Being high on weed really gets your mind going; sometimes thoughts can seem faster than the speed of light. In general, your body relaxes, your senses are more attuned, and your mind wanders. Though it seems blissful, these are all but temporary marijuana effects on brain function.

Hence it’s no wonder that people often say that after a good high comes a deeper low; the effects of marijuana can be quite intense and even entrancing. Sadly, they can also leave a lasting impairment.

A significant number of studies address the issue of health problems associated with the extensive use of cannabis. Prolonged exposure to high THC levels can make irreversible changes in the Central Nervous System (CNS); physiological and behavioral consequences usually follow suit as well. 

As society’s appetite for marijuana products continues to grow, one cannot stop but wonder — how does marijuana affect the brain?

To answer this particular question (and more), we reviewed both the health benefits of marijuana and its adverse effects.  

A Short Review of Cannabis Science

Marijuana Effects on Brain - Medical Background

The effects of marijuana have been enjoyed and admired for centuries, particularly its ability to soothe the senses. 

Seeing how it was officially marked as an illicit substance in the 20th century, marijuana scientific research was put on hold. However, its extensive recreational use revealed the immense healing potential of the herb. Today, the health benefits of marijuana are once again under the scientific scope. 

For two decades now, people have been looking for the answer to the question “what does weed do to your brain?” Well, let’s delve a bit deeper and find out!

The Endocannabinoid System 

Since their discovery in the early 90s, cannabinoid receptors have been popular in scientific circles. Today we know that they function primarily as maintenance channels for perpetuating the physiological equilibrium of the body (homeostasis). 

Also, it is safe to say that the endocannabinoid system acts as the chief regulating officer of the human body. Problems within this system can cause diseases, such as fibromyalgia, irritable bowel syndrome, migraines, or anxiety.

The relationship between marijuana and the brain is defined by the effects of the substance on cannabinoid receptors. According to research, there are two primary receptors in the endocannabinoid system — CB1 and CB2. They are highly prevalent in both the central and peripheral nervous systems.

CB1 is predominantly found in the CNS; brain imaging revealed their activity in the cerebral cortex, cerebellum, and brain stem. Nevertheless, their most profound activity concerns proper hippocampus function. CB1 influences motor coordination, the process of thinking, appetite, short term memory, pain perception, and brain immune cells.

CB2 is present throughout the body; it regulates the function of the cardiovascular system, the kidneys, the skin, bone tissue, fat tissue, the eyes, the lungs, the gut, and the pancreas.

How Does THC Affect the Brain?

The effects of marijuana are based on its main active chemicals — tetrahydrocannabinol (THC) and cannabidiol (CBD). They bind with cannabinoid receptors and engage in organ system control. 

When weed smoke is inhaled, it takes just a few minutes for THC to reach the brain and bind with said receptors. THC has a strong affinity for both CB1 and CB2; meaning, it influences the whole body. 

By attaching itself to the receptors, THC decreases the brain’s inhibitory neurotransmission. In other words, it enhances CNS excitation and creates new pathways that connect different brain structures.

How Long Do Cannabis Effects on the Brain Last?

The potency of a cannabis product depends mainly on the THC content within, which varies between different plant strains

Furthermore, depending on the dose inhaled, marijuana can reach its full physiological activity in approximately 30 minutes and the effects can last up to three hours. Its metabolites stay partially active within the system for two days. 

Still, marijuana side effects can last up to a week after just one use. 

A Remedy or a Narcotic?

Cannabis and its products are known to aid health conditions associated with inflammation, such as rheumatic diseases for instance. However, the effects of marijuana on brain development and performance make it hard to fully determine whether the benefits exceed the many adverse effects.

On the one hand, there is reliable data that confirms its therapeutic potential. On the other, the various marijuana side effects tell a different story altogether.

Neurological Benefits of Marijuana

Marijuana Effects on Brain - Benefits

The therapeutic use of cannabis for brain and nerve disorders is based on its proven neuroprotective properties, which are expressed by its anti-inflammatory and antioxidant effects.

Inflammation is a process that affects tissue caused by high levels of toxicity, physical damage, or underlying blood vessel pathology. It is usually followed by a series of harmful chemical reactions called oxidative stress. Inflammation and oxidation interfere with normal brain function and can cause the onset of new diseases.

What’s more, cannabis effects on brain tissue include the regulation of neurotransmission and the enhancement of overall brain connectivity. This is a direct effect of cannabinoid-receptor interaction; neuroprotection usually comes secondary, as a product of subsequent chemical reactions that follow receptor stimulation. 

The anti-inflammatory effects of marijuana have been thoroughly documented. Additionally, both THC and CBD have proven antioxidant properties. They help the body scavenge harmful free radicals and reduce hydroperoxide toxicity in neurons. They also decrease the effects of excitotoxicity in neurodegenerative diseases.

So, what does marijuana do to the brain that makes us want more? The ways it affects the brain and peripheral nerves are not just beneficial but can be used therapeutically as well. Today, there is a lot of scientific evidence that justifies the use of medical marijuana for brain and nerve disorders.

Pain Relief

Due to its analgesic properties, medical marijuana can be used for the treatment of mild chronic pain. However, in high doses, the adverse effects of THC can magnify the patient’s perception of pain. Therefore, it is recommended that no more than 10 mg of THC should be used for pain relief daily.

It is hypothesized that under the influence of marijuana, brain cells stop producing inflammatory signaling molecules, manifested as pain alleviation.

Muscle Spasms

Neuroprotective traits of marijuana can aid in various neurodegenerative disorders.

Cannabinoid receptors are present in nerve-muscle junctions. When stimulated by THC, they alter the nervous impulse and relax the muscles. Even in smaller doses, cannabis can alleviate certain neurological symptoms, such as tremors.

Early research on Parkinson’s disease shows that smoking medical marijuana can aid with stiffness. A study from 2004 revealed that 45.9% of Parkinson’s patients who took marijuana had a positive outcome regarding symptom relief.

Another useful marijuana effect on brain function — its neuro-regenerating effect. Although not yet confirmed, it is hypothesized that cannabis can influence brain cell regeneration, via CB1.

Spasm relaxing and regenerating properties are considered useful for treating Multiple Sclerosis.

Sleep Quality

According to a recent user survey, the consumption of medical marijuana promotes better sleep patterns and the feeling of restfulness.

Low doses of THC lower the blood pressure in the brain and stimulate CB1-regulated sleep onset. This is often followed by morning drowsiness. However, in chronic users, the accumulated effects of marijuana on the brain tend to downregulate receptor expression and stabilize the sleep cycle.

According to a study from 2019, 84% of people taking cannabis for sleep reported it as extremely helpful, while 87% of users described it as a useful substitute for sleep medication.

Epilepsy

The anti-seizure activity of cannabis is scientifically proven and quantified. Acting via CB1, THC destimulates both NMDA and GABA receptors in the brain, which are known to play a role in the onset of convulsions. Neuro-relaxing effects of weed on the brain are described as CB1-related inhibition of excitatory neurotransmission. 

Epidiolex is a cannabis-derived medication that is FDA-approved for the treatment of epilepsy.

Dementia

Alzheimer’s disease is associated with high levels of beta-amyloid protein accumulation in the brain. This is a metabolic consequence of excessive oxidative stress.

The benefits of marijuana use as a preventive measure have not been observed (yet). Nevertheless, the potential of cannabis to inhibit the toxic activity of harmful free radicals provides hope on its use as a dementia aid.

This antioxidative effect of marijuana on the brain can protect already altered brain cells from further oxidative degradation. In other words, cannabinoid compounds blunt the aggressiveness of chemicals that scavenge the damaged brain. In patients that use medical marijuana, this is observed mainly as the agitation decline.

Mental Health

There is evidence stating that marijuana can alleviate the symptoms of depression, anxiety, PTSD, and even psychosis. However, cannabinoids seem powerless to cause illness remission, therefore they can only be used as symptomatic aid. 

The connection between mental health disorders and cannabis use is complicated. This is because, under the influence of marijuana, brain structures react in a non-linear, intense way.

Studies that follow up on this often have mixed results. In some cases, people with underlying mental health conditions often use marijuana for symptom relief; they tend to fall to dependency, which worsens their condition.

In other cases, people with a medical history of an illness can use cannabis for symptom relief. Some studies reveal the healing properties of cannabis isolate on anxiety.

Negative Effects of Cannabis

Marijuana Effects on Brain - Downsides

According to new research adverse effects of marijuana on the brain can be considered within the aspects of structure, function, and connectivity.

The endocannabinoid system regulates the homeostasis in a physiologically balanced way. THC binds to cannabinoid receptors with great affinity, and overstimulates them, thus producing an overwhelming effect — what we call a “marijuana high.”

Short-Term Side Effects

Acute use is considered a solitary event, without repetition, and is usually followed by short-term side effects; if a person uses marijuana once a year, this is still considered repeated acute use. 

In this case, marijuana effects on brain performance are consequential to excessive cannabinoid stimulation. Therefore, short-term adverse effects are perceived on brain function and connectivity, while the brain structure remains intact. There is a low chance of lasting impairment in acute use, and the side effects are present until the “high” wears off. 

Neuroimaging studies have proven that when a substantial THC dose is taken, certain parts of the brain light up. 

Confusion

Weed increases brain blood flow, especially in the frontal region. Highly affected brain areas are the frontal, auditory, and visual cortex. Subjectively, this causes dissociation, depersonalization, and confusion. 

Connectional marijuana effects on the brain are expressed as an amplified synaptic activity. This creates a distorted perception of time while enhancing sound and color experiences. 

Altered Coordination

According to the evidence, THC increases functional connectivity in the sensorimotor cortex and reduces it in the prefrontal cortex. 

This means that marijuana alters movement patterns. In this case, short periods of muscle relaxation are usually broken with brief impulsive actions. Furthermore, by interfering with the brain-limb connections, weed slows down reflexes and impairs reaction judgment.

Attention Deficit

The THC-related functional changes in the parietal lobe, frontal lobe, and thalamus make it difficult to perform tasks that require focus. 

Marijuana effects on brain functions impair concentration and make it hard to follow a thinking pattern. In other words, weed-thinking is more likely to digress.

Impaired Memory and Learning

Marijuana affects the function of the hippocampus, therefore interfering with normal processes of learning and memory. Research claims that under the effects of THC, it can be challenging to form new quality memories and recall distant events.

Emotional Disturbance

THC affects the amygdala, a part of the brain that deals with emotions. Most of the data suggest that mood swings come as a result of induced anxiety. Marijuana effects on brain emotional processes are perceived as calm reactions but can be experienced in different ways. 

Depending on the THC-brain impact factor, weed can produce the feelings of both joy and fear.

Euphoria and Dysphoria

Cannabinoids affect the nucleus striatum — a part of the brain that secretes “happy” hormones, such as dopamine. This is how marijuana causes euphoria and a feeling of happiness. 

However, shortly after the effects wear off, the synapses run dry of dopamine — hence why the withdrawal symptoms usually include dysphoria and agitation.  

A Psychotic Episode

There is a dose-dependent mechanism in how marijuana affects the brain.

In low doses, healthy individuals can express mood changes, whereas psychotically-predisposed people mostly experience fear or severe disturbance.

However, high doses can precipitate an intense psychotic episode, followed by paranoia and hallucinations. In predisposed individuals, this can onset a chronic condition.

Negative Long-Term Effects of Weed

Marijuana Effects on Brain - Long Term

Chronic use is defined as the continuous use of marijuana — at least once a month — within a longer time frame. Heavy users take pot chronically, for at least six days a week, and are more likely to develop consequences.

Long-term effects of marijuana on the brain cause structural changes. High THC levels overstimulate the cannabinoid receptors, which influences their decrease in number. Over time, this disrupts brain functionality, forcing the brain to adapt.

Due to excessive THC levels, the brain tends to change its connection patterns to maintain homeostasis regulation. Meaning, the brain creates new pathways. A study from 2019 confirmed this by proving that heavy cannabis users, i.e. those experiencing cannabis dependence, tend to have lower white matter integrity and higher grey matter thickness in the cortex. 

This does not mean that marijuana kills brain cells. Namely, it just alters them. What’s more, these brain changes can create lasting side effects.

Memory Decline

Research on heavy users states that memory and learning can be impaired after more than a week of successive use. There is also evidence for memory changes reversing in cases with longer abstinence, whereas others persist.

Behavioral Changes

Prolonged use of cannabis can create an antisocial personality, with frequent relationship problems. In this case, under the influence of marijuana, brain damage causes psychological consequences; behavioral changes to one’s personality can lead to long-term irritability, nervousness, and social agitation.

Demotivational Syndrome

This is one of the most frequent marijuana side effects. It is described as the low spiritual sense of self, diminished self-image, and no admiration for personal success. It can persist for years (during abstinence) and cause certain behavioral problems, such as melancholy. 

Demotivational syndrome is a consequence of dopamine depletion in the brain, altered connectivity in the prefrontal cortex, and impaired amygdala function. If severe, it can lead to depression.

Mental Health Problems

Does marijuana cause brain damage and mental issues, or is it just a myth? Well, long-term use can lead to psychiatric conditions. The severity depends on the frequency of use, as well as the THC-potency of the marijuana product.

Depression

In otherwise healthy users, depression usually lasts until the complete recovery of the endocannabinoid system. In previously depressed people, abstinence usually requires psychiatric interventions.

Anxiety

According to evidence, the most common form is social anxiety during the abstinence phase. In predisposed people, it can result in panic attacks or generalized anxiety.

Psychosis

It has been documented that in genetically predisposed people, during prolonged exposure to marijuana, brain cell alterations include subsequent inhibitions of some parts of the brain. This can lead to manic behaviors, often associated with paranoia and delusions.

Addiction

According to official sources, about 9% of marijuana users become addicted. 

Heavy pot smokers quickly develop tolerance, a state of receptor desensitization. Tolerant users need larger doses in order to get “high.” This leads to frequent repetition and overuse. 

Overuse creates both psychological and physiological reactions that lead to dependence. Marijuana dependency is described as the presence of severe withdrawal side effects. 

Only a portion of dependent people become addicted. Marijuana addiction is referred to as the uncontrolled need for it, regardless of the consequences, and it is treated clinically.

Effects of Marijuana on Teenage Brain Functions

Marijuana Effects on Brain - Teenagers

Most of the long-term side effects in adults can reverse, compensate, or change in time.

However, research states that marijuana permanently changes the brains of young heavy consumers.

In adolescence, the brain is in its peak of developmental plasticity. Several psychological traits form in this period of life, such as learning, motivation, identity, and habit formation. Marijuana use can put all of that at risk.

In contrast to non-smokers, teenage marijuana users experience changes in shape, volume, and grey matter density. According to neuroimaging, they have distinct structural alterations in the hippocampus and amygdala. This can diminish their planning, abstract thinking, executive functioning, learning, and pleasure processing capabilities.

Marijuana effects on brain development include severe psychosocial changes that can inhibit both basic functioning, and the ability to grow intellectually.

Another study determined that chronic users who began using marijuana before the age of 18, had a significant IQ drop at the age of 38. The ones who started smoking pot after the age of 18 exhibited no significant changes. 

Additional research claims that 17% of adolescent users develop marijuana addiction.

Pregnancy and Marijuana

Available data shows that cannabis exposure during pregnancy affects fetal brain development.

The mechanisms behind this are uncertain. However, marijuana effects on the brain manifest in increased tremors and poorer habituation to visual stimuli of the child.

Pharmacological studies in preclinical trials found that THC rapidly crosses the placenta. Although fetal exposure is lower than maternal, this points to significant developmental changes. 

Some researchers concluded that prenatal exposure to marijuana has an impact on the child’s development later on. Observed ten-year-olds with positive prenatal exposure had difficulties with learning, memorizing, and displayed certain behavioral changes, such as impulsivity, as well.

FAQs

Does marijuana kill brain cells?

Compulsive marijuana use can lead to structural and functional brain changes. THC binds to human cannabinoid receptors with high affinity, and if the exposure persists, it leads to lasting changes in the nervous system. 

Although brain cell death is not perceived, there is evidence that reveals brain-altering traits of THC.

What is THC?

Tetrahydrocannabinol (THC) is the most potent chemical component of cannabis plants. It binds to human cannabinoid receptors and expresses strong physiological effects, such as the lowering of blood pressure and an increased heart rate. It has psychoactive properties and can lead to addiction.

What does marijuana do to your brain?

By acting on cannabinoid receptors, marijuana alters brain function and connectivity. Certain functions can be impaired, such as learning, memory, sensing, and emotional experiences. Additionally, marijuana induces the release of dopamine, which causes euphoria, which can lead to withdrawal syndromes.

Is marijuana a depressant?

Marijuana cannot be defined as a depressant as it actually inhibits the depression neurotransmitters. In the brain, it causes excitation and alters the connections between different brain parts. 

Nevertheless, marijuana relaxes the muscles and lowers the heart rate and can be considered as a systemic relaxant as such.

Conclusion

It is tough to describe the performance of the brain on marijuana. The majority of weed experiences tell a story of extreme pleasantness and even transcendence. Subjectively, it can be relaxing and insightful.

Neurological effects of marijuana are well documented and show promise in the treatment of neurodegenerative disorders, epilepsy, and pain conditions. 

However, THC is a robust brain-effective agent, which increases brain blood flow and alters connectivity between different brain structures. The use of marijuana often results in confusion, impaired coordination, attention deficits, and mood changes.

Heavy users are at risk of acquiring lasting conditions as marijuana effects on brain structure in compulsive users go to show, including cognitive impairment, lasting behavioral changes, chronic lack of motivation, or severe mental health problems.

To sum up, it very much depends on the way you are consuming/using marijuana and the CBD/THC ratio, as well as how often you enjoy the cannabis plant.