Does Weed Permanently Damage Your Brain?

Estimated reading time: 30 minute(s)

As multiple US states have legalized marijuana use, its accessibility has become easier, making thousands of people use it without thinking much about the repercussions. The legalization has also led many people to believe that it is a potentially safe substance to use without any long-term or permanent side effects on the brain. However, experts have a reason to speculate that, like heavy use of heroin, meth, alcohol, and other similar substances, weed can also cause irreversible damage to the brain. This drug primarily affects the brain cells’ ability to deliver messages, leading to multiple concurrent symptoms inside the body.

If you or a loved one has been using this substance and is under the impression that it is safe with no long-term consequences, it is imperative to familiarize yourself with how does weed permanently damage your brain and how to minimize the risks.

Does Weed Permanently Damage Your Brain? Possible Side Effects

Marijuana’s side effects may not be comparable to those of alcohol, cocaine, and methamphetamine. However, the substance can still lead to undesirable cognitive impairments, some of which carry the potential to become permanent. These cognitive side effects may include the following:

It shrinks the brain

Multiple studies have confirmed that marijuana use in teenagers and young adults can cause brain changes. Some of these abnormalities have been directly linked to cognitive differences as well. Experts found that people who use marijuana heavily, such as five times during the past seven days or higher than 2500 times in their life, experience damage to the white matter in their brains. This part of the brain enables communication among neurons, and any damage to it causes higher impulsivity. These effects were found to be more prevalent in people who started using marijuana before the age of 16 years.

Brain shrinkage and other possible structural abnormalities are more likely to occur in people who started using early. Studies found that those who engaged in weed use before 16 make twice as many mistakes on executive functioning tests as those who started smoking marijuana later in life. These exacerbated results were attributed to the higher frequency of use in early smokers than those with a late onset. 

While most of the brain changes mentioned above have been found predominately in heavy users who smoke marijuana at least five times a week, occasional users also seem to be at risk. Additional studies that utilized MRI scans to detect brain changes in young populations who used marijuana at least once a week also found structural differences in the organ. Compared to non-users, their brains had changes in volume, shape, and grey matter density in two most important regions of the organ:

  • Nucleus Accumbens: This part of the brain plays a role in regulating pleasure, reward processing, and motivation
  • Amygdala: This part of the brain helps regulate emotions, memory, and decision-making.

The differences in the two regions mentioned above were more significant in people who smoked more marijuana.

It can lower the IQ

Research conducted on thousands of teenagers has revealed that those who use marijuana more than four times every week had a declined IQ by four points compared to non-users. So far, only a study of this nature has been performed, which proposed a link between weed use and intelligence loss. The results indicate the significance of frequency in determining the possible side effects of marijuana use.

It can slow down brain development in young populations

Studies comparing people who started smoking marijuana at early age versus those in later stages of life have not indicated any decrease in intelligence. However, these studies have proposed that because adolescents are still in the developmental stage with growing brains, their cognitive health is at a higher risk of impairment and stunting. Some experts also believe marijuana hinders brain development, putting users at risk of acquiring cognitive deficits. They also believe that the smaller the brain size of an individual who starts using marijuana, the more likely they are to experience a decrease in the size of a brain area called the prefrontal cortex.

It can alter the perception of reality

Having too little or too much dopamine in the brain can trigger mental illness. People who have been using marijuana for a long time generally have reduced dopamine activity which triggers psychotic symptoms similar to those found in schizophrenics. These symptoms primarily include hallucinations, paranoia, and anxiety. These symptoms are collectively known as cannabinoid-induced psychosis and can make it difficult for people to grasp the concept of reality. For such people, the brain’s processing speed also suffers, negatively impacting their cognition. Other studies have shown that marijuana users of young-age populations also experience slower processing speed, poor memory, low verbal learning, and low sequencing abilities.

It is important to remember that the problems mentioned above are not restricted to weed smokers only, but such people are at a much higher risk of experiencing them. The psychotic symptoms mentioned above approximately occur in 15% of the users and typically happen when a person is intoxicated. However, for some, these symptoms or the “bad high” associated with marijuana use may become permanent.

Effects of Cannabinoids on the Brain: Is the Age of Use Important?

As far as weed’s effect on the brain is concerned, these negative impacts can vary depending on the age of the person using it. Experts believe that marijuana appears to cause more harm to users under the age of 25 whose brains are still in the developing phases.


Studies investigating the effects of marijuana on the brains of adolescent users have reported several negative outcomes. Some of these research projects found that adolescents smoking week can lead to permanent deficits in memory and attention in addition to abnormal neural functioning and structural changes in the brain. Additionally, further investigations revealed that heavy weed use, spreading over 18 months, can decrease cognitive functioning and lower IQ levels. Early cannabis has also been associated with a heightened risk of acquiring mental health issues, such as schizophrenia and major depression. Experts also believe early use of this drug is a risk factor for acquiring addiction later on.


The effects of weed on neural structures and functions in adults are not so clear. Some studies do indicate that this substance can alter these functions and structures in adults, especially those engaged in long-term use. Further research has also revealed that adults using marijuana have a smaller hippocampus than people who do not use it. Moreover, the former also tend to perform worse on neuropsychological tests than non-users. Yet, plenty of other studies report no differences in brain volume and shape in people who use weed every day and those who do not use it at all.

Some experts have found that the cumulative exposure of adults to marijuana is linked to poor performance on memory and verbal tests. However, this cumulative exposure does not appear to affect executive function or processing speed.

Does Week Permanently Damage Your Brain: Seeking Treatment for Prevention

The studies so far have mixed opinions about whether using weed can cause permanent damage to the brain. However, the risk is always lingering unless we have more conclusive evidence and results, especially in chronic or heavy abusers. Unfortunately, weed addiction remains a very common problem in today’s world, and the problem has particularly worsened after the legalization of marijuana by various countries across the world. A large proportion of these cases remain undetected, and even if a diagnosis is made, very few people seek treatment for it. For instance, surveys suggest that over 5 million young adults between the ages of 18 to 25 years received a diagnosis of marijuana use disorder in 2021; however, only 28,000 of them sought treatment.

Unless treatment is sought, marijuana use can keep putting adolescents and adults at risk of damaging their brain structure and function permanently. Hence, connecting with a loved one or a professional is essential to start recovery as soon as possible. Accepting the struggle with marijuana use is not easy, and many people may worry about the potential implications of being open about their addiction issues, such as judgment from peers. All such people should remember that plenty of rehabilitation centers are working across the country to provide evidence-based help and treatment in a non-judgmental zone. If you believe that you or a loved one has been struggling with weed use and is at risk of permanent brain damage, do not hesitate to seek help to avoid regretting later.


What does THC do to the brain

THC is the primary active ingredient found in marijuana, and its use can cause multiple long- and short-term effects on the brain. The immediate effects may include the following:

  • Difficulty judging distances
  • Fatigue
  • Difficulty remembering
  • Confusion
  • Anxiety
  • Paranoia

Long-term use of marijuana, on the other hand, may cause the following side effects, some of which may become permanent:

  • A certain degree of cognitive impairment
  • Increased Marijuana tolerance
  • A certain degree of memory loss
  • Marijuana dependence

How severely does weed affect cognition?

The long-term use of any psychoactive substances, including weed, can cause potential neurological imbalances or impairments. However, the nature and extent of these cognitive impairments can vary depending on a few factors, which may include the following:

  • Age
  • Current physical health
  • The frequency of use
  • The strength of daily dosage
  • The duration of use

How do weed effects compare to alcohol and nicotine?

Wed, nicotine, and alcohol impact different neurological systems, triggering different types of long-term effects in the brain. One key difference that separates nicotine and alcohol from marijuana is that the former two are neurotoxic with the potential to kill brain cells. While some experts expect the same effects from marijuana use, it is still under investigation. At the same time, all three substances share some key similarities, such as their cognitive impairments being more pronounced in young users. Individuals who use marijuana, drink alcohol, or smoke cigarettes from a young age are likely to continue doing it later on in life. Long-term heavy use of all three substances can also lead to worse cognitive outcomes.

Does weed kill brain cells?

Despite the ongoing research querying the possible association between marijuana use and permanent brain damage, experts do not have any peer-reviewed concrete evidence that suggests the substance kills brain cells or alters their function or structure. In many instances, the research results have confirmed the opposite effect, with some of its cannabinoid chemicals possessing a neuroprotective effect. However, this does not completely exclude the risk of brain damage or mitigate the risks associated with smoking weed.  Like other substances, weed may have temporary effects on the brain cells, and some may die due to it. However, these cell deaths are unlikely to happen every time or in every user. Experts believe that almost all such risks of brain damage associated with weed are more likely to come from the act of smoking it. Smoking causes the combustion of weed to make it consumable while releasing several potentially toxic agents in the process, including tar and carbon monoxide. Inhalation of these compounds and exposing the body to hot smoke can reduce the oxygen levels in the blood and brain, making cell death more likely.

Get in Touch for Help