Cannabis Science

Does weed kill brain cells?

does weed kills brain cells

Did you know the average adult human has around 100 billion cells? We already know that marijuana affects the brain by interacting with the endocannabinoid receptors. Some substances, like cocaine, have been proven to kill brain cells. But does weed kill brain cells?  Which category does weed fall in? Let’s see what science says.

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Does weed kill brain cells?

There are mixed answers to this question. Firstly, according to Healthline, more research is needed to determine whether or not weed can kill brain cells. Medical News Today also echoed the same sentiment that the answer is currently unknown. However, some studies say otherwise.

Marijuana doesn’t cause permanent damage, according to study

A 2003 WebMD article cited a study that concluded that daily marijuana use or heavy use, in general, doesn’t cause permanent damage. 

Lead researcher and psychiatrist Igor Grant, MD. was quoted on WebMD saying, “We were somewhat surprised by our finding, especially since there’s been a controversy for some years on whether long-term cannabis use causes brain damage.”

The researchers found a minute impairment in learning and memory in people who used weed. However, after analyzing 15 studies before that one, the article says, “scores on thinking tests were similar to those who don’t smoke marijuana.”

How does weed affect the brain?

Weed affects the brain in a number of ways. When you smoke weed, tetrahydrocannabinol (THC), binds to receptors in the brain known as endocannabinoid receptors. The main ones are CB1 and CB2. CB1 receptors are predominately found in the central nervous system while CB2 receptors are found predominantly in the peripheral nervous system. 

To provide some context, according to Healthline, the endocannabinoid system is said to be responsible for sleep, appetite, memory, reproduction, and fertility as well as mood. 

Chemically, THC is pretty similar to anandamide. Therefore, according to National Institute on Drug Abuse, “Similarity in structure allows drugs to be recognized by the body and to alter normal brain communication.”

When cannabinoids bind to the receptors you may have various experiences. For example, when THC binds to the endocannabinoid receptor you may feel high. You can also thank a similar interaction for getting the munchies or sleeping better. 

Effects of Weed on the Brain

We can separate the effects of weed on the brain into long-term and short-term effects. 

Short term effects of weed on the brain

Weed has short-term effects on the brain and according to Healthline, some of them are:

  • impaired concentration
  • confusion
  • impaired learning
  • difficulty making decisions
  • impaired coordination
  • difficulty judging distances
  • increased reaction time
  • impaired memory
  • anxiety, panic, or paranoia

In some cases, there could be delusions, hallucinations and psychosis. 

A study on short term effects of marijuana on the brain

A study called, Short-term effects of marijuana smoking on cognitive behavior in experienced male users, tested the participants in nine different ways on their ability to use abstract concepts. Some of the tests included a letter series test, Luchin’s Hidden Word Test and closure speed test. The study concluded that there were some impairments for some of the tests. It said, “Marijuana smoking led to a dose-related impairment on the letter series, word grouping, closure speed, and Embedded Figures test.” However, in addition to that, “Performance on the size-weight illusion, Luchin’s Water Jar, Luchin’s Hidden Word, and the anagram tests were unaffected.” Finally, “conceptual clustering decreased after marijuana smoking.” Conceptual clustering was a memory test. 

Weed and your IQ

According to a 38-year long study, people who use weed heavily as adolescents lost 6-8 points by the time they reach middle age. The study found that even if those teenagers quit as adults they didn’t regain their IQ points. Interestingly, people who started using weed heavily as adults didn’t lose their IQ points. Healthline noted that one of the limitations of this study is that there could be other reasons for these results outside of weed, such as genetic. 

Long term effects of weed on the brain

There may be some long-term effects of weed on the brain. According to Healthline, the following may be long term effects of weed use:

  • Memory problems
  • Issues with concentration
  • IQ
  • Problems with decision making
  • Problem-solving issues
  • Increased risk of substance abuse disorders

A study on long term effects of weed on the brain 

A study titled Long-term effects of frequent cannabis use on working memory and attention: an fMRI study didn’t find any long-term effect on working memory and attention. The study says, “No evidence was found for long-term deficits in working memory and selective attention in frequent cannabis users after 1 week of abstinence.” However, the researchers also concluded that frequent cannabis use could still affect brain function. The study says, “frequent cannabis use may affect brain function, as indicated by altered neurophysiological dynamics in the left superior parietal cortex during working memory processing.”

How weed affects adolescent brain structure

It has been said that when people use weed in adolescents it may have some negative consequences for them.  Some research has shown that weed may actually affect brain structure. In contrast, other studies say adolescent cannabis use is not associated with structural brain differences in adulthood.

One study found that adolescents who used weed had a decrease in the right medial orbital prefrontal cortex volume in comparison to their counterparts who don’t use weed. Other studies found problems with weed user’s white matter or the hippocampus. 


So to answer the question “does weed kill brain cells”, we don’t know. There needs to be way more research in this area. What we do know is that marijuana does affect the brain both long-term and short-term for some people. In addition to that, there seems to be a change in brain structure due to weed, especially for those who start using weed earlier in life. While weed provides many people with great benefits, we still need as much research as possible on potential negative effects. That way, we can then research how to mitigate them so people can enjoy the benefits more and worry less about any negative consequences.


About Trevann

Trevann is Stoner Rotation’s Jamaica-based lead writer for the Science section of our cannabis blog. She graduated with honors receiving her Bachelor of Science degree in Molecular Biology from the University of West Indies, Mona. For the last three years, she has covered some of the biggest questions around cannabis and health underpinned with research from supporting studies, medical journals and scholarly articles. Got something on your mind? You can reach her at [email protected].