Smoking cannabis can do more than make thoughts hazy. It can change the way we store and recall memories.
Study Shows THC Affects Many Types of Memory
Scientists at Washington State University gave volunteers two doses of THC – 20 mg and 40 mg – and then tested their memory. The tests covered many areas, such as remembering words, pictures, future tasks, and where information came from.
People who used THC performed worse on most of the 21 memory tasks. In fact, they showed problems in 15 of those tests.
False Memories and Source Confusion
The biggest problems were with false memories and source memory. In one test, participants heard lists of related words, but the main keyword was never spoken. After the test, many who had taken THC claimed they remembered the missing word.
They also struggled to tell where a piece of information originally came from – whether it was from a friend, a book, or the internet.
Everyday Memory Tasks Take a Hit
THC also hurt prospective memory, the ability to remember to do things later. This includes tasks like taking medicine, going to a meeting, or stopping for groceries.
One type of memory – recalling personal experiences – did not change much, but more research is needed.
Why the Research Matters
Cannabis use is growing in many places, yet scientists still know little about its short‑term effects. Federal rules label cannabis as a Schedule I drug, which makes research harder.
The goal of the study is to help people understand the possible memory risks of cannabis so they can make better choices.