While it’s getting legalized in more and more parts of the world…
Sometimes outrageous claims, are being made both by proponents and opponents of the use of this controversial plant.
Proponents of the Herb of Herbs are pointing out countless positive effects of this medicinally active plant…
Opponents of legalizing marijuana are pointing out a myriad of dangerous effects supposedly related to using this plant…
In this current chaotic atmosphere where anyone can spread anything they want about the use of marijuana…without backing it up with any form of science…
What can you believe…?
And how can you decide whether marijuana is for you or not?
Thus the critical question remains:
What are the current FACTS on the effects of marijuana…on the brain?
Why the brain?
Because the brain is the control chamber of the human mechanism…and every effect except the physical effects of marijuana (in other parts than the brain) are based on the chemical changes…
…that happen in the brain.
But in order to really understand the effects of marijuana on the brain, first we have to understand HOW marijuana affects your brain…
How Does Marijuana Affect Your Brain?
This complex medicine plant contains over 500 of known compounds…and probably over 1000 unknown compounds.
What really sets marijuana apart from the other plants in the vegetable kingdom, is a specific type of compound only found in the marijuana plant:
Cannabinoids are the compounds mainly responsible for ALL the effects of marijuana…whether it’s on the brain or body.
So What’s the Deal with These Cannabinoids?
This is a very complex process but here’s a simplified version:
By acting on these receptors, these cannabinoids change your brain chemistry temporarily…especially in particular parts of the brain where the amount of these cannabinoid receptors is larger than in other parts.
And these chemical changes in your brain result in:
- (Neuro)protective effects;
- Changes in your psychomotor abilities;
- Changes in your cognitive processes;
- Changes in your perception, mood and consciousness (psychoactive);
- Potential changes in your mental health in the long-term, and;
- Potential physical changes in your brain in the long-term.
And then there’s the distinction that has to be made, between acute (short-term) and long-term effects…
I don’t know about you…but if something is going to have a negative impact on my control chamber (my brain) in the long-term…
…I will probably avoid it, unless the benefits outweigh the risks.
The negative short-term effects on the other hand, I will be more lenient with.
Let me explain:
If my memory takes a hit for a single day after using some marijuana…but it helped me relax and blow off some much needed steam for that day…it’s fine with me. If it would lead to memory decline in the long-term, I would definitely avoid it though.
ALRIGHT MAN…CAN WE JUST GO TO THE FACTS NOW?
Acute Effects of Marijuana on the Brain
The acute effects are the effects that are IMMEDIATELY noticeable…
Especially the acute psychoactive effects, are more subjective and individual than the long-term effects on the brain.
Why does this matter?
Although we’re talking about facts here, your personal experience under the influence of marijuana actually IS a FACT to you…even when science doesn’t back it up.
Let’s say your concentration usually is better under the influence of marijuana…if one study finds that the concentration of people under the influence of marijuana, generally speaking is much worse than sober people…
The FACT for you is that YOUR concentration is better.
The acute effects of marijuana are extremely personal and in the end, you will have to experiment for yourself and find your:
- desired mode of use: smoking, vaping (recommended!) or eating;
- your desired type of strain and;
- your desired type of setting.
Tip: the most convenient and healthy way to use marijuana is to vape it with a marijuana vaporizer.
All these variables will have a HUGE influence on especially the acute psychoactive effects of marijuana on your brain.
It gets better:
There are definitely certain acute effects on the brain which get reported the most by studies and users under the influence of marijuana.
Brain damage after strokes and trauma
So go ahead and take 1 puff of your vaporizer (yes…vaping is better than smoking, trust me) before your next headbutt battle.
Neurogenesis is the process by which new neurons are generated in the brain…and it seems at least some compounds in marijuana have the potential to help this process.
In a study done in 2013, Brazilian researchers found that the cannabinoid CBD increased neurogenesis, specifically in the hippocampus…in mice. So no it’s not directly translatable to humans. Plus you have to realize most marijuana strains currently on the market are very low on CBD. So you’ll have to look for high CBD strains to get this specific benefit.
CBC is another cannabinoid which seems to help neurogenesis. A study done in 2013 found that CBC has a positive effect on the viability of ‘adult neural stem progenitor cells’…again in mice. So again this study is not directly translatable to humans, but it definitely is giving hope.
It’s no coincidence that the use of marijuana has an immediate effect on your on your…wait for it…psychomotor skills.
So what does science say?
Chances are high your psychomotor skills will be impaired after you’ve used some marijuana. With the general rules that:
- The more THC is in your system, the worse the impairment, and;
- The less frequent you use marijuana, the worse the impairment (essentially the lower your tolerance, the worse the impairment).
In a meta-analysis of 150 experimental studies which looked at the effects of marijuana on physical activity, researchers found that smoking marijuana acutely impaired (to different extents) the following physical performance areas:
- Psychomotor skills;
- Divided attention;
- Visual functions;
- En- / Decoding
- Reaction time.
How can you actually use this information?
Please just don’t go driving while under the influence of marijuana…especially the first few hours after smoking / vaping it your psychomotor skills, attention and reaction time CAN be severely impaired ( I also speak from experience).
Is this always the case? And is it possible that you have no issues driving while under the influence of marijuana?
Yes…ultimately it’s your own decision. But really, why take the risk?
Besides driving…just try to avoid any type of physical activity in which it’s possible to hurt yourself or others AND which needs a high level of attention, reaction time and / or high degree of psychomotor skills.
These are very essential skills for even basic survival…so it’s no coincidence that a lot of research on the effects of marijuana on the brain is looking at the effects on specific cognitive skills (also this is somewhat objectively testable compared to subjective psychoactive effects).
So what is the current state of affairs with regards to acute effects of marijuana on cognitive skills?
With regards to effects of marijuana on cognitive processes, all ‘facts’ in this article are based on the 2 largest systematic review studies which analyzed over 50+ studies which looked into this topic (both acute and long-term effects):
- A 2003 study (Non-acute (residual) neurocognitive effects of cannabis use: A meta-analytic study), and;
- A more recent 2011 study (An Evidence-Based Review of Acute and Long-Term Effects of Cannabis Use on Executive Cognitive Functions).
Attention / concentration
In an analysis of 5+ experimental studies which focused on the acute effects of marijuana on attention / concentration researchers from the 2011 study found mixed results:
- Infrequent users of marijuana can experience some impairment in their attention and concentration skills, however…
- Heavy chronic users actually got better at attentional processing when they were under the influence of marijuana.
A possible explanation the researchers give is that chronic use of marijuana may result in your brain adapting to the marijuana exposure in such a way, that your brain actually normalizes…while under the influence of marijuana.
What does this mean for you?
If you’re a recreational user, just be careful of partaking in activities which require a high level of attention in which you may hurt yourself or others (i.e. don’t go operate the air traffic control tower under the influence of marijuana…if you happen to work there).
Decision-making and risk taking
Here the current state of affairs is again mixed…
With regards to risk taking, there are studies which do find acute intoxication with marijuana can lead to increased risk taking. However there are also studies which don’t find such a correlation (all of these studies can be found in the 2 systematic review studies).
With regards to decision-making it seems there are as many studies which find no impairment on the ability to make the right decision, as studies which do find such an impairment. One thing most studies do find though is that the process of making a decision does slow down significantly.
In other words:
Other than the fact your decision-making process will slow down…no real facts here.
This is one topic where almost all studies and researchers are on the same page:
- Marijuana use does immediately significantly impair working memory.
So just be sure to write a note with where you put your keys BEFORE you decide to fly off to a different dimension, the next time you decide to vape it up.
Verbal fluency is the ability to generate words in a set amount of time. And according to the 2011 systematic review study, the acute effects of marijuana on the brain do not seem to influence your ability to speak fluently.
However according to the 2003 systematic review study, marijuana use does seem to have a small impact on your verbal / language skills.
In other words:
The results are again mixed…and no real facts can be given here.
All I would say is don’t go smoking a big fat blunt before you have an important appointment or presentation.
Psychoactive (the high)
This feeling that we call the ‘high’ is obviously subjective…but when a lot of people report the same types of feelings during a high, it gets pretty damn close to fact.
So take the acute psychoactive effects at heart, but with a grain of salt!
Also realize that the psychoactive effects of marijuana are highly dependent on set and setting.
What do I mean by this?
If you’re already feeling down and you decide to smoke/vape some extremely high THC strain, in a chaotic environment like a crazy ass techno party…chances are the psychoactive effects of marijuana won’t be very pleasant! (or they might be…as said this is very personal and subjective)
With that being said…in the largest study which looked into the psychoactive effects of marijuana, the most common feelings which are being reported by users are the following:
- Sensory alteration;
- Changes in appetite;
- Changes in perception of time;
- Clearer thinking;
- Exaggeration of mood.
There are also some common negative feelings being reported:
How do you avoid these negative feelings?
As said before…
Ultimately, you’re going to have to experimenting with the following variables:
- Your mode of use (I prefer vaping);
- Your marijuana strain (I prefer Indica strains);
- Your set and setting (I only vape marijuana when I’m already in a good mood, and in a calm environment)…
…and find your own sweet spot.
Long-Term Effects of Marijuana on the Brain
‘Long-term’ is one of those terms that can basically mean anything…
Is it 1 week…is it 1 year?
Since we’re scrutinizing the results of scientific studies…
I’m kind of bound to use the same definition as most of these studies use, so long-term means:
- 21+ days since last using marijuana.
Important to mention is that in most studies where any long-term effects were found, users had the following characteristics:
- They started at an early age (before 17), and/or;
- Used marijuana heavily (daily and a large amount of marijuana).
This is all makes very much sense…when you look at the fact that the human brain is still developing heavily in many areas during adolescence (currently it is even thought the human brain is not fully developed until the mid-twenties).
Plus it’s only logical that heavy and daily use of any psychoactive substance over a longer period of time, which temporarily alters your brain chemistry …has the potential to alter your brain (chemistry) in the long-term.
And since this alteration of brain chemistry is actually a physical process…
We start with the current facts on whether marijuana use leads to any physical changes in the brain.
Heavy and chronic use of any psychoactive substance has the potential to change your brain volume and brain chemistry in a significant way.
But is there any evidence for marijuana?
Currently the only brain part of which can be said it’s possible a significant reduction in volume (in the form of grey matter) can occur, with HEAVY and FREQUENT marijuana use…is:
- the hippocampus.
The hippocampus is mainly associated with short-term memory, long-term memory and spatial navigation…
If this is the only brain part where significant physical changes have been found to occur in the long-term…
Are the long-term (neuro)protective, cognitive and mental effects also closely related to functions associated with the hippocampus?
Let’s find out.
Science has actually shown that certain compounds in marijuana have strong (neuro)protective effects on the brain. And according to some studies marijuana definitely has the potential to be used as a treatment for various diseases that have their origins in the brain.
In a study done in 2008, researchers found that the most well known compound in marijuana: THC, is a considerably superior inhibitor of Aβ aggregation than currently approved drugs prescribed for the treatment of Alzheimer’s disease. Aβ aggregation is the key process which leads to loss of neurons in Alzheimer’s disease.
A more recent study in 2014, also confirmed that THC is effective at lowering Aβ aggregation at extremely low concentrations in a dose-dependent manner.
This means marijuana use over a longer period of time could stop Alzheimer’s disease in its tracks.
The 2 most well known cannabinoids in marijuana:
- THC, and;
…have been shown to stop the growth of one of the most aggressive cancers in adult humans: glioma (a specific type of brain cancer). Especially combined with traditional radiotherapy, THC and CBD have been shown to be absolutely detrimental to glioma.
The current state of affairs with regards to the long-term effects of marijuana on cognitive skills are anything but clear and conclusive (like many, many things in science).
According to the 2011 systematic review stud that looked into the effects of marijuana on cognitive skills, there seems to be no effect on basic attentional and working memory abilities…
But there seems to be an impairing effect on decision-making, concept formation and planning…that is with users who either:
- Started early (before they were 17),and /or;
- Used marijuana heavily (daily and large quantities of marijuana).
Regarding the effects on any other cognitive skill…no ‘facts’ can really be given.
But is there any actual evidence of marijuana use leading to long-term mental imbalances?
First of all:
Any causal links between marijuana use and mental health issues have not been proved…yet. So in any study that finds a correlation between the use of marijuana and mental health issues, the question remains:
Is it really marijuana which is causing mental health problems or something else (i.e. lifestyle, diet, etc.)?
With this major caveat in mind…
There have been numerous studies and systematic review studies which have looked into this topic.
And the results are again…surprise, surprise: mixed.
We start with psychosis and mood disorders, because historically, marijuana use has been associated as a major cause of these mental diseases…
…but based on what exactly?
Let’s find out.
Psychosis and affective diseases (mood disorders)
…found that marijuana use can increase the risk of developing a psychotic illness and affective diseases later in life. According to the researchers the risk actually increases 1.4 times…
This is by no means a small amount if you ask me…
There are 3 factors which seem to highly contribute to such a risk:
- Existing susceptibility to psychotic illnesses;
- Onset of use in adolescence years (before 18), and;
- Heavy and frequent use of marijuana.
So take this 1.4 factor with a grain of salt…
BUT, be extremely careful with marijuana if you think you might be susceptible to any form of psychotic disorder.
General psychological issues
Besides looking specifically at psychosis and mood disorders, there have been many studies which looked at any association between marijuana use and general psychological health issues.
In the largest systematic review of at least 16 studies which looked at the relationship between marijuana use and general psychological health issues, researchers found very mixed results.
In the end they essentially concluded that there is no evidence of an association of marijuana use with psychological health issues…let alone marijuana use causing psychological health issues.
The researchers in the systematic review study ‘think’ no causal link between marijuana and psychological has ever been found, because no such link exists.
Conclusion and How Can (Should?) YOU Use All of This Information
So now that you’ve barreled through and have come to the end of this huge wall of extremely interesting, informative and useful text…
You’ve now got a clear idea what the current facts are regarding the effects of marijuana on the brain:
The acute effects are mostly personal and subjective, but marijuana does definitely have the potential to impair psychomotor and some cognitive skills. The psychoactive effects are extremely subjective but some positive effects which seem to be universal are relaxation, euphoria and sensory alteration.
But be careful…you might be sensitive to marijuana or used a little bit too much and these positive effects could turn into anxiety and paranoia.
The long-term effects of marijuana on the brain are far from conclusive…
Let’s first start by repeating one very important piece:
- You start using marijuana while young (below 18 years), and/or
- Use it heavily and frequently, and/or
- You have a susceptibility towards psychotic disorders…
…chances are, the effects of marijuana on your brain in the long-term might not be very pleasant:
- A few cognitive skills definitely seem to get impaired;
- Also your hippocampus could shrink in volume;
- And especially if you have any sort of susceptibility towards psychotic disorders, you could experience mental health issues at a later point in life.
What’s the bottom line?
Marijuana has MANY benefits all the way ranging from physical, mental and social…
But there’s no denying the fact that:
Like with every substance…use it too much and it can turn into poison.
What are the most important tips for responsible marijuana use based on the latest scientific research?
- Unless you have a medical condition and marijuana is your medicine…don’t be using marijuana daily and heavily (yes ‘heavily’ is subjective…but you get the gist);
- If you’re under 18 years old, wait it out or use marijuana very sparingly;
- If you think you might be susceptible to psychotic disorders, use marijuana extremely sparingly…or find strains which contain little THC and a lot of CBD;
- Since it’s determined that it’s THC which is responsible for the psychoactive effects of marijuana, marijuana growers have been modifying their plants in a way that the THC content of their plants basically sky-rocketed. If you ask me this is not natural, so I would advice to find strains which have a more balanced THC/CBD ratio and are grown in an organic way.