Can Marijuana Use Cause Brain Issues?

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One of the biggest problems with marijuana is that it has been highly politicized and the scientific facts surrounding it have been greatly misused by supporters and detractors in their narratives. This gives rise to misinformation that can do irreparable damage to a lot of lives since it can discourage people who need marijuana the most to not take it and also lead to the creation of laws that can limit access to it. 

One of the anti-marijuana camp’s strongest arguments is that “pot” causes irreparable brain damage especially in younger people. Yet ironically enough, one of the strongest cases in favor of marijuana is that of its amazing neurological benefits and that it may even hold the cure for some of the most sinister neurodegenerative disorders like Parkinson’s. This may sound ridiculously contradictory, but looking strictly at the scientific facts will allow us to clearly see how it is possible for this contentious plant to be both beneficial and detrimental to the brain. 

One man’s medicine is another man’s poison

The World Anti-Doping Agency has an absurd rule that lumps marijuana as a banned substance due to it being a performance enhancer and a health risk for athletes. Similarly, you’ll see all sorts of conflicting information online about the effects of cannabis on the neurological health of humans, with anti-drug websites highlighting only the negative effects. However, advocates are also guilty of downplaying the risks and ignoring the lack of scientific evidence, possibly in the eagerness to fight the system. Unfortunately, this does not help the regular Joe who is weighing the pros and cons of marijuana for his migraines. 

Does marijuana harm the brain?

Anti-drug websites, particularly the government’s, have no shortage of claims that show marijuana’s detrimental effects on the brain. But are these claims actually backed by studies and accurately written to inform? Let’s take a look at some of the most commonly cited brain problems caused by marijuana as claimed by the opposition and see if they are consistent with what the studies say:

  • It impacts the brain development of children – A few studies have found that youths, especially those who used heavily, showed structural brain abnormalities and altered neural activity. In particular, heavy pot smokers who began even before they were 16 were found to have less white matter which could be the cause of their observed impulsive behavior. 
  • It can permanently lower your IQ – There have been studies that suggest that cannabis use, especially at a younger age, can result in a lower IQ. However, there are also studies that showed that it doesn’t, even among teens. One thing that is clear though, is that other factors in the lives of the test subjects were more likely to be a bigger influence on the IQ scores than their marijuana use.  
  • It can increase the risk of psychiatric disorders – There are at least two studies that point to marijuana as an exacerbating factor for disorders like schizophrenia. However, the culprit seems to be THC rather than marijuana as a whole and even then, there are a lot of other factors in play, making it hard for researchers to establish with certainty the role of marijuana on the development of psychosis.
  • It increases “neural noise” – In a 2015 study, researchers found that ∆9-THC increased “neural noise” or random brain activity which is linked to psychosis experienced by schizophrenia patients and pot smokers.     
  • It can shrink the brain – While there had been a handful of earlier studies that suggested that even casual marijuana use can shrink parts of the brain used in learning, thus lowering IQ, some newer studies seem to directly contradict these findings. There’s also one study which showed that although heavy marijuana use may decrease brain matter, it may also increase connectivity between different parts. However, the results were not enough to confirm whether the changes in the brain were directly caused by marijuana use. 

Does cannabis use benefit the brain?

The benefits of marijuana are already well-recognized and this is the reason why medical marijuana is already legal in almost all states. However, studies that confirm its beneficial effects on the brain are few. Since most evidence neurological health are anecdotal, let’s look at the ones that are backed by studies:

  • It promotes neuroplasticity and neurogenesis – There have been a few related studies that show marijuana’s potential to induce neurogenesis and neuroplasticity. However, these tests are done mostly on rats and the results seem to show that while THC may induce neurogenesis, it only makes a positive impact on brains of older subjects and may impact young, developing brains negatively. Furthermore, CBD alone may hold greater promise in increasing brain cell growth. 
  • It helps with PTSD, anxiety and a number of other mental health issuesPTSD is already in the list of qualifying conditions for medical marijuana in most states. However, there’s not enough evidence at present to support the recommendation of marijuana for various mood disorders. Furthermore, it has been shown that THC may lower anxiety at lower doses but increase it at higher doses.
  • It increases the connectivity and structural integrity of the brain – In one study, researchers found that marijuana use also compensates for brain shrinkage by increasing connectivity and structural integrity. However, this sees a decline after six or eight years of chronic use.
  • It improves the behavior of patients with Alzheimer’s dementia – A few initial studies on rats have shown promising results, showing THC and CBD’s ability to attenuate brain inflammation, a biological hallmark of Alzheimer’s. THC in particular, was found to clear up tangled brain proteins and clogging plaques and may even hold promise in delaying the decline of aging brains. However, in humans, studies have only shown the effectiveness of marijuana (THC & CBD) in reducing agitation in Alzheimer’s patients, not in directly treating the disease itself.

Frequently Asked Questions on Marijuana’s Effects on the Brain

Does marijuana cause brain damage?

Studies suggests that while marijuana does not kill brain cells, chronic use does cause brain shrinkage but increases connectivity and structural integrity. However, it can negatively affect overall cognition and cause long-term impairment, especially for adolescent users.

Does marijuana cause mental disorders?

Marijuana, particularly THC, has been linked to an increased risk for psychosis and schizophrenia. However, the available data at present is not enough to confirm that cannabis can cause psychotic illnesses.

Can marijuana treat mental issues?

At present, marijuana is already used to treat PTSD and to some extent, anxiety and depression. However, data is lacking at present for researchers to conclude that marijuana will be effective in treating psychiatric disorders.

Can marijuana treat Alzheimer’s and Parkinson’s?

Marijuana has been shown to be effective in reducing agitation in Alzheimer’s patients and alleviate motor and non-motor symptoms in Parkinson’s but it still cannot be established that marijuana can treat both conditions directly.

Can marijuana lower your IQ?

While there had been studies that seem to point that adolescent marijuana use leads to lower IQ, this has been contradicted by subsequent studies which show that other factors in the user’s life may cause them to abuse marijuana and have lower IQ.


Based on the studies that are readily available, several things become apparent: THC is what makes marijuana potentially harmful to the brain, especially at a young age. However, at the right dosage, marijuana acts as a neuroprotectant and even promotes neurogenesis. While this may appear contradictory, this is only because of the lack of accurate information on how marijuana should be used for it to be a safe and effective form of treatment for neurological issues. Currently, recommendations on how to take marijuana for brain problems are based mostly on anecdotal evidence which leads people to self-medicate. This, coupled with the fact that there is a tendency for marijuana to be abused leads to mixed results among users, with some negatively impacted at a certain dose that produces favorable effects on others. 

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