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How exactly does marijuana damage brain cells?

How exactly does marijuana damage brain cells?



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I've heard that THC can cause permanent damage to brain cells. I've also heard this reffered to anti drug propaganda. Another theory i've read is that temporary effects reduce intelligence but long term results are not affected. If Marijuana does cause permanent brain damage how does it do so? How exactly does it kill the cell?


There is no damage of brain cells, as in the context of lesions in neurodegenerative disorders. There are, however, two mechanisms attributed to the memory loss associated with cannabis/marijuana and these are purely physiological responses.

  1. Astrocyte mediated: CB1R (cannabinoid receptor) in astrocyte gets activated and promotes glutamate release. This glutamate induces Long Term Depression in post synaptic neuron. Synaptic currents can cause both LTP and LTD. The properties of the synaptic current wave dictates the outcome. Please refer to review articles on LTP and LTD for more information.
  2. GABAergic interneuron mediated: CB1R activation in GABAergic interneurons (inhibitory neurons) causes activation of mTOR pathway and promotes protein synthesis. CB1R activates mTOR through PI3K/Akt.

How Marijuana Affects Your Body

Let’s be honest: This is why most people use marijuana. THC is what causes the high. When you smoke marijuana, THC goes from your lungs to your bloodstream and then makes its way to your brain. There it connects to parts of certain cells called receptors. That’s what gives you those pleasant feelings. You can also get marijuana in things like cookies and brownies. These are called edibles. They get into your blood through your digestive system.


Marijuana affects each person differently depending on their biology, the plant’s potency, previous experience with drugs, the way a person uses the drug, and the use of alcohol or other drugs at the same time. Some people feel nothing at all when they use marijuana. Some feel relaxed or high. Others suddenly get anxious and paranoid this happens especially when a person uses stronger marijuana, takes too much, or isn't used to taking it. We're still learning about how marijuana affects the brain and how long the effects will last—especially after someone stops using the drug.

Regular marijuana use has also been linked to memory and relationship problems, poorer mental and physical health, lower salaries, and less career success. 6

Short-term effects (while using or right after using)

  • learning, attention, and memory problems
  • distorted perception (sights, sounds, time, touch)
  • poor coordination
  • increased heart rate
  • anxiety, paranoia
  • psychosis (not common)

Effects that last longer than the short term (a few days) but may not be permanent

Long-term effects (effects of repeated use)

  • risk of marijuana addiction
  • long-term learning and memory problems if heavy use begins during youth
  • risk for chronic cough, bronchitis
  • risk of schizophrenia in some people with higher genetic risk
  • in rare cases, risk of recurrent episodes of severe nausea and vomiting


Does cannabis kill brain cells?

Whether cannabis, or marijuana, kills brain cells remains unknown, and current research studies have yielded conflicting results.

Keep reading to learn more about what current studies have to say about marijuana’s short- and long-term effects on the brain.

Share on Pinterest Marijuana may affect a person’s appetite, pain regulation, and mood.

Please note that the studies covered in this article mainly consider the effects of tetrahydrocannabinol (THC) on the brain. THC is the psychoactive compound in marijuana, or cannabis, that creates the ‘high’ effect. THC is just one of over 100 cannabinoids found in marijuana.

The body naturally produces endocannabinoids, which are similar to cannabinoids. Both cannabinoids, such as THC, and these natural endocannabinoids, bind to the same receptors in the brain.

Researchers have identified two types of these receptors:

  • CB1 receptors located in the central nervous system
  • CB2 receptors, which develop in the peripheral nervous system

When endocannabinoids bind to CB1 and CB2 receptors, they affect the following body functions:

  • appetite and metabolism
  • pain regulation
  • learning
  • memory
  • mood
  • cardiovascular functions
  • reproductive functions
  • immune system functions
  • muscle and bone formation
  • coordination and motor control
  • reward and addiction behaviors

Cannabinoids, such as THC, and naturally occurring endocannabinoids may have significant effects on brain function and development. This is because regions of the brain that control memory, learning, motor control, and sensory perception contain high concentrations of CB1 receptors .

Current research on this topic has yielded conflicting results. Some studies suggest that THC has potentially permanent neurotoxic effects that impair people’s verbal learning, memory, and focus. Other studies indicate the opposite.

In one 2017 animal study , researchers compared differences in working memory between adult rats exposed to a synthetic cannabinoid and those exposed to glucose during adolescence.

The researchers found that the rats they exposed to cannabinoids had a significantly better working memory in adulthood than the control rats.

In another 2018 animal study , researchers found that exposure to THC induced brain tissue growth and improved learning and memory function in rats.

In a 2016 study , researchers assessed the cognitive function of 3,385 people aged 18–30 by looking at the data from the 25-year-long Coronary Artery Risk Development in Young Adults (CARDIA) Study that began in 1986. At year 25, 84% of these participants reported previous marijuana use, but only 9% reported using marijuana into middle age.

After adjusting for demographic factors, psychiatric conditions, and other drug use, the researchers found long-term exposure to marijuana was associated with impaired verbal memory.

However, they found no evidence to suggest an association between marijuana use and cognitive processing or executive function.


What Cannabis Actually Does to Your Brain and Body

Cannabis is the most popular illicit(ish) drug in the world, and it’s gaining in popularity as the push for legalization—medicinally or recreationally— spreads to more and more states . But what actually happens in your body when you partake? Let’s take a look at this fascinating drug, its health effects, and potential concerns about using it.

Cannabis is a controlled substance. lacking in controlled, scientific research

Before we start, we should note that a whole lot more research needs to be done in this area. Although cannabis has been used for centuries as a medicine and as an inebriant (it’s even mentioned in the Old Testament several times as “kaneh-bosem”), we don’t know a great deal about the health effects of using it. That’s because there haven’t been many controlled studies on it, largely due to the way cannabis is classified by the federal government.

The Food and Drug Administration classifies cannabis as a Schedule I drug , with “no currently accepted medical use and a high potential for abuse.” (Fun fact: heroin, ecstasy, and LSD are also Schedule I drugs, but cocaine and meth are considered less dangerous Schedule II drugs.) There are two exceptions: FDA-approved drugs made from cannabidiol (CBD) with “no more than 0.1 percent tetrahydrocannabinols” are on schedule V, the same list as codeine-containing cough syrups. And hemp—defined as cannabis plants that contain less than 0.3% THC—is unscheduled thanks to the 2018 Farm Bill .

Because garden-variety cannabis is still on Schedule I, you need a license from the DEA to study it, and your study must be approved by the FDA. To obtain research-grade cannabis, you have to go through the National Institute on Drug Abuse, Popular Science explains . Otherwise, since it’s federally illegal to have cannabis (even in states that have legalized it), researchers working in hospitals, colleges, or other institutions that receive federal funding risk losing their funds to do this research.

There have long been movements to reclassify cannabis and open up the doors for more studies, but, for now, here’s what we do know about cannabis and our health.

What cannabis does to our brains in the first couple of hours

Cannabis contains at least 60 types of cannabinoids , chemical compounds that act on receptors throughout our brain. THC, or Tetrahydrocannabinol, is the chemical responsible for most of cannabis’s effects, including the euphoric high. THC resembles another cannabinoid naturally produced in our brains, anandamide, which regulates our mood, sleep, memory, and appetite.

Essentially, cannabinoids’ effect on our brains is to keep our neurons firing, magnifying our thoughts and perception and keeping us fixed on them (until another thought takes us on a different tangent). That’s why when you’re high, it’s really not a good time to drive, study for a test, or play sports that require coordination, like tennis or baseball. Like alcohol , caffeine , and sugar , cannabinoids also affect the levels of dopamine in our brains, often resulting in a sense of relaxation and euphoria.

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Salon explains a few more ways cannabis interacts with our brains, such as impairing our ability to form new memories, and how cannabinoids cause the classic “munchies.”

The effects will depend on the amount taken, as well as how potent the preparation is (common cannabis contains 2 to 5% THC, while ganja can contain up to 15% THC and hashish oil between 15 and 60% THC). At high doses—and if you don’t follow our advice on edible safety —cannabis can produce scary curled-up-on-the-couch-for-hours hallucinatory states.

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As with other drugs, cannabis’s effects will also vary by individual. Not all people may find taking it an enjoyable or relaxing experience for those who have anxiety or are prone to panic attacks, cannabis could exacerbate their symptoms rather than bring on a sense of calm.

Cannabis may have long-term effects on memory and concentration

The short-term effects of cannabis are generally felt within a few minutes, peak within 30 minutes, and wear off after about two or three hours. The bigger question is: What happens if we use marijuana more regularly, or are occasional but heavy users? Are there permanent cognitive and other health changes? Do we all risk turning into The Dude from the Big Lebowski?

Again, we don’t have many rigorous scientific studies on this, much less many longitudinal studies. A 2012 review of available research published in the Journal of Addiction Medicine found that the immediate impairments on memory and concentration aren’t likely permanent. But a 2018 review by Colorado’s public health department concluded that daily users of cannabis can have impaired memory lasting more than a week after quitting. Whether memory or other cognitive problems may last longer than that is still unclear.

Colorado’s Department of Public Health & Environment offers a list of statements about the health effects of using cannabis, and a detailed list of how strong the evidence is for each statement . Evidence for most of the mental health effects is “limited” or “mixed,” but a few findings have substantial evidence behind them. They include:

  • Adolescents and young adults who use cannabis are more likely to develop psychotic symptoms and disorders like schizophrenia.
  • Heavy use of smoked cannabis is associated with chronic lung problems like bronchitis.
  • People who use cannabis can become addicted to it over time.

Compared to other drugs, cannabis is less addictive and less harmful

Addiction is a very complex topic . It’s possible for people to get addicted to anything that gives us pleasure. While cannabis addiction is real, it is a rarer addiction than other (legal or illegal) substances. Statistics say that 9% of people (roughly one out of 10) who use cannabis become dependent on it, compared to 32% of tobacco users, 20% of cocaine users, and 15% of alcohol drinkers.

When it comes to cannabis and other substances, some say what matters most might not be how addictive the substance is but how harmful it might be. Former Surgeon General Jocelyn Elders told CNN she supports legalizing cannabis, saying it “is not addictive, not physically addictive anyway.” Time reports :

As Dr. Elders also said on CNN, marijuana is nontoxic. You can fatally overdose on alcohol, heroin or cocaine, but the only way a dose of marijuana will kill you is if someone crushes you under a bale of it.

Although evidence shows that it’s possible to develop a substance use disorder, and withdrawal symptoms after stopping heavy use, cannabis has still been shown to be much less dangerous and addictive than other substances—over 100 times safer than alcohol—but that’s not to say it is completely harmless. How cannabis is consumed and prepared can make a big difference on its health effects, for better or worse, as well.

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Cannabis is more dangerous for teens

The chances of getting addicted to cannabis increase if you’re a daily user or if you start when you’re a teen. According to the National Institute on Drug Abuse, cannabis addiction goes up to about 17% in those who start using young (in their teens) and to 25 to 50% among daily users.

Dr. Damon Raskin , internist and Diplomat of the American Board of Addiction Medicine, advises:

Marijuana these days can cause changes in the brain that impair learning, especially in teenagers as their brains have not finished developing. Brains are not fully developed until the age of 25 or 26. Chronic marijuana use can lead to changes in both personality, judgment, and reasoning skills.

Pot damages the heart and lungs, increases the incidence of anxiety, depression and schizophrenia, and it can trigger acute psychotic episodes. Many adults appear to be able to use marijuana with relatively little harm, but the same cannot be said of adolescents, who are about twice as likely as adults to become addicted to marijuana.

Much of the marijuana available today is more potent than it was in the past, so the potential exists for it to have more intense deleterious effects on the user. Medical professionals are seeing more emergency room visits with excessive vomiting, and with adolescents, there is greater risk of psychosis and delirium.

If you’re a parent, this is another reminder to talk to your kids about drugs , especially during those formative years.

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Smoking is riskier than other methods of using

Cannabis is most commonly smoked, but it can be used in vaporizers, turned into a tea, or used as an ingredient in foods as an edible. Oils and tinctures are often made from the cannabis plant as well for medicinal purposes. Of the many ways to use cannabis, smoking seems to have the most harmful side effects. According to the American Lung Association :

Smoke is harmful to lung health. Whether from burning wood, tobacco or marijuana, toxins and carcinogens are released from the combustion of materials. Smoke from marijuana combustion has been shown to contain many of the same toxins, irritants and carcinogens as tobacco smoke.

Beyond just what’s in the smoke alone, marijuana is typically smoked differently than tobacco. Marijuana smokers tend to inhale more deeply and hold their breath longer than cigarette smokers, which leads to a greater exposure per breath to tar.

Secondhand marijuana smoke contains many of the same toxins and carcinogens found in directly inhaled marijuana smoke, in similar amounts if not more.

A review of studies in 2013 , however, found mixed evidence linking heavy, long-term cannabis use to pulmonary disease or lung cancer and concluded that there’s definitely a bigger risk for these if you smoke tobacco.

Still, regular users might consider other options besides smoking, such as vaping and edibles. Ata Gonzalez, CEO of G FarmaLabs , says:

Traditional methods (joints, blunts, etc), first off, aren’t the most efficient and certainly aren’t the cleanest ways to do it. These paper-based methods can be harsh on throat and lung tissue over time, potentially introduce the possibility of inhaling mold spores, and can be carcinogenic depending on what the cannabis is rolled in. Vaporizers are a much better option if you’re going to smoke it, not only because it’s much more discreet, but it introduces cannabinoids into the bloodstream as a gas through heat, rather than as smoke due to combustion. Vaping also reduces any possible exposure to harmful toxins/byproducts because the marijuana is never burned.

Conversely, there’s always the edibles option. This method is the most efficient way to get cannabinoids into the system because it’s done through the gastrointestinal tracts instead of the lungs – this also means that absorption is slower and the effects seem like they’re delayed, but that’s because the body has to process THC through the liver. The resulting effect, however, is a much more body-focused “high” that’s optimal for pain relief. Tinctures and tonics are sometimes classified in this subset/consumption category. Finally, we have topical solutions made with cannabis oil (e.g. salves, lotions, ointments, etc.) which are best used as anti-inflammatories and analgesics.

Additionally, if you partake, you’ll want to know where your cannabis came from—who grew it, how they grew it, how they harvested it, and so on. (You can even buy Willie Nelson’s own brand of weed from his stores!) If you don’t know, however, consider Global Healing Center editor Ben Nettleton’s suggestion to water cure your stuff:

Water curing is basically just soaking your stuff in water and changing the water several times. The water draws out any water soluble impurities. So any leftover fertilizer, pesticides, fungus (recent Smithsonian touched on the prevalence of that), and even innocuous unnecessary compounds like salts and chlorophyll. Pretty much just like giving it a wash. THC is not water soluble so you don’t lose any of what you want.

We tend to think of cannabis as a hippy all-natural movement, but today legal cannabis is the fastest growing industry in the US—a multi-billion dollar industry —and the purity and quality of the cannabis can matter a great deal to your health and its effect on you.

There are many possible medical uses for cannabis

Finally, there are the potential medical uses of cannabis for a wide variety of conditions. 33 U.S.2 states and DC have legalized the medical use of cannabis to treat symptoms of cancer, AIDS, arthritis, multiple sclerosis, migraines, epilepsy, nausea, and other conditions. 76% of doctors surveyed said they would prescribe cannabis for medicinal purposes. And Procon.org’s analysis of 60 peer-reviewed studies on medical marijuana found 68% of them concluded treatments were positive for the conditions treated.

As with the adverse effects of cannabis, however, the research here is still limited and lacking. CNN’s Dr. Sanjay Gupta , who changed his stance on cannabis and now questions cannabis’s categorization as a Schedule I drug, says that of the recent papers on it, the overwhelming majority—about 94%—are designed to investigate the harm while only 6% investigate the benefits of medical cannabis.

So what we’re left with is anecdotal evidence. Greta Carter , cannabis activist, entrepreneur, and founder of a chain of clinics tells Lifehacker:

What we know is that the VA has clearly identified the benefits of marijuana on post-traumatic stress syndrome. We also know that parents who have struggled daily with children suffering from seizures and movement disorders go to extremes to relocate their families to states that will allow them access to the medicine. We’ve heard from patients with AIDS and Cancer who find benefits from cannabis. There are studies outside of the US that actually show tumors being reduced with cannabis treatment. I find it unconscionable that we as a country that have over 500 deaths a year to aspirin, and none to cannabis in its entire history would ever try to stand in the way of this plant being readily available to whomever might seek it.

With those being the extreme situations advocating for cannabis, I am more of the position that cannabis is a part of overall wellness for many. … Having served over 1,000 patients a month (40K to date) walking through my clinics and the average age growing older each year, the stories I’m more accustomed to hearing go like this: The aging population who come in and report that they take over 14 kinds of medications (and some of them are meds to offset the side effects of the other meds), in a year after incorporating cannabis, they come back and are down to 2 or 3 meds and enjoying a better quality of life. From those who have suffered from addiction to pain pills, they use cannabis to manage their pain and are off of their pain meds. The stories going on and on.

Opponents of medical cannabis argue that it’s too dangerous to use (though the arguments seem to be mostly associated with the effects of smoking rather than cannabis in general or cannabis administered in other ways), that cannabis is addictive, and that legal drugs make cannabis unnecessary.

Health professionals and researchers (and lawmakers) on both sides of the debate continue to argue the pros and cons of cannabis use. As for us regular people, 58% of respondents to a poll conducted by the progressive think tank Data for Progress said they were in favor of cannabis (recreational or medical) being sold legally, just like alcohol is.

As ever, “further research is recommended” (isn’t that how all studies conclude?) In the case of cannabis, though, we really do need to know more.

This story was originally published in March 2015 and was updated on Nov. 3, 2020 with current information and links.


The Chemistry of Cannabinoids and the Human Body

A little over a month ago, I wrote about the discovery of the endocannabinoid system – which is arguably one of the most important endogenous systems known to man. There is so much going on inside our bodies that we are only now starting to understand – and that is all thanks to curiosities raised about the marijuana plant.

Now that we’ve got a background on how the endocannabinoid system was found, I think it’s time to take a good look at how it works. With an understanding of the endocannabinoid system comes an understanding of exactly how and why marijuana affects us the way it does and why it can be therapeutic is so many different situations.

The Anatomy of the Endocannabinoid System

In most biological systems – such as the nervous system – our brain sends our body messages via chemicals called neurotransmitters, which are released from a neuron, called the presynaptic cell. They travel across a tiny gap called the synapsis and from there attach to specific receptors on a nearby neuron, called the postsynaptic cell.

This is how our body controls just about everything from how we think to what we do – this is the process that keeps my fingers moving across the keyboard as I type this. The reason it’s important to understand this is so you can understand why the endocannabinoid system eluded scientists for so long – it works in reverse .

Rather than passing along messages from the presynaptic cells, cannabinoids are created on-demand by the postsynaptic cell. The cannabinoid then travels in reverse, to the presynaptic cell, where it attaches to a CB2 or CB2 receptor.

Since cannabinoids are responsible for things such as sleep, metabolism and appetite, among other things , this is important to understand. Once the cannabinoids attach to the presynaptic cells they can control what happens when the next messages are sent out.

The CB receptors can be found throughout the entire body – CB1 receptors are generally found in the nervous system, connective tissues, gonads, glands and organs CB2 receptors are most often found in the immune system and its associated structures – and in some tissues you will find both. There may be a third cannabinoid receptor that has still yet to be found.

Naturally, if our bodies are outfitted with a system specifically designed for cannabinoids, it’s unlikely that we don’t already produce some ourselves. The cannabinoids produced by our bodies are known as endogenous cannabinoids – or endocannabinoids. The most common endocannabinoids and most well understood are anandamide and 2-arachidonolyglycerol, or 2-AG.

The other naturally occurring cannabinoids are called phytocannabinoids, which are cannabinoids that come from plant matter. The cannabis sativa plant is known to have over 500 natural compounds – of which at least 85 have been identified as cannabinoids.

Of these cannabinoids, the most well-known are THC (tetrahydrocannabinol) and CBD (cannabidiol). THC is the psychoactive compound that offers the “high” that is associated with marijuana use. CBD, on the other hand, is non-psychoactive and actually counteracts the effects of THC.

Other less understood cannabinoids occurring in the cannabis plant include CBN (Cannabinol) and CBG (Cannabigerol). CBN is created through a process called oxidization, when THC is exposed to the air, and it is mildly psychoactive. CBG is non-psychoactive and has been shown to reduce intraocular pressure – explaining why marijuana works so well for glaucoma patients.

There are also synthetic cannabinoids – created in part to help discover the endocannabinoid system and its capabilities. These synthetic cannabinoids were created to replicate THC and, as I mentioned in the last article, they are actually FDA approved for treatment of severe nausea and wasting syndrome. (Yet the naturally occurring cannabinoid remains illegal at a federal level…)

How the Endocannabinoid System is Responsible for Homeostasis

The effects of endocannabinoids are more local and much shorter lived than that of cannabinoids from cannabis, due to the fact that they are broken down quicker. All cannabinoids and the endocannabinoid system itself are accepted to be the system behind regulating homeostasis.

Homeostasis, to keep it simple, is the body’s ability to maintain a stable internal environment, regardless of external changes. Basically, without the endocannabinoid system, our bodies would have no means of keeping all the other biological systems in check.

For example – tumor cells are shown to have more cannabinoid receptors – when certain cannabinoids attach to the receptors in a cancerous cell it then continues to cause the cell to consume itself – therefore promoting homeostasis by destruction of the cell.

Another great example of the endocannabinoid system at work would be at the site of an injury – cannabinoids would be decreasing the release of activators and sensitizers of the injured tissue which would stabilize the nerve to prevent an excessive response as well as calming immune cells all of which aim to minimize pain and damage from the injury,

Alongside promoting homeostasis cannabinoids also play a large part in our social environment as well. Cannabinoids are responsible for behavior – as expressed in the way the psychoactive cannabinoid THC affects things such as humor and creativity. This poses the theory that the endocannabinoid system one direct link between body and mind and the doorway to understanding our consciousness.

How THC and CBD Reacts to the Endocannabinoid System to Provide Relief

Speaking of how THC affects the mind (and the body as well), the endocannabinoid system is the answer to that question. While scientists may not have a full understanding of the system at work, there has been years’ worth of research on how THC reacts within the body (remember, that lead to the discovery of endocannabinoids in the first place!).

When THC is introduced to the body it seeks out those cannabinoid receptors throughout the body. The THC aims to find the CB1 and CB2 receptors, and when it attaches to those receptors the effects vary depending on the potency of the plant being consumed.

CB1 receptors are the ones that control things such as sleep, appetite, mood and even the sensation of pain. When THC is introduced, these receptors alter the messages sent from presynaptic neuron to postsynaptic neuron – enhancing the effects. This is why insomniacs and rheumatoid arthritis patients can find relief through high-THC strains of marijuana.

The CB2 receptors are the ones that regulate the immune system, so when THC attaches it starts an anti-inflammatory response. It has also been shown to aid in the reduction of cancerous cells. This is likely why diseases such as Crohn’s Disease and HIV are successfully treated with marijuana.

The large number of THC cannabinoids attaching to the thousands of CB1 and CB2 receptors are altering the messages sent to our brains, therefore minimizing symptoms that make us uncomfortable and promoting homeostasis.

CBD works much in the same way as THC – it attaches to the CB1 and CB2 receptors, however the CBD cannabinoid seems to work towards healing and working as a natural anti-inflammatory. This is likely why it makes such a large impact on patients who are suffering from conditions such as epilepsy.

Alone these cannabinoids can work wonders in healing the sick, by allowing our body’s access to additional cannabinoids to promote homeostasis. If for some reason our body cannot produce the right amount of natural cannabinoids or other chemicals, introducing external phytocannabinoids can stimulate the receptors in the same way, promoting the same functions.

However, when we introduce whole plant cannabis, whether smoked or vaporized, the numerous cannabinoids that enter your system will all be working towards the common goal of internal balance – reducing pain, anxiety, depression, nausea and more.

Understanding the endocannabinoid system and how cannabis reacts to it can help anyone to use cannabis in a healthy way – whether it be to treat a chronic condition like R.A. or something treatable like cancer or even something as simple as a broken bone or a migraine.

The science proves it – our bodies are designed to use cannabinoids to maintain normal function and homeostasis – that alone should be enough to prove marijuana can work successfully as a medicine, don’t you think?

04/28/2016 Update:

A quick note after having this issue being brought to my attention: It is still debated whether or not CBD actually hits the CB1 and CB2 receptors in the same way that THC does . However, there is evidence that they do have a minimal affinity for the receptors, which could be what allows the anti-inflammatory effects often associated with its use. It may even be that it is binding to a different part of the receptor than THC would , which could explain why the two seem to work best when paired together.


Now let’s see what happens once you smoke…

Marijuana enthusiasts know that being under the influence will change your perception of self and the world around you. So even though regular users might not think it’s too bad of an idea to jump behind the wheel stoned or possibly light up on the road, this 2013 study published in the open-access journal PLOS One suggests that THC changes your perception and attention so much that it can be difficult or dangerous to drive.

The study shows the levels of brain activity in people who are performing a “visuo-motor tracking task” that simulates the cognitive processing and visual recognition a person would use to drive.

There are a lot of studies that show the inner workings of the brain of a person who uses marijuana, but there aren’t too many that actually show what it looks like while they’re stoned.

In this case, people who smoked marijuana and attempted the exercise showed a decrease in blood flow to their anterior insula, dorsomedial thalamus, and striatum compared to people who smoked placebo weed.

Now if you recall, the insula is associated with initiating actions based on physical state, and the striatum is associated with reward and decision-making. The dorsomedial thalamus is involved with memory and cognition.

The authors of this study say the decreased activity in these three brain regions suggests that stoned people have issues with saliency detection, which is a fancy term for being able to determine whether what you’re looking at is important. This, along with decreased activity in the dorsolateral prefrontal cortex (an area that, if you remember, lights up before you even smoke and is involved with making decisions based on risk calculations), means that people who are under the influence of marijuana have trouble figuring out what they’re looking at and doing something about it.

While high, you might not realize that your dog is eating your Fritos, or, more dangerously, maybe not react in time to see a pedestrian running in front of your car.

The pattern of brain activation associated with smoking marijuana, in a general sense, suggests that smokers are more interested in their internal world than the external world.

“Subjects are more attracted by intrapersonal stimuli (‘self’) and fail to attend to task performance, leading to an insufficient allocation of task-oriented resources and to sub-optimal performance,” write the researchers. Fascinatingly, some of this brain activity seems to start before a person has even taken the first puff.


Protein structure reveals how LSD affects the brain

Lysergic acid diethylamide, or LSD, can alter perception (awareness of surrounding objects and conditions), thoughts, and feelings. It can also cause hallucinations—sensations and images that seem real even though they’re not. These “trips” can last many hours, long after LSD has been cleared from the bloodstream.

LSD was first synthesized in 1938, and its hallucinogenic effects discovered soon afterward. However, how the compound causes its effects in the brain hasn’t been well understood. LSD is a member of a class of drugs called ergolines, which are used to treat many conditions, including migraine headaches and Parkinson’s disease. Understanding how the compound exerts its unique effects could provide insights to guide the development of future therapeutics.

LSD interacts with proteins on the surface of brain cells called serotonin receptors. Serotonin is a chemical messenger that helps brain cells communicate. LSD appears to act through a particular receptor called 5-HT2AR. To gain insights into LSD’s effects, a research team led by Dr. Bryan Roth at the University of North Carolina crystallized a related receptor, 5-HT2BR, attached to LSD. The scientists used x-ray crystallography to visualize the structure. Their study was supported by NIH’s National Institute of Mental Health (NIMH). Results were published on January 26, 2017, in Cell.

Serotonin receptors activate 2 major signaling pathways within cells: through G-proteins and through β-arrestins. The researchers found that LSD binds its receptor in a way that causes it to act mostly through the β-arrestin pathway instead of the G-protein pathway. Related ergoline compounds, the scientists found, differ in the way they structurally interact with the receptor. Further laboratory experiments and computer analyses revealed that these distinct but similar compounds can shape the structure of the receptor to trigger different effects.

The team also found that the serotonin receptor closes a “lid” over the LSD molecule, preventing it from quickly detaching. This likely explains the drug’s long-lasting effects. A mutant form of the receptor with a weaker lid had reduced β-arrestin pathway activity, while leaving G-protein pathway activity unaffected.

“This study sheds light on the mechanism of psychoactive drug action, including how certain drugs activate one signaling pathway inside cells while avoiding another,” explains Dr. Laurie Nadler, chief of NIMH’s Neuropharmacology Program. “Taken together with other recent studies of drug-receptor complexes, this work provides proof-of-concept for the design of drugs with desired signaling properties and fewer undesired side-effects.”

Roth and other colleagues recently showed the potential of such structure-based design. Based on similar discoveries about an opioid receptor, they created a molecule that effectively alleviates pain in mice, but with fewer side effects than morphine.


What cannabis actually does to your brain

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World’s Oldest Pot Stash Offered an Afterlife High

When archeologists opened the tomb of a Gushi shaman in northwest China, they found his stash. The…

Scientists have known for a while that the active ingredient in cannabis was a chemical called delta-9-tetrahydrocannabinol, or THC for short. Ingesting or smoking THC has a wide range of effects, from the psychoactive "getting high" to the physiological relief of pain and swelling. It also acts as both a stimulant and depressant. How could one substance do all that?

Meet the cannabinoid receptor

In the 1980s and 90s, researchers identified cannabinoid receptors, long, ropy proteins that weave themselves into the surfaces of our cells and process THC. They also process other chemicals, many of them naturally occurring in our bodies. Once weɽ discovered these receptors, we knew exactly where THC was being processed in our bodies and brains, as well as what physical systems it was affecting. Scattered throughout the body, cannabinoid receptors come in two varieties, called CB1 and CB2 - most of your CB1 receptors are in your brain, and are responsible for that "high" feeling when you smoke pot. CB2 receptors, often associated with the immune system, are found all over the body. THC interacts with both, which is why the drug gives you the giggles and also (when interacting with the immune system) reduces swelling and pain.

Cannabinoid receptors evolved in sea squirts about 500 million years ago humans and many other creatures inherited ours from a distant ancestor we share with these simple sea creatures. THC binds to receptors in animals as well as humans, with similar effects.

Tasty, tasty, tasty

Cannabis notoriously makes people hungry - even cancer patients who had lost all desire to eat. One study showed that cancer patients who thought food smelled and tasted awful suddenly regained an ability to appreciate food odors after ingesting a THC compound. There are CB1 receptors in your hypothalamus, a part of your brain known to regulate appetite, and your body's own cannabinoids usually send the "I'm hungry" message to them. But when you ingest THC, you artificially boost the amount of cannabinoids sending that message to your hypothalamus, which is why you get the munchies.

Understanding this process has actually led to a new body of research into safe diet drugs that would block those cannabinoid receptors . That way, your hypothalamus wouldn't receive signals from your body telling it to eat, and would reduce hunger cravings in dieters.

What you're forgetting

What's happening in your brain when smoking pot makes you forget what you're saying in the middle of saying it? According to the book Marijuana and Medicine (National Academies Press) :

One of the primary effects of marijuana in humans is disruption of short-term memory. That is consistent with the abundance of CB1 receptors in the hippocampus, the brain region most closely associated with memory. The effects of THC resemble a temporary hippocampal lesion.

That's right - smoking a joint creates the effect of temporary brain damage.

What happens is that THC shuts down a lot of the normal neuroprocessing that goes on in your hippocampus, slowing down the memory process. So memories while stoned are often jumpy, as if parts are missing. That's because parts literally are missing: Basically you are saving a lot less information to your memory. It's not that you've quickly forgotten what's happened. You never remembered it at all.

A bit of the old timey wimey

Cannabis also distorts your sense of time. THC affects your brain's dopamine system, creating a stimulant effect. People who are stoned often report feeling excited, anxious, or energetic as a result. Like other stimulants, this affects people's sense of time. Things seem to pass quickly because the brain's clock is sped up. At the same time, as we discussed earlier (if you can remember), the drug slows down your ability to remember things. That's because it interferes with the brain's acetylcholine system, which is part of what helps you store those memories in your hippocampus. You can see that system's pathway through the brain in red in the illustration at left.

In an article io9 published last year about the neuroscience of time, we noted :

How do you really know what time it is?

Why can't you tell when an hour has passed without looking at a watch? Why are you able to do…

The interesting thing about smoking pot is that marijuana is one of those rare drugs that seems to interact with both the dopamine and the acetylcholine system, speeding up the former and slowing down the latter. That's why when you get stoned, your heart races but your memory sucks.

It's almost as if time is speeding up and slowing down at the same time.

Addiction and medicine

Some experts call cannabis a public health menace that's addictive and destroys lives by robbing people of ambition. Other experts call it a cure for everything from insomnia to glaucoma, and advocate its use as a medicine. The former want it to be illegal the latter want it prescribed by doctors. Still other groups think it should be treated like other intoxicants such as alcohol and coffee - bad if you become dependent on it, but useful and just plain fun in other situations.

What's the truth? Scientists have proven that cannabis does have medical usefulness, and the more we learn the more intriguing these discoveries become. Since the early 1980s, medical researchers have published about how cannabis relieves pressure in the eye , thus easing the symptoms of glaucoma, a disease that causes blindness. THC is also "neuroprotective," meaning in essence that it prevents brain damage. Some studies have suggested that cannabis could mitigate the effects of Alzheimer's for this reason.

At the same time, we know that THC interferes with memory, and it's still uncertain what kinds of long-term effects the drug could have on memory functioning. No one has been able to prove definitively that it does or does not erode memory strength over time. Obviously, smoking it could cause lung damage. And, like the legal intoxicant alcohol, cannabis can become addictive.

Should cannabis be illegal, while alcohol flows? Unfortunately that's not the kind of question that science can answer. Let's leave the moral questions to courts, policymakers and shamans. I'll be off to the side, smoking a joint, thinking about my acetylcholine system and the many uses of the hippocampus.


Marijuana May Help Protect, Heal The Brain

Michael Harper for redOrbit.com — Your Universe Online
A new study from Tel Aviv University has found that THC, the psychoactive component in marijuana, can protect the brain from cognitive damage, especially following injury. Medical marijuana has been found to be beneficial in treating pain, insomnia and lack of appetite, but this study has found that THC also helps the brain protect itself before and after an injury.
Professor Yosef Sarne at Tel Aviv University’s Adelson Center for the Biology of Addictive Diseases at the Sackler Faculty of Medicine discovered this as he was performing experiments to discover the biological makeup of marijuana and tested his hypothesis on lab mice. His results are published in the journals Behavioural Brain Research and Experimental Brain Research.
According to Professor Sarne, only a very small dose of THC is needed to protect the brain from long term cognitive damage brought on by injury, seizures, or even damage from toxic drugs. Without this barrier of protection, brains are susceptible to cognitive defects and neurological damage.
This isn´t the first time THC has been found to protect brain cells. Previous research observed that, when administered 30 minutes before or after a brain injury, the psychoactive chemical could create a protective effect on the brain´s cells. Professor Sarne´s research, however found that the same benefits could be achieved if small doses of THC can be administered up to seven days before an injury or three days after. Only a small amount of THC is needed, which is about 1,000 to 10,000 times smaller than the amount found in a joint.
The basis of this discovery lies in cell signaling. The research team discovered that when administered, THC signals the cells to begin growing and even prevents cell death. To test their theory, Professor Sarne and team injected lab mice with very low doses of THC both before and after subjecting them to brain trauma. One group of mice was used as a control and was subjected to the trauma without any THC.
Three to seven weeks later, the researchers ran tests on the mice as they looked for signs of brain damage. Those mice that received a low dose of THC performed much better in these tests than the control group of mice that received no treatment. What´s more, the THC group of mice also had more neuroprotective chemicals in their system brought on by their treatment than the control group.
This treatment almost acts as an immunization to brain damage, although the drug has been found to cause minute brain damage. In small doses, THC conditions the brain to prepare for injury and build up its resistance. When used in the long term, this treatment could continue to protect the brain from any cognitive damage.
While it may sound difficult to predict when a person might experience brain trauma, Professor Sarne says there are several practical ways in which this treatment could be used to protect the brain. For instance, Sarne discovered this treatment protects the brain from injuries that occur due to lack of oxygen.
The machines used during open-heart surgery carry the risk of interrupting the supply of blood and oxygen to the brain. According to Professor Sarne, THC could be administered before this invasive surgery as a preventative measure. It´s long-term effects could also make it useful for those who have encountered a head injury in sports or vehicle accidents, and it´s low dosage is safe for people at high risk for heart attacks or even epileptics.

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