How Does Marijuana Affect Your Memory?

People who smoke pot have a reputation for being forgetful or absentminded. But what's the real science behind this?

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Episode Transcript

Speaker 1 (00:00):
Hey, this is Julie Douglas from the podcast The Stuff
of Life here to tell you that super producer Noel
Brown and I are cooking up season two for an
August release. So if you haven't already checked out season
one of the Stuff of Life, there's a big bowl
of ten episodes ready for you to dig into on
iTunes or wherever you get your delicious podcast take out from.

(00:21):
In the meantime, apply sunscreened liberally and we'll see you
in August. Welcome to brain Stuff from How Stuff Works. Hey,
brain Stuff, this is Christian Seger. So here in the
United States, marijuana is most commonly used as an illicit drug.

(00:46):
Our society thinks of stereotypical users as being you know,
forgetful and absent minded. And this is because the main
psychoactive ingredient in marijuana impairs our memory. It's called tetro
hydro cannabinal or for the sake of you know, brevity,
th HC. Th HC alters how information is processed in

(01:06):
the hippocampus. This is the area of the brain that
is responsible for memory formation. However, you consume marijuana, THHC
enters your brain by latching onto a protein called cannabinoid
receptor type one, or c B one for short. There
are c B one sprinkled throughout the brain. There in
your cortex, basil, ganglia, the hypothalamus, and the hippocampus where

(01:30):
we form our memories. See where I'm going here for
a short term memory. Forty years worth of different studies
show that th HC disrupts our short term memory, making
it hard to form new memories when you're high. This
also makes it really difficult to remember what happened when
you were high, even after the th HC wears off,
and larger doses of th HC have even more of

(01:53):
an effect on memory. Frequent users are more tolerant to
the th HC, however, and its effects including memory loss.
But what about recalling your existing memories. Th HC does
not actually affect that, nor does it lead to memory
loss or dementia. Therefore, users can remember things they already know,
like their name or where they live. And Our bodies

(02:16):
have a biological system made of natural marijuana like compounds.
This is called the endocannabinoid system. It regulates our memory formation,
functioning as a filter so we're not overloaded with information.
The system is involved in the extinction of our negative
memories as well. That's what they call it extinction. It
can influence pain, memory, mood, and even appetite, and researchers

(02:40):
hope that by using THHC they can help people forget
bad memories such as post traumatic stress disorder. So studies
do show that as people age, they lose neurons in
the hippocampus, and chronic THC use can hasten this loss. Also,
a study out of Northwestern University published in March of

(03:00):
fifteen showed that teens who smoked daily for three or
more years have been found to have an abnormally shaped hippocampus.
They also performed poorly on long term memory tests, eighteen
percent worse than those who didn't use marijuana. The deformation
of the hippocampus is thought to be connected to this

(03:20):
poor memory. Subjects in this study took a narrative memory
test where they listened to a series of stories for
one minute twenty to thirty minutes later, they were asked
to recall as much from the stories as they could,
and this assessed their ability to encode, store, and recall
details from their stories. The longer the individuals used marijuana chronically,

(03:41):
the more abnormal their hippocampus was shaped. This probably damages
its neurons and its axons, as well as supportive environments.
The abnormalities didn't seem to go away either, even when
observed in individuals in their early twenties who had stopped
using marijuana for over two years now. It's important to

(04:02):
note that drawing definitive conclusions about marijuana's long term effects
is difficult because steady participants often use multiple substances. Rats
exposed to th HC before they're born, after birth, and
during rat adolescence show problems with learning and memory tasks
later in their lives. A rats hippocampus changes as well

(04:25):
when it's exposed to th HC, and imaging in human
adolescence shows that regular users display impaired neural connectivity. This
affects memory, learning, and impulse control. The endocannabinoid system is
important to the formation of our synapses during early brain
development and refining them during adolescence, so it's possible that

(04:49):
marijuana use is affecting this development. If you want to
learn more about marijuana, memory, and medical health, I recommend
that you go check out my other podcasts stuff to
blow your mind. We just recently did two deep dive
episodes into marijuana. Check it out. Check out the brain

(05:11):
Stuff channel on YouTube, and for more on this and
thousands of other topics, visit how stuff works dot com