You've probably heard the anecdotal evidence for years from sources as varied as school anti-drug programs to Cheech and Chong. Now, a WSU study seems to confirm what we have heard about cannabis use and memory issues.
Before the study could even get underway, WSU researchers had to overcome one roadblock from the federal government, to make sure the study reflected the strength of the marijuana products available today. That's because federal rules regarding cannabis research require that the marijuana used in any studies come from one source.
But that marijuana, from the National Institute on Drug Abuse, is not nearly as potent as the pot currently for sale in Washington state dispensaries, with a level of just 6-10% of THC, the psychoactive ingredient in marijuana.
“In contrast, of course, in the dispensaries they're selling products that the flower exceeds 20 percent THC, and cannabis concentrates that can exceed 90 percent THC," says WSU College of Medicine researcher Carrie Cuttler.
She came up with a unique way to do the study. Using the popular Zoom app, Cuttler enlisted 80 volunteers to use cannabis they had purchased on their own legally from state outlets. Then, from the privacy of their own homes, subjects got high, and answered a battery of questions from researchers.
They were divided into a control group that didn't use cannabis, two groups that used cannabis flower with more than 20% THC, one containing CBD, a non-psychoactive component of cannabis and the other without CBD, and a group that vaped cannabis concentrates with more than 60% THC that included CBD.
The researchers found no effect on a range of decision-making tests, but did note certain types of memory issues.
Participants took several memory tests, which involve planning to do things at a later time, like making a doctor's appointment, and also temporal order memory tests, involving the order in which a sequence of events occurred.
But they did notice an effect of cannabis on source memory, where subjects were shown words and pictures on the screen and asked to recall them. They also found those who used cannabis had problems with a false memory test, where a number of related words would be presented, like bed, snore, and blanket, and were then asked later if the word sleep was included.
"We found that all three cannabis using groups were more likely to falsely recall completely words, words that we never presented to them and had nothing to do with the list or the themes of the list we presented to them," Cuttler said.
The research seemed to also contradict previous studies indicating that CBD, another ingredient in cannabis believed to have some therapeutic effects, might have a protective effect on memory.
“We found that participants who inhaled a cannabis joint containing CBD performed statistically comparable to the group that inhaled THC and no CBD. And the detrimental effects we found on those measures of free recall, we only found those in the group that inhaled the flower that contained both THC and CBD," she said.
Cuttler says the study also found no significant difference in memory results from those who smoked the 20% cannabis flower compared to those who inhaled high potency concentrates containing more than 60% THC. She says that seems to be because those using the concentrates chose to use less of the drug to achieve a similar level of intoxication and impairment.
Cuttler says they are currently starting a similar cannabis study that involves people suffering from ADHD, to see if there are any therapeutic effects of using the drug.