Cannabis intoxication can create memories of events that never happened, a new research has found. This can lead to disastrous results in legal cases where witness or perpetrator was under the influence of cannabis.
“We show across different paradigms that cannabis consistently increases susceptibility to false memories. The results have implications for police, legal professionals, and policymakers with regard to the treatment of cannabis-intoxicated witnesses and suspects and the validity of their statements,” says the research.
Cannabis can lead to both spontaneous false memories which arise due to internal cognitive processes and suggestion-based false memories which occur due to external suggestion.
The research says that cannabis-intoxicated individuals might have to be treated as a vulnerable group, similar to child or elderly witnesses/suspects.
“As a potential factor impacting memory, cannabis intoxication is an issue of particular interest from a legal perspective. That is, testimonies by eyewitnesses or suspects are oftentimes the only piece of evidence that triers of fact can use for legal decision making, and, thus, gathering reliable testimony is crucial. However, memory performance is imperfect, resulting sometimes in false memories (i.e., memories of nonexperienced events/details), and such false memories can have disastrous consequences in legal cases (e.g., wrongful convictions or false accusations),” says the research.
While cannabis robustly increases false memory at the retrieval stage, some effects persist even after one week when people are sober again, indicating that THC-induced encoding (i.e., intake of information) is also error prone.
The research found that cannabis-intoxicated people seemed to show a tendency toward more liberal responding under conditions of uncertainty. It says an increase in irrelevant associations might stem from increased incidental learning due to activation of hippocampal CB1 receptors.
Cognitive effects of cannabis include a loosening of associations, fragmentation of thought, and heightened distractibility. “Such reductions in focus and increments in mental activity could well account for the increase in false recognitions of irrelevant or unrelated words or events on all memory tasks,” says the research.