Smoking marijuana is known to make people forgetful. Now however, research has shown that smoking the substance may also make people remember things that never happened. In particular, this finding raises concern within the criminal justice system, as it may lead to wrongful criminal convictions from inaccurate eyewitness testimonies.
Although previous research has already documented cannabis’s role in memory loss and memory distortion, until now, researchers did not know how the substance influences the creation of false or implanted memories. Thus, to understand this, a team of researchers from the Netherlands, Belgium Australia, Germany and the US set out to understand how THC impacts memory formation.
To do so, they recruited 64 occasional marijuana users, and asked each to undergo three experiments. On different days, each participant was asked to inhale the vapor of a single dose of marijuana or a placebo. Administered via a Volcano vaporizer- a device that inflates balloons with cannabis vapor, participants were asked to take their time to inhale the dosage over multiple breathes.
In the first experiment, after inhaling cannabis vapor, participants were asked to recall a list of words. Used to test the formation of “spontaneous” false memories, the researchers found that when participants who had smoked cannabis were exposed to words not shown on the original list, they were more likely than their unstoned counterparts to claim they had seen those words on the first list.
In the following experiments, participants were then asked to view a fight and perpetrate a theft using virtual reality. They were then given misinformation about what they saw and experienced, either through suggestive, leading questions from an interviewer or through testimonies by supposed witnesses. After this, each participant was then asked to recall what happened.
In the end, the researchers generally found that smoking marijuana increased the subject’s chances of creating false memories. In particular, they found that stoned participants had the highest rates of false memory formation following both leading and neutral questioning, while those in the theft scenario were more likely to respond “yes” to questions than their unstoned counterparts.
Although the research does not necessarily answer why being stoned makes it easier for false memories to form, it highlights important risk factors of smoking cannabis, especially in the criminal justice system. Lead author of the study, Lilian Kloft, a psychopharmacology research at Maastricht University in the Netherlands, said, “The next step for us is to investigate the effects of cannabis in a ‘false confession’ paradigm...False confessions are a major contributing cause to wrongful convictions and we cannot exclude that drug influence can magnify vulnerability for making a false confession.”