What A New High-Potency Cannabis Study Discovered About THC’s Relationship to Memory
How cannabis affects our memory has long been an important subject for researchers, but a recent study goes one step further than past trials by asking volunteers to use the cannabis often found in legal dispensaries: flower containing 20 percent or more THC, and concentrates reaching as high as 90 percent THC.
This new study, published in Scientific Reports in July 2021, also supports the findings from other research highlighting how cannabis use can induce false memories, which can have dire consequences during critical situations such as police interviews.
Study Uses High-Potency Cannabis and Concentrates
Washington State University researchers watched users through Zoom as they smoked high-potency cannabis flower or vaped concentrates the participants bought from dispensaries in Washington state, where recreational cannabis use is legal. A control group who didn’t use cannabis also participated. Researchers then gave the subjects a series of cognitive tests.
Researchers opted to give volunteers cannabis flower with 20 percent THC or higher to better imitate real-life sessions.
“It’s about external validity,” says Carrie Cuttler, a WSU assistant professor in the psychology department, and lead researcher of the study.
“Cannabis research in the U.S. is limited to 6 percent THC flower and rarely any concentrates, since cannabis’ Schedule I status doesn’t give us the access we really need to replicate real-world effects.”
No Impact on Performance, but Aspects of Memory Affected
The study concluded they couldn’t see an impact on the cannabis users’ performance on decision-making tests in comparison to a sober control group. Still, they uncovered some memory impairments related to free recall and false memories.
Free recall tests involved asking groups to remember a list of words and pictures presented to them, testing their short-term memory. Those who smoked cannabis flower performed worse on these tests because they couldn’t remember as many words or pictures that were shown to them compared to the sober group.
Turning to another memory test, the cannabis-using participants performed poorly on false memory: When given a new word and asked if it had been said before, they were more likely to say it had when it had not.
False Memory Could Lead to False Information
The implication of the false memory conclusion may seem inconsequential: So what if I incorrectly remember that I left my phone in the kitchen, when it really was never there all day?
Cuttler points to a consequence with higher stakes: “When police interview witnesses after a crime, they ideally want to ensure they are talking to sober people, because intoxicated witnesses using cannabis may be prone to bias and saying something happened when it didn’t.”
The WSU work echoes a major 2020 study run by Dr. Lilian Kloft, a postdoctoral researcher at University of Maastricht in the Netherlands. She and her team found that being under the influence of cannabis increased the potential to form false memories, compared to being sober.
Dr. Kloft told Cannabis Health: “Overall this showed us that when cannabis is present during a memory test during questioning by the police, cannabis could increase the risk to falsely go along with suggestive but also random questions about an event, increasing the risk that cannabis-intoxicated people may provide false information and thus potentially send an investigation in a wrong direction.”
But why does cannabis cause this to happen? While there hasn’t been a definitive answer to this query, Dr. Kloft offers a theory: “We can only speculate at this point … On a neurobiological level, THC activates CB1 receptors in our episodic memory center, the hippocampus, and such activation has been linked to the formation of ‘incidental’ or random associations in animal research.”
The THC-CB1 receptor link is also noted in previous research looking at cannabis use and memory, particularly in 2017 research on learning new information. The study authors wrote: “THC impairs recall of information encoded during drug effects. This result suggests that people should avoid learning new information under the influence of CB1R agonists. This is especially relevant to high school and college-age students who have to learn new information related to their academic demands.”
High-Potency Cannabis and Concentrates Didn’t Increase Harms
Interestingly, some studies believe that cannabis use can slow cognitive decline, although studies on mice have garnered the most recognition. This study noted how a single injection of THC in mice increased their level of Sirtuin-1, an enzyme that has been previously shown to be involved in neuroprotection and neuroplasticity.
The WSU study also points out an intriguing counter to the well-circulated idea that high-potency cannabis can be more harmful to our memory than cannabis with medium-grade THC levels. But Cuttler’s research doesn’t buoy those theories thanks to another conclusion: cognitive test scores didn’t vary between the group using 90 percent THC and the one smoking 20 percent THC.
“There’s been a lot of speculation that these really high-potency cannabis concentrates might magnify detrimental consequences, but there’s been almost zero research on cannabis concentrates which are freely available for people to use,” said Cuttler.
“I want to see way more research before we come to any general conclusion, but it is encouraging to see that the concentrates didn’t increase harms.”
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