Washington State University (WSU) researchers using Zoom to test the effects of high-THC cannabis on recreational users in the US have found it had no impact on their performance in decision-making tests compared to a control group.

As reported by News Medical Life Sciences, the team observed the cohort via the video conferencing app as they smoked high-potency cannabis flower or vaped concentrates purchased from dispensaries in Washington state, where recreational use is legal.

They then gave the subjects a series of cognitive tests and found no impact on their decision-making performance compared to a control group. However, they did find some memory impairments related to free recall, source memory and false memories.

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While the findings are in line with previous research on low-potency cannabis, the study is one of the few to investigate cannabis containing more than 10% THC, and is only the second known study to examine the effect of cannabis concentrates.

Until recently, US researchers studying cannabis were limited to using low-potency plants of around 6% THC supplied by the National Institute of Drug Abuse. In June, the US Drug Enforcement Administration indicated it may allow some companies to start growing cannabis for research purposes.

The study, which started in 2018, was able to comply with federal guidelines because participants bought their own products and used them in their own homes.

The 80 participants were over 21 and experienced cannabis users who reported previous no negative reactions to the drug. They were divided into four groups. Two used cannabis flower with more than 20% THC (one with, and one without, CBD), another group vaped cannabis concentrates with more than 60% THC that included CBD, and a fourth group remained sober.

For all cannabis-using groups, the researchers found no effect on a range of decision-making tests including risk perception and confidence in knowledge. There were also no significant differences between the cannabis-using and sober groups on memory tests, including prospective memory – the ability to remember to do things at a later time.

The cannabis-using participants also did well on temporal order memory – the ability to remember the sequence of previous events.

“It is encouraging to see that the concentrates didn’t increase harms.”

WSU lead researcher and psychologist Carrie Cuttler

However, the groups that smoked cannabis flower with CBD did worse on verbal free recall trials – they were unable to recall as many words or pictures that were shown to them compared to the sober group.

This finding was contrary to a small number of previous studies indicating CBD might have a protective effect on memory.

The groups that used cannabis without CBD and the group that used concentrates performed worse on a measure of source memory – being able to distinguish the way previously learned information was presented.

Carrie Cuttler

Finally, all three cannabis-using groups did poorly on a false memory test – when given a new word and asked if it had been presented before, they were more likely to say it had when it hadn’t.

There was also an unexpected finding: people who vaped the high-potency concentrates with more than 60% THC performed comparably to those who smoked cannabis flower. This may have been because they tended to self-titrate – using less of the drug to achieve a similar level of intoxication and impairment as the people who smoked the less-potent cannabis flower.

WSU lead researcher and psychologist Carrie Cuttler said: “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.

“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.”

Prior to launching Cannabiz, Martin was co-founder and CEO of Asia-Pac’s leading B2B media and marketing information brand Mumbrella, overseeing its sale to Diversified Communications in 2017. A journalist...