The Strange Things That THC Does To Memory

We’ve written before about what THC (the psychoactive compound in cannabis) does to REM sleep, and for the same reason that it’s prescribed as a PTSD treatment, it can be harmful to others (well, to people in general, but sometimes it may be considered worth it, if the benefits outweigh the harm). In short, it has to do with disrupting REM sleep and with it, disrupting memory:

Sweet Dreams Are Made of THC (Or Are They?)

This is, by the way, quite a different neurological process from that of alcohol-related blackouts: How Does Alcohol Cause Blackouts?

But, memory is not really just one thing, it’s many different kinds of things, that all get called “memory”. We talked about that a bit here: Is It Dementia? Spot The Signs (Because None Of Us Are Immune)

So what parts of memory does cannabis affect, and how?

You might want to jot this down

Researchers (Dr. Carrie Cuttler et al.) looked into what effects THC has on memory, acutely (i.e. the immediate effects), and for different kinds of memory.

What kinds of memory, you ask? They measured verbal, visuospatial, prospective, source, false, episodic content, and temporal-order memory to capture several different real-world memory functions.

In few words: participants who consumed THC performed significantly worse than the placebo group on most tasks, with impairments appearing in most of the 21 memory measures tested.

Not only that, but also, THC increased the likelihood that participants would “remember” words that were never presented in a list, sometimes inventing related words and sometimes unrelated ones.

This is interesting, because those in the THC-taking group also struggled to recall where information originally came from, which could make it harder to judge reliability—for example, distinguishing whether something was heard in a conversation or seen online.

Another thing that can affect real life a lot more than one’s ability to memorize data, is that participants who took THC were worse at remembering to carry out tasks later, a type of memory used for everyday activities such as taking medication or attending appointments.

There was one notable exception: episodic content memory—the ability to recall personally experienced events—did not seem to suffer statistically significant impairment in this study.

In the matter of dosage, might surprise you is that researchers found no meaningful difference between 20mg and 40mg of THC, meaning that even “moderate” doses can substantially disrupt memory systems.

Regular 10almonds readers may remember* talked about some related issues, here: How Much THC Is Safe?

^{*We hope you will remember, anyway!}

As for the research we’ve been discussing today, you can find it here: Mapping the acute effects of cannabis on multiple memory domains: A randomized, double-blind, placebo-controlled study

Want to learn more?

If you’d like to learn a lot more about the science of both memory and forgetting, then you might like this book we recommended a while back:

Remember – by Dr. Lisa Genova

Enjoy!