does weed kill brain cells


The question: Does weed kill brain cells has been one that has been asked for many years. Although smoking marijuana does seem to make the user think and move slower, we still do not know for sure if using weed kills brain cells.

Despite the fact that more research needs to be done to determine the difference between the effects of smoking vs. vaping, or ingesting edibles, marijuana has still become legalized in many parts of the U.S.

The studies that are evaluating the cognitive effects of long-term marijuana use are ongoing. Here is what we currently know about how weed affects the brain.

How Does Weed Kill Brain Cells?

Rather than eating edibles or vaping it, does smoking weed kill brain cells? Well, it is not understood explicitly if marijuana kills brain cells or even if it affects IQ. The obvious main result of using marijuana is the fact that it slows you down. Despite this, a few studies were completed to dig deeper into this question.

Does Weed Kill Brain Cells? – The Studies


In a well-known 2012 study from New Zealand, 1,000 individuals were monitored for over 38 years. The researchers who performed this study reported an association between ongoing marijuana use and cognitive decline. Specifically, it was found that:

  • People who started heavy marijuana use as young people, and continued as adults, lost an average of six to eight IQ points by the time they reached their midlife.
  • Those who stopped using marijuana as adults did not regain these lost IQ points even after discontinuing use.
  • People who started using marijuana as adults did not experience IQ loss.

This study had a considerable impact on thoughts regarding marijuana use.

These results suggest that marijuana use as an adolescent may have consequences on the adult brain that are irreversible. Despite this, there were also a few limitations to this study. Mainly, it is not possible to understand if it was the marijuana causing brain cells to be decreased or if it was because of another variable.


In a 2013 reply study, it suggested that personality factors affected both marijuana use as well as the cognitive decline found.


A study from 2016 found that genetic factors can also contribute to cognitive decline, which means that the original 2012 study may not actually answer whether or not marijuana kills brain cells.

In a different, longer-term study of 25 years, also published in 2016, marijuana use and cognitive function were assessed in 3,385 participants. The study found that users of marijuana performed worse on tests of verbal memory and processing speed. It was also found that continuous exposure to marijuana resulted in poor performance on verbal memory tests.

Despite this, continued exposure didn’t appear to affect the speed or general function of these individuals.

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Conclusion of These Studies

The main takeaway from these studies is that more research needs to be done over long periods of time to truly understand the long-term effects of marijuana.

Does the Age of Use Effect if Marijuana Kills Brain Cells?

After reviewing many studies, it is apparent that marijuana use before the age of 25 might affect brains still developing.


Multiple studies have been done examining the effects of marijuana on adolescent user’s brains. In a few studies, it has been found that adolescent marijuana use is associated with potentially permanent attention and memory deficits. It has also been related to structural brain changes and abnormal neural functioning.

In general, heavy marijuana use seemed to have an association with decreases in IQ and cognitive functioning. Adolescent marijuana use is also has been found to trigger specific mental health disorders, and increase substance abuse problems.


The effect of marijuana use on the brain is much less clear amongst adults. Although it has been found that long-term marijuana use may alter brain structure, it is not proven.

Across 14 studies done in 2013, marijuana users were found to have a smaller hippocampus than non-users. The hippocampus is an area of the brain associated with memory. This study eventually concluded that chronic, long-term marijuana use might be specifically related to cell death in the hippocampus.

The problem with answering the question “does weed kill brain cells,” is that some studies have found heavy marijuana users performing poorly on neuropsychological function tests, but then others report no significant differences.

Effects of Marijuana

Short-Term Effects

  • Confusion
  • Fatigue
  • Poor memory
  • Poor concentration
  • Inability to learn
  • The decrease in motivation for some
  • Poor coordination
  • Trouble making decisions
  • Poor depth perception
  • Anxiety
  • Panic or paranoia

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Long-Term Effects

Continuous studies are being done on the long-term effects of marijuana on the brain. For now, the main long-term risk of using marijuana is regarding other substances. Marijuana has been known to put addicts at risk of relapsing on other drugs or to be used to soothe the negative effects of “come down” in more intense drugs such as cocaine.

Immediate Placement in Marijuana Rehab

Medicinal Effects

Marijuana is legal in 16 states (plus Washington D.C) and is legal for medicinal purposes in 27 others. This is due to some of the positive effects it has shown for a variety of ailments such as:

  • Chronic pain relief
  • Regulation of diabetes
  • Links to fighting cancer
  • Seizure regulation
  • Relieves symptoms of ADHD and ADD
  • Treats glaucoma
  • Slows down the development of Alzheimer’s
  • Helps with PTSD symptoms

Is Marijuana Addictive?

Marijuana use can lead to the development of problem use, known as a marijuana use disorder. It is not to be said that all weed smokers develop an addiction, but around 30% of those who use marijuana may develop some use disorder with the drug.

People who stop using marijuana frequently can report irritability, mood and sleep difficulties, decreased appetite, cravings, restlessness, and other discomforts for the first two weeks. The reason marijuana dependence occurs is due to the brain adapting to heavy usage by reducing the production of its endocannabinoid neurotransmitters.

How Does Weed Compare to Alcohol or Nicotine?

Alcohol, nicotine, and marijuana all affect different neurological systems; and have different long-term effects on the brain. One main key difference is that alcohol and nicotine are both neurotoxins. This means that they are proven to kill brain cells, however, we cannot determine if marijuana kills brain cells over time yet.

There is one similarity; all three substances have larger cognitive effects on young people. It is also proven that frequent and long-term use of alcohol, tobacco, or marijuana are all associated with negative cognitive outcomes.

What is Weed’s Relation to Mental Illness?

Cannabis use early on in life is associated with an increased risk of mental health conditions such as depression, major depressive disorder (MDD), and schizophrenia. For example, is the use of marijuana causing and triggering psychotic episodes, hallucinations, or delusions?

Although studies have reported a low dose of delta-9-tetrahydrocannabinol (THC) restored age-related cognitive deficits in mice, more studies need to be done to find out the long-term effects of marijuana usage.

Takeaways: Does Weed Kill Brain Cells?

  • We cannot truly conclude that marijuana use kills brain cells.
  • Pre-existing differences can make some people more likely to use weed more than others.
  • One conclusion is that those who were younger at the age of first use, those who used frequently, and those who used in high doses, are associated with poorer cognitive outcomes.
  • There are minimal studies that have truly investigated the differences between the effects of smoking, vaping, or ingesting marijuana.

Marijuana Addiction Treatment at Resurgence

Does weed kill your brain cells? It should not matter if it does or not because the main issue with marijuana use is its addiction role. If you are struggling with a marijuana use disorder or are using marijuana in conjunction with a different addiction, it is vital to get help. Contact Resurgence Behavioral Health to get help with your addiction today.

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