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WSU Study Finds Acute Cannabis Intoxication Impairs Performance on Multiple Memory Tests

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Study: Acute Cannabis Intoxication Impairs Memory Performance

A study from Washington State University (WSU) has found that acute cannabis intoxication can impair performance across a range of memory tests. The research, involving 120 regular users, observed significant differences in 15 out of 21 memory measures compared to a placebo group, with notable effects on false memory and source memory tasks.

Study Design and Participants

The research, published in the Journal of Psychopharmacology, was a double-blind, placebo-controlled experiment. The 120 participants, all regular cannabis users, were randomly assigned to one of three groups:

  • One that vaporized a placebo.
  • One that vaporized 20 milligrams of THC.
  • One that vaporized 40 milligrams of THC.

Approximately one hour after consumption, participants completed a battery of tests designed to assess multiple memory systems.

Key Findings on Memory Performance

The study assessed verbal, visuospatial, prospective, source, false, episodic content, and temporal order memory. Participants who consumed cannabis showed significantly lower performance on most measures compared to the placebo group.

Notable impairments were observed in false memory and source memory tasks.

  • False Memory: In tests where participants heard lists of related words, those who had consumed cannabis were more likely to report remembering words that were not presented. These included words related to the list's theme and words that were unrelated.
  • Source Memory: Cannabis users had increased difficulty accurately recalling the origin of previously learned information, such as whether details came from a specific source or conversation.
  • Prospective Memory: Impairment was observed in the ability to remember to perform future tasks, a function relevant to activities like taking medication or attending appointments.
  • Episodic Content Memory: One type of memory, episodic content memory (recalling personally experienced events), did not show a significant effect in this study.

Dosage and Research Context

Researchers reported no meaningful differences in the degree of memory impairment between the group that consumed 20 milligrams of THC and the group that consumed 40 milligrams.

The study's authors note that comprehensive research on the acute cognitive effects of cannabis has been limited historically due to its federal classification as a Schedule I substance in the United States. According to the researchers, the objective of the study is to provide information for individuals to make informed decisions regarding cannabis use.