University conducted a detailed experiment on how cannabis affects memory, publishing their findings in the Journal of Psychopharmacology. The study involved 120 regular cannabis users who were randomly assigned to vaporize either a placebo, 20 milligrams of THC, or 40 milligrams of THC in a double-blind setup. After consumption, participants underwent about an hour of tests assessing verbal, visuospatial, prospective, source, false, episodic content, and temporal order memory.
The results showed significant impairments across most memory types, with differences in 15 out of 21 tests compared to the placebo group. Notably, cannabis users were more prone to false memories, such as recalling words from themed lists that were never presented. "I found it was really common for people to come up with words that were never on the list," said Carrie Cuttler, senior author and associate professor of psychology at WSU.
Source memory, which helps identify the origin of information, also suffered, potentially complicating recall from trusted sources or conversations. Prospective memory—remembering to perform future tasks like taking medication—was similarly affected. "These are things we rely on constantly in our day-to-day lives," Cuttler noted. "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."
Surprisingly, no substantial differences emerged between the 20-milligram and 40-milligram doses, indicating moderate THC levels can cause notable disruptions. Episodic content memory, related to personal experiences, showed no significant impact in this study, though further research is recommended. The work underscores gaps in understanding cannabis's short-term cognitive effects amid growing legalization in places like Washington state, where federal restrictions have limited prior studies. Cuttler emphasized the aim: "The goal is to help people make informed decisions about the risks and benefits."