Researchers Examine THC’s Impact on Memory
A new study from Washington State University suggests that cannabis may not only impair memory but also increase the likelihood of forming false memories that feel real.
Researchers recruited 120 regular cannabis users and randomly assigned them to inhale either cannabis containing 20 or 40 milligrams of THC, the main psychoactive compound, or a placebo. Participants then completed 21 different memory tests, including measures rarely used in previous cannabis research.
The findings showed that about 70% of participants experienced some level of memory impairment after consuming THC. The most notable effect was an increased susceptibility to recalling events or details that never occurred.
Why False Memories Occur
Scientists believe false memories arise when the brain reconstructs incomplete information. THC appears to weaken detailed recollection while preserving a general sense of familiarity, which can make inaccurate memories feel convincing.
The researchers reported that, compared to placebo, cannabis increased false memories and impaired several types of memory, including verbal, visuospatial, working, source and temporal order memory. No significant differences were observed between moderate and higher THC doses.
Carrie Cuttler, associate professor and co-author of the 2026 study, explained that THC disrupts neural pathways involved in memory formation and recall. When those pathways are overstimulated, accurate reconstruction becomes more difficult.
Broader Cognitive Effects
The study authors noted that this was the first research to detect acute cannabis effects on prospective memory and temporal order memory, which are considered important for daily functioning.
They concluded that short-term cannabis use may broadly affect multiple domains of memory rather than selectively impairing only a few areas.
Cuttler added that acute alcohol intoxication is generally more disruptive to memory than cannabis. She also noted that THC-related effects can diminish significantly after sustained abstinence.
Common Side Effects of Cannabis
In addition to memory changes, commonly reported short-term effects of marijuana use include altered sensory perception, changes in mood, slowed reaction time, impaired coordination, confusion, dizziness and, in some cases, panic reactions.
Cannabis remains classified as a Class B drug in the UK, though it continues to be the most commonly used illicit substance in England and Wales.