Does Cannabis Affect Short-term Memory?

Does Cannabis Affect Short-term Memory - woman's memory fades

We've all seen it before: the sad movie stereotype of the goofy, absent-minded stoner. He's usually warm-hearted but stupid, and almost invariably has a serious short-term memory problem. You might even know one of these lovable screw-ups yourself. If you're a cannabis consumer, you may wonder if you might emulate the archetype yourself with just a few too many joints. Here's a common question from consumers of all experience levels: Does cannabis affect short-term memory? What about other types of memory? The studies may surprise you.  

Temporary Effects of Cannabis on Memory

It would be silly to suggest marijuana does nothing at all to your memory. Anyone who has smoked (or vaped, or eaten) enough THC knows that a good strong strain will have you forgetting the rest of your sentence after the first two words. The way THC interacts with your CB1 receptors affects a myriad of regulated physiological functions, including memory.

THC can alter your memory functions in two main areas: Formation of new memories, and short-term recall. While under the influence of marijuana, your brain has to work harder to form new memories. It's nothing compared to the blackouts that plague heavy drinkers, but some potential new memories do slip through the cracks when you're high. You'll also have some noticeable difficulty remembering odds and ends while under the influence. You're unlikely to forget your address or phone number, but you might forget those plans you just made with a friend.

At least one study reports that these effects last during and immediately after the high, and the cognitive function returns to normal levels about two hours after someone stops feeling high.  

Lasting Effects on Memory

Knowing that weed affects memory during use, Swiss researchers asked the next logical question: Does cannabis affect short-term memory in the long-term Professor Reto Auer at the University of Lausanne gathered a team of researchers and set in for a long-haul study. Over 25 years, the researchers gathered and analyzed data on the cannabis consumption of almost 3,400 U.S. residents. After the 25 years were up, study participants ran a gauntlet of tests gauging memory, focus, and decision-making ability. 

The study results are based on usage measurements they call "marijuana-years". One marijuana-year of use is equivalent to consuming cannabis every single day for one year. Scale it back to smoking every other day for one year, and that's two marijuana-years of use. The study concludes that five marijuana-years of use is the threshold for long-term effects on short-term memory. The study results show plainly that more exposure to cannabis equals more memory problems  

Does Cannabis Affect Short-term Memory?
A Study

Imagine that you have 20 people, divided into two groups of 10. You give them 15 words that they have to memorize, then leave them alone for 25 minutes afterward. After the time's up, you ask them to list as many of the 15 words they can remember.  

In the study, the first group consists of people who aren't cannabis consumers, or who partake infrequently. This group got an average of nine words correct. The second group consists of people with five marijuana-years of consumption under their belts. The second group remembered one less word than their non-smoking counterparts, and the effect is cumulative. For every five marijuana-years of use, study participants forgot one more word that their counterparts could remember.  

It's crucial to note this particular form of short-term memory, called "verbal memory", was the only field affected. Other indicators of short-term memory performance, such as processing speed and focus, showed negligible signs of impact from heavy consumption of cannabis. Only eight percent of the study subjects actually had more than five marijuana-years of consumption, and there's no way to be sure the correlation is completely 100 percent causal.  

Avoiding Memory Loss from Cannabis

Does cannabis affect short-term memory? Yes. But for the damage to occur, you have to sink in a lot more time and money into toking than most people possess. If you're concerned about a decline in your short-term memory, the only thing you can do is stop consuming so much cannabis. 

Tolerance breaks don't just lower your tolerance and save you money, they help your brain reset and rebalance. The Swiss study did not take into account what happened to the heaviest consumers' verbal memory if they stopped smoking every day. But it's not outlandish to consider that, like other long-term effects of cannabis, the decline in memory might reverse in some part. At the very least, cutting back the days per week you smoke will reduce your lifetime marijuana-years of use and thereby reduce the negative effects.