Student Research

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Cannabis increases susceptibility to false memory

Article by Lilian Kloft, Henry Otgaar, Arjan Blokland, Lauren A. Monds, Stefan W. Toennes, Elizabeth F. Loftus, and Johannes G. Ramaekers
Summary by Maria Poblete, 3rd year neuroscience student.

Δ9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, is an agonist of cannabinoid receptor type 1 (CB1R). Previous studies demonstrate THC-associated deficits in memory and decision making, an effect thought to result from THC-associated hippocampal CB1R activation. An increase in false memories can be predicted by these elevated levels, mediated by increased incidental association (behavioral learning from misleading, unimportant stimuli). Cannabis-associated false memories have implications in the justice system, raising the question of intoxicated eyewitness and perpetrator reliability during investigative interviews. To determine the magnitude of THC’s impact on associative memory and false-memory production, Kloft et al. assessed memory rates in healthy, occasional cannabis users.

This double-blind, placebo-controlled study compared false-memory susceptibility after exposure to placebo cannabis and active cannabis (300 μg/kg THC) vapor, both immediately and one week after administration. On separate days, participants inhaled a single dose of either placebo or THC vapor before assessment. The trial used three assessments: an associative memory test and two virtual reality (VR) scenarios. The associative memory test assessed the Deese/Roediger-McDermott (DRM) paradigm; the paradigm describes rates of incorrectly recalling words not actually present in a list of suggestively related words. The two VR scenarios required participants to act as an eyewitness and perpetrator in a simulation, undergo a series of suggestive misleading questions in interview, and take a memory test.

In all three tests, THC administration increased false-memory rates during the immediate stage of testing compared to placebo administration. In the DRM assessment, THC decreased memory accuracy both immediately and after one week compared to the placebo. However, in both VR scenarios, THC only decreased memory accuracy in the immediate stage of recall compared to the placebo; THC’s effects were no longer present after one week of

Overall, the study demonstrated higher false memory incidence immediately after THC exposure. This implies that individuals under THC’s influence may be at higher risk of incorrect memory recall. This effect potentially threatens investigative settings, especially if justice systems use suggestive questions that can mislead interviewees. Future actions may require labeling THC-intoxicated individuals as a vulnerable group, with children and the elderly.