Cannabis is widely used in many parts of the world, especially as laws change and the drug becomes more accessible.
Many people know that cannabis can affect memory in the short term.
For example, users may forget conversations, lose track of what they were doing, or struggle to recall details.
However, new research suggests that cannabis may affect memory in more complex ways than previously understood.
A recent study from Washington State University found that cannabis can not only weaken memory but may also change the way memories are formed and recalled.
The research, published in the journal Journal of Psychopharmacology, showed that people who consumed THC—the main psychoactive compound in cannabis—were more likely to remember things that never actually happened.
This means that cannabis may increase what scientists call “false memories,” which occur when people believe they remember something accurately even though the event never took place.
The study was led by Carrie Cuttler, an associate professor of psychology at Washington State University, along with Ryan McLaughlin, an associate professor in the university’s Department of Integrative Physiology and Neuroscience. The researchers wanted to better understand how cannabis affects different types of memory that people rely on in everyday life.
Previous studies have usually focused on just one or two types of memory, such as recalling a list of words. However, memory is a complex system that involves several different processes working together. The research team designed a study that examined many types of memory at once.
To conduct the experiment, the researchers recruited 120 adults who were regular cannabis users. Participants were randomly assigned to one of three groups. One group used cannabis with no THC, which served as the placebo group. The second group consumed cannabis containing 20 milligrams of THC, while the third group consumed cannabis with 40 milligrams of THC.
The study used a double-blind design, meaning that neither the participants nor the researchers knew which group each person was in during the experiment. This approach helps prevent bias and improves the reliability of the results.
Participants vaporized the cannabis and then completed about one hour of cognitive tests. These tests were designed to measure several different types of memory, including verbal memory, visual and spatial memory, the ability to remember future tasks, and the ability to recall where information came from.
The results showed that cannabis affected memory across many different areas. Participants who consumed THC performed worse than those in the placebo group on most of the memory tests. In total, significant differences were observed in 15 of the 21 memory measures studied.
One of the most noticeable effects was in false memory. In one part of the experiment, participants listened to lists of related words, but the key word that linked them together was never actually spoken. Later, participants were asked to recall the words they had heard.
People who had consumed cannabis were much more likely to report remembering the missing key word—even though it had never been presented. In some cases, they also reported unrelated words that had not appeared on the list at all.
The researchers said this finding shows how cannabis may alter the brain’s ability to correctly store and retrieve information.
Another type of memory affected was called source memory. Source memory helps people remember where a piece of information came from. For example, it helps us recall whether we learned something from a conversation, a book, or something we saw online.
When source memory is disrupted, people may remember information but struggle to identify its origin. This can create confusion and make it harder to judge whether the information is trustworthy.
Problems with source memory can be especially important in situations where accurate recall matters, such as eyewitness testimony in legal cases. If memory is influenced by cannabis, it could increase the chances of mistakes or suggestibility during interviews.
The study also found that cannabis impaired prospective memory. This type of memory allows people to remember to perform tasks in the future. Everyday examples include remembering to take medication, attend an appointment, or stop at the store on the way home.
Prospective memory plays an important role in daily life because it helps people plan and follow through on tasks. When this system is disrupted, people may forget responsibilities or fail to complete important actions.
Interestingly, the researchers found little difference between the effects of 20 milligrams and 40 milligrams of THC. This suggests that even moderate doses of cannabis may significantly affect memory performance.
One type of memory, known as episodic content memory, appeared less affected in this study. Episodic memory involves remembering personal experiences, such as recalling what happened during a specific event. However, the researchers noted that more studies are needed before drawing firm conclusions about how cannabis affects this type of memory.
The study comes at a time when cannabis use is becoming more common in many regions, including parts of the United States and Canada where recreational use has been legalized. In Washington State, where the study took place, cannabis use is widespread.
Despite this growing acceptance, scientists say many of the drug’s short-term cognitive effects are still not fully understood. One reason for this is that cannabis remains classified as a Schedule I substance under United States federal law, which has historically limited research opportunities.
Professor Cuttler said the goal of the study was not to discourage cannabis use but to provide clearer information about its effects.
Understanding how cannabis affects memory can help people make more informed choices, especially when they need to perform tasks that require careful thinking, accurate recall, or responsibility.
The researchers believe future studies will continue to explore how cannabis affects the brain and how long these memory changes may last.
Overall, the findings suggest that cannabis intoxication can disrupt several important memory systems that people rely on every day. While the effects may be temporary, they could influence decision-making, communication, and the ability to complete important tasks.
If you care about cannabis, please read studies that what you need to know about cannabis and heart attack, and CBD from cannabis may help inhibit COVID-19 infection.
For more information about cannabis, please see recent studies that medical cannabis could help reduce depression, and results showing this stuff in cannabis may protect aging brain, treat Alzheimer’s.
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