There’s no shortage of solid evidence that proves alcohol destroys brain cells (1). Anti-marijuana activists say that marijuana has the same effect, but let’s think for a second. If this is true, then how come alcohol is completely legal while marijuana is still illegal in many parts of the United States? If they both destroy your brain cells, why is one completely legit while weed continues to be either heavily regulated or completely criminal? How come marijuana-related products such as CBD oil continue to change lives every day? Does weed kill brain cells? What is the connection between weed and brain cells?

“Marijuana Kills Brain Cells” Myth

I guess you can tell where I stand on this issue just by looking at the subheading above. The idea that weed kills brain cells originated in the 1970s and 1980s. The pseudoscience making the rounds at that time, however, traced a lot of their origins from the fake research conclusions popularized in the 1930s.

The 1970s was a crucial time in terms of American marijuana policy because this was the beginning of America’s war on drugs (2). As anybody with more than two brain cells can tell, the war was a very expensive failure. It ended up with a lot of people going to jail, and the drug “problem” remaining uncontrolled and unabated.

Since that time, anti-marijuana activists kept repeating the idea that weed irreparably harms the human brain. While marijuana does produce effects that are very noticeable in the short-term, when compared to alcohol or other drugs, it doesn’t have the same negative long-term effects. Unfortunately, websites like the Drug-Free World continue to spread the lie that weed destroys brain cells (3).

Judging content from that site, you might think that smoking weed will turn you into some sort of brain-dead zombie unable to climb stairs, let alone become president of one of the world’s most powerful countries. These types of sites alternate among fake science, blatant lies, and intentionally biased interpretations of otherwise legit scientific studies. This is why we have made it our mission to spread accurate and reliable information about marijuana on Quitnet.

We also wanted to let you know about CBD. If you didn’t know already, CBD products (such as CBD oils) allow you to enjoy the medicinal benefits of marijuana without the head high, bloodshot eyes or lazy “stoner” sensation.

Millions of people around the world are starting to realize just how effective CBD is compared to smoking weed. We tested various companies in the last few months and found cbdMD to be of an exceptionally high quality – so we suggest taking a look if you are interested.

Let’s go back to the topic of smoking marijuana.

I would be lying to you if I were to claim that cannabis has absolutely no negative effects. However, a little bit of perspective would go a long way. The anti-marijuana lobby seems hell-bent on distorting and exaggerating whatever negative effects marijuana has in their bids to control public opinion. It appears that they don’t even bother checking their facts or doing a deep-level analysis before repeating the same tired conclusions about weed.

New Zealand IQ Test Report

It doesn’t matter which website you read. All supporters of the “pot destroy brain cells” theory will cite a 2012 New Zealand study. This study monitored over one thousand participants and compared the scores of their IQ tests from the age of 13 to their scores when they reach the age of 38.

All 1036 study participants were closely tracked from birth all the way to age 38. The formal name for this research is the Dunedin Study (4).

Interviewed at several intervals (at the ages of 18, 21, 26, 32 and concluding at the age of 38), test participants were asked about how much weed they smoked. The Dunedin study showed that the IQ score of people who smoked weed showed an average drop of eight points.

Of course, this finding was music to the ears of anti-marijuana advocates all over the world. They would say that this is all the proof anybody would need, but if you actually bother to read the report and dig through the numbers, a different picture appears.

When you look at the study, it actually had serious design mistakes. Given these mistakes, no self-respecting statistician or scientist would rely on this study as an objective and accurate report on how marijuana affects the human brain.

For instance, the highly reported IQ drop among test participants only occurred among people who were chronic smokers. These people had become physically dependent on cannabis before they reached 18 years of age.

Given the huge size of the sample, it is worth noting that only thirty-eight subjects exhibited a great drop in their IQ score. Also, it’s worth remembering that these are people who would smoke weed at a minimum of four days every single week over a twenty-year period! If you don’t know what the effects of smoking weed every day are, click here.

Moreover, the study does not explore the influence of socioeconomic differences among test participants. If properly accounted for, this class disparity might partially explain the drop in IQs. Put simply, were these people high school dropouts? Did they suffer from a very difficult childhood?

Unfortunately, the people who designed the Dunedin study didn’t even explore these very relevant factors (5). We will never know how much of an impact all these other important factors played in the study’s results.

In another study released in December 2015, identical twins were monitored over a decade. Twins who smoked weed suffered a four-point IQ drop. Interesting enough, the non-pot users also showed a similar drop (6).

The more plausible explanation for the comparable drops in IQ is probably related to environmental factors like peer influence, school life, and family problems.

Marijuana & Brain Cells

Research indicates that marijuana’s negative effects on the human brain are temporary. For example, cannabis can get in the way of your memory and learning processes for a brief period.

In a Harvard University 2001 study, researchers analyzed the cognitive performance of study participants both when they smoked weed and after they stopped (7). The participants took a range of attention, memory, learning and intelligence tests during the time they stopped using weed.

The study conclusively showed that people who smoked a lot of weed had far lower memory test scores in the week immediately after they quit. Interestingly enough, their memory test scores dramatically improved and became normal a month after they quit. This shows conclusively that weed’s mental effects are not permanent.

In the past two decades, quite a number of research studies have shown that pot users don’t have to worry about their IQ scores dropping.

In a 2003 study, researchers reviewed fifteen existing studies that focused on the long-term effects of marijuana on the brain. This cross-study analysis showed that pot smokers did not suffer serious impairment as far as their memory and learning go (8).

In fact, the impairment effect was labeled “minor”. Igor Grant, the lead researcher of this cross-study, said he was shocked at the results (9). He said that he expected a very big difference between people who are heavy pot smokers compared to casual users. The difference between the two groups was, in his words, “very minimal”.

Similarly, in a study produced by the University of Colorado Boulder involving weed users’ scans didn’t show any physical changes in key areas of their brain compared to non-weed smokers (10).

Disadvantages Of Smoking Weed

Although the studies we’ve described above all show that weed is not going to significantly change adult brains, the same cannot be said when it comes to adolescent users.

Please understand that at the adolescence stage of brain development, the brain has not yet fully matured. This means that excessive teenage weed smoking is not a very good idea. Although the verdict is still out regarding marijuana’s long-term effects on juvenile brains, it doesn’t make much sense to consume marijuana if your brain hasn’t fully developed. This can lead to potential harm later on. You might just be exposing yourself to unnecessary risk.

For this reason, we fully agree with current regulations in the few states that have gone ahead and decriminalized marijuana that weed should be restricted to adults. You only need to look at the Dunedin study to see the wisdom of this. The people who experienced significant drops in IQ scores were the ones who started smoking pot when they were teenagers.

It’s also important to note that smoking anything can have a negative effect on your brain. It doesn’t matter whether you’re smoking tobacco or marijuana. When you smoke, there’s a chance that certain parts of your brain will not get the oxygen it needs. Your brain is actually the most oxygen-dependent organ in your whole body (11).

Any period of oxygen deprivation can lead to cellular damage. Accordingly, if you are worried about this, you might want to ingest weed through edibles (cookies and other baked goods or pastries) or even consider buying CBD oils.

Can Weed Enhance Your Brain?

If you’re a big Kool-Aid drinker when it comes to the claimed negative effects of marijuana, you might want to skip this section. It might just shatter your existing biases. Believe it or not, there is quite a bit of evidence that suggests smoking pot can actually boost brain processes!

Weed’s beneficial effects center on neurotoxins like aspartame and fluoride. These chemical compounds can cause your nerve cells to malfunction. Your nerves may not be able to convey the information they carry at peak efficiency and effectiveness.

There are certain compounds found in cannabis which helps protect the brain from neurotoxin damage. These compounds also called cannabinoids have also been shown to be chemical antioxidants. They help shield your brain cells from damage.

In a study released in 2015, CBD was shown to reduce the levels of a neurotoxin that’s been linked to the onset of Parkinson’s disease. This neurotoxin has been shown to act as some sort of trigger to a nervous breakdown (12).

Additional research suggests that THC (the active mind-altering compound in marijuana) can cut down on the buildup of amyloid plaque and reduce inflammation in the brain. These two processes often work hand in hand to produce Alzheimer’s disease (13).

Finally, this same study showed that pot compounds may help promote the regeneration of brain cells by reducing the effect of neurotoxins.


In addition to being a flat-out myth, the idea that marijuana destroys brain cells has been shown by several studies to run contrary to reality. In certain situations, it turns out cannabis actually helps your brain function better.

While we should be very careful regarding adolescent marijuana use, several dozen studies have concluded that smoking weed does not damage the brain over the long-term. You don’t have to worry about your ability to pick up new information or remember stuff. Whatever negative effects marijuana has are strictly short-term.

Sadly, marijuana is still the boogeyman of America’s drug warriors and too many public policy analysts. It is really quite a shame the more weed is demonized, the more people turn a blind eye to alcohol’s extremely negative health effects.

It has conclusively been proven that alcohol has a massively negative long-term effect on the human brain. For example, a 2017 research report by Thayer showed that long-term alcohol use is linked to reduced volumes of gray matter and degraded the integrity of the brain’s white matter (14). Scary stuff. Your brain actually shrinks due to chronic long-term alcohol use much like a cucumber shrinking during the pickling process (15). This same effect has not been detected in marijuana users. Good luck getting this information from the mainstream media though.

Unfortunately, we’re at a point where regardless of how much hard data researchers come up with showing that weed doesn’t really kill brain cells, the anti-marijuana lobby is all too eager to twist any and all information they come across just to support their agenda. You only need to look at the Dunedin study for a prime example of this.

What makes this all so frustrating is the mainstream media’s eager participation in the ongoing demonization of weed. After all, the media gets higher ratings when they sensationalize or play up the ‘evils’ of cannabis. This has always been the case since the “Reefer Madness” of the 1930s and we don’t expect the media’s slant to change anytime soon (16).

Next time someone asks you “does marijuana kill brain cells?” – you can now respond with your very own detailed explanation.