Updated on February 6, 2024
3 min read

Does Weed Kill Brain Cells?

Does Weed Actually Kill Brain Cells?

Many states are legalizing marijuana. Some health critics are wondering, does marijuana kill brain cells?

It’s a common misconception that weed takes a toll on the human brain, killing cells, but this is not necessarily true.

Some studies evaluate the cognitive effects of marijuana use for chronic cannabis users, but more research needs to be done on whether or not consuming marijuana can actually kill your brain cells.

Some studies link marijuana to cognitive decline, particularly in adolescents. Other studies show positive correlations between marijuana use in older adults and cognitive functioning. This article discusses these studies in detail. 

Ways Weed Affects the Brain

Weed can affect the brain in a few ways. The Cannabinoid type 1 and CB1 receptors are connected to the brain’s nerves that play a role in memory, mood, pain regulation, and appetite.

That’s why you might have trouble remembering if you smoke weed or eat a THC-infused edible. Weed can also cause mood swings or increased hunger. 

You might also develop a higher tolerance to pain after smoking weed or consuming THC-infused products.

What Neurotransmitter Does Weed Affect?

Consuming marijuana affects neurotransmitters in the brain. That’s because marijuana’s primary psychoactive ingredient is tetrahydrocannabinol (THC).6 

THC is one of the 113 cannabinoids recognized in cannabis. It attaches to the brain’s Cannabinoid receptors type 1 and CB1.

Short-Term Effects of Marijuana Use

Weed affects different people in different ways. There are many short-term side effects of marijuana use. Not everyone will experience these side effects.

  • Fatigue
  • Increased appetite
  • Apathy
  • Difficulty judging distances
  • Trouble with memory 
  • Confusion
  • Paranoia
  • Anxiety

The short-term side effects of marijuana depend on factors like the type of marijuana you use and whether or not you’ve consumed other substances, like alcohol and other drugs.

Long-Term Effects of Marijuana Use

The long-term effects of frequent marijuana use depend on how much marijuana someone consumes over a period. 

One study suggests that using marijuana as an adolescent has an irreversible effect on brain development. More research supports this, indicating that marijuana takes a bigger toll on people under the age of 25.2 

Some researchers have found that marijuana use in adolescence is tied to changes in the brain’s structure.3

A 25-year longitudinal study that assessed marijuana use and cognitive function found that marijuana users perform worse on verbal memory and processing speed tests.1

Can Weed Affect Your IQ?

One 2012 study from New Zealand found that persistent cannabis use is correlated to cognitive decline (over 38 years).4

The study discovered that people who heavily used marijuana from adolescence into adulthood lost an average of six to eight IQ points by middle age. The same couldn’t be said for those who started using marijuana as adults.4

However, the study had its fair share of limitations. The researchers couldn’t conclude that weed was the sole source of cognitive decline.


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Will My Memory Improve After Quitting Weed?

The New Zealand study shows that quitting weed did not help those who lost IQ points recover them.4 But another study says that quitting can help improve your memory.5

The study suggests that just one month of cannabis abstinence can improve working memory in adolescents and young adults. The biggest improvement happens in the first week.5

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How Long Does It Take the Brain to Recover from Weed?

How long it takes for your brain to recover from consuming too much marijuana depends on a variety of factors:

  • How long you’ve been consuming marijuana
  • How much marijuana you consume
  • The type of marijuana you consume
  • How old you were when you started consuming marijuana
  • If you are taking other drugs while consuming marijuana

Quitting marijuana can have obvious short-term effects. But marijuana’s long-term effects can be potentially permanent.


Studies are inconclusive about whether or not weed kills brain cells.

Many researchers believe that weed does take a toll on those who start heavily consuming weed in adolescence.6 But more research purports the positive effects that weed can have on adults.

More research needs to be done to fully understand the effects of marijuana on the brain of persistent cannabis users.

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Updated on February 6, 2024
6 sources cited
Updated on February 6, 2024
  1. Auer, Reto, et al. “Association between Lifetime Marijuana Use and Cognitive Function in Middle Age: The Coronary Artery Risk Development in Young Adults (Cardia) Study.” JAMA Internal Medicine, U.S. National Library of Medicine. 
  2. Is Cannabis Safe to Use? Facts for Young Adults Aged 18–25 Years.” Government of Canada.
  3. Jacobus, Joanna, and Susan F Tapert. “Effects of Cannabis on the Adolescent Brain.” Current Pharmaceutical Design, U.S. National Library of Medicine.
  4. Persistent Cannabis Users Show Neuropsychological Decline.” PNAS.
  5. Stopping Marijuana Use Improves Memory.” National Institutes of Health, U.S. Department of Health and Human Services, 2021.
  6. Weir, Kirsten. “Marijuana and the Developing Brain.” Monitor on Psychology, American Psychological Association, 2015.

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