Health Information Marijuana

How Does Marijuana Affect Memory?

Marijuana and losing your memory have long been thought to go hand in hand. Can’t remember where you left your keys? Looking for your sunglasses that are right on top of your head? If you regularly consume cannabis you might blame it on short term memory loss. How does marijuana affect your memory exactly? Is consuming cannabis really to blame for all the little things you forget?

Understanding Different Types of Memory

The first thing to understand is that there are more than a few types of memory. Memory is typically generalized into three different categories that include: sensory memory, short-term memory, and long-term memory.

Sensory memory is the ultra-short-term memory. Think like 1/5-1/2 a second. It’s the type of memory associated with the senses (touch, taste, smell, sound, sight). It can be attributed to something like glancing at a picture and then remembering what you saw.

Short-term memory (working memory) basically holds the information you are currently paying attention to or thinking about. Short-term memory lasts about 30 seconds. It’s believed that people can hold 7 (plus or minus 2) items in their short-term memory.

Long-term memory is when someone remembers something permanently. It can last a lifetime, and is comprised of memories of past incidents, facts, and how to do certain things.

The Way Marijuana Affects Different Types of Memory

Short-Term Memory

The most widely assumed aspect of marijuana and memory is its effects on short-term memory. Using marijuana will definitely impact your short-term memory. One study showed participants that smoked marijuana were slower and less accurate on short-term memory tests than participants that were given a placebo.

Other studies have shown that marijuana makes it difficult to form new memories after using it. It has also shown to make it difficult to recall events after consumption when a person is high, as well as after their high has worn off.

Marijuana doesn’t however, affect the overall function of a person’s short-term memory. And for those that smoke weed regularly, a reversal of its effects on short-term memory have actually been reversed. People who frequently use pot become less susceptible to these effects and don’t have problems with their short-term memory.

Spatial Memory

When people refer to marijuana messing with a person’s short-term memory, it’s really the spatial memory they’re referring to. One study conducted on zebrafish (who have strikingly similar brain and nervous systems to humans) found that giving these fish THC undoubtedly impaired their spatial memory.

Spatial memory is what gives you the ability to remember events in your immediate environment. Like where you left your lighter. Or your keys. Or your car.

Long-Term Memory

The effects of marijuana on long-term memory aren’t nearly (if at all) as significant as they are on spatial memory. Long-term memory is made up of two types of memory known as implicit and explicit memory. Implicit memory refers to things like unconscious muscle memory, while explicit memory refers to things like facts, memories, concepts, events, experiences, and places.

Most people who use marijuana have no trouble recalling events from their past. They can typically remember facts and concepts, and don’t forget experiences they had long ago. The use of marijuana isn’t believed to be a detriment to a person’s long-term memory in the slightest.


Marijuana does affect a person’s ability to recall certain things, however it’s just the spatial memory, the shortest of short-term memories. People don’t “blackout” on pot like they do with alcohol, however. They’ll definitely remember what happened the next day, even if they did have a few extra tokes and got too high. While they might forget where they left their keys, they’re bound to find where they parked their car.

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