Does Marijuana Actually Ruin Your Memory?

In the short term, marijuana hinders your learning ability, but doesn’t seem to cause long-term impairment.

Marijuana makes you dumb. At least according to the tired trope surrounding its use. Back in the day, stoners were considered slackers and anyone who smoked weed was on a one-way ticket to Loserville.

Today, many of those stigmas have fallen away. But some still linger in the popular consciousness, like the perception that every hit on a joint results in a lower IQ. But does smoking marijuana actually make you stupid?

Not really, according to a review published in the journal Neuropsychology. Canadian researchers Scot Purdon and Daniel Krzyzanowski aimed to better understand what long-term cognitive effects cannabis could have on users. They analyzed 23 previous studies to determine if marijuana abstinence had any impact on verbal learning and memory abilities.

Based on available literature, they wrote, whatever impairment marijuana use inflicted upon memory and verbal learning “appear to resolve between 7 and 28 days of sustained abstinence.” However, they added, “years of regular use were inversely related to longer periods of abstinence and verbal learning performance, undermining a confident inference that abstinence alone has direct benefits to verbal learning and memory.”

This isn’t the first research conducted by Purdon that focuses on marijuana and memory. In 2018, Purdon conducted a study that found marijuana hinders the verbal learning — the ability to read and retain information — for up to 24 hours after usage. Within one to three days, that impairment is reduced by half.

What does that mean for general users? If you’re cramming for an exam or need to remember a presentation, it’s probably best not to use marijuana a day before learning the information. And if you’re ever worried your cannabis habit is causing you to become forgetful, take a week off.