Acute Cannabis Consumption Significantly Impairs Multiple Memory Functions, WSU Study Finds

A new study conducted by Washington State University (WSU) and published in the Journal of Psychopharmacology indicates that acute cannabis consumption can affect multiple memory functions. The research found that participants who consumed THC demonstrated significantly lower performance across most memory measures compared to a placebo group, with the strongest impacts observed in false memory and source memory systems.

"Participants who consumed THC demonstrated significantly lower performance across most memory measures compared to a placebo group, with the strongest impacts observed in false memory and source memory systems."

Study Methodology and Design

The study involved 120 regular cannabis users who participated in a double-blind experiment. Participants were randomly assigned to vaporize either placebo cannabis, 20 milligrams (mg) of THC, or 40 mg of THC.

Following consumption, participants completed approximately one hour of tests designed to assess various forms of memory. These included verbal, visuospatial, prospective, source, false, episodic content, and temporal order memory.

Key Findings: Widespread Memory Impairment

Participants who consumed cannabis exhibited significantly lower performance across the majority of memory tests compared to the placebo group. Out of 21 memory measures assessed, 15 showed significant differences.

The study also noted that there were no substantial differences in effects observed between participants who consumed 20 mg of THC and those who consumed 40 mg of THC. This suggests that even a moderate dose had a broad impact.

Specific Memory Systems Most Affected

The research identified particular areas of memory that were most affected by acute cannabis consumption:

False Memory

Cannabis users were more likely to recall words that had not been presented during a test. In one instance, participants heard lists of related words but not the central connecting word; those who consumed cannabis subsequently reported remembering both related and unrelated words that were not on the lists.

Source Memory

Participants consuming cannabis experienced increased difficulty remembering the origin of previously learned information. Impairments in source memory can affect the ability to distinguish if information came from a reliable source, a conversation, or online content.

Prospective Memory

Impairments were also found in prospective memory, defined as the ability to remember to perform future tasks. This includes crucial actions such as taking medication or attending appointments and meetings.

Episodic Content Memory: An Exception

One specific type of memory, episodic content memory (remembering personally experienced events), did not show a significant effect in this study.

Expert Commentary and Broader Implications

Carrie Cuttler, senior author of the study and an associate professor of psychology at WSU, stated that previous research often focused on a limited range of memory types. She noted that this study aimed to comprehensively examine various memory systems, observing that acute cannabis intoxication broadly disrupted most of them.

Cuttler also advised against being under the influence of cannabis when needing to remember to perform a future task. The disruptions identified, particularly in source memory, may also be relevant in contexts requiring accurate recall, such as eyewitness interviews.

Researchers noted that comprehensive studies on cannabis's acute cognitive effects have been limited, partly due to its federal classification as a Schedule I substance. The study's objective is to provide information for individuals to make informed decisions regarding the risks and benefits of cannabis use, especially amidst increasing cannabis use in certain states.