Highly potent cannabis may cause memory issues for marijuana smokers and vapers

PULLMAN, Wash. — Recreational marijuana use is becoming a common site throughout the United States. Although several states are now allowing the sale of highly potent varieties of cannabis, scientists say they’re still playing catch-up when it comes to knowing how these products affect the human body. Now, a new study finds high-strength weed may leave users’ memories a little foggy. Researchers from Washington State University report that people who either smoke or vape potent marijuana perform worse in various memory tests compared to sober individuals.

You may be asking: if states are legalizing cannabis, why are scientists behind on researching its health benefits or impairments? One of the big reasons is the U.S. federal government still classifies it as a Schedule 1 drug. Under those rules, scientists can only test cannabis products with low levels of tetrahydrocannabinol (THC) – the drug’s main psychoactive ingredient. However, the WSU team notes recreational marijuana products are much stronger.

“Because of federal restrictions to researchers, it was just not possible to study the acute effects of these high-potency products,” says lead researcher and WSU psychologist Carrie Cuttler in a university release. “The general population in states where cannabis is legal has very easy access to a wide array of high- potency cannabis products, including extremely high-potency cannabis concentrates which can exceed 90% THC, and we’ve been limited to studying the whole plant with under 10% THC.”

Turning to the people to test recreational marijuana

To test the impact of high-potency cannabis, researchers recruited 80 participants who the team observed through Zoom video chats. Each of these marijuana users purchased their own weed and used it in their own homes in Washington state, where recreational use is legal.

The scientists note these volunteers never entered the WSU labs and were not reimbursed for buying the marijuana. They did, however, receive Amazon gift cards as compensation for their time in the study.

Study authors broke the group down into four separate categories. One used cannabis flower containing more than 20 percent THC and cannabidiol (CBD), the drug’s non-psychoactive component. Another group also used highly-potent cannabis flower which did not contain CBD.

The third group vaped cannabis concentrates that had over 60 percent THC and CBD. The final group stayed sober throughout the experiment.

Cannabis won’t impact decisions, but may affect memory

After giving each group a series of cognitive tests, results show smoking and vaping marijuana appears to have no impact on how people perform in decision-making tests. On the other hand, using the drug did lead to memory impairments, including problems with free recall, source memory, and false memories.

Specifically, cannabis use did not give participants trouble with decisions that deal with risk perception and the confidence in their knowledge. Marijuana also did not appear to affect prospective memory, which is the ability to remember to do things later – like going to an appointment. Cannabis users also did well in remembering the order in which events take place.

Highly potent marijuana flower containing CBD did disrupt users’ ability to recall certain details, such as how many words or pictures researchers showed them. Study authors note this is a new finding, different from previous studies which suggested that cannabis with CBD may help memory.

The group using cannabis without CBD and the group vaping cannabis concentrates also struggled with source memory — the ability to distinguish how previously learned information was presented.

Lastly, all three of the cannabis groups performed worse in false memory tests compared to the sober group. Those smoking and vaping marijuana were more likely to think they heard a new word when they actually had not.

Vaping and smoking marijuana leads to the same results

One surprising find from the study, researchers say people vaping concentrates with over 60 percent THC had similar results to participants smoking cannabis flower around 20 percent THC. The team believes this may be because those who buy high-potency concentrates use less of the drug to achieve the same “high” as smoking cannabis.

“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,” Cuttler concludes. “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.”

Currently, 19 states and Washington D.C. have legalized cannabis for recreational use. The U.S. Drug Enforcement Administration says it may allow some companies to start growing their own cannabis for research studies.

The team published their findings in the journal Scientific Reports.

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