How Cannabis Affects Our Cognition and Psychology

Summary: Researchers investigate how cannabis can influence a number of cognitive and psychological processes.

Source: The Conversation

Cannabis has been used by humans for thousands of years and is one of the most popular drugs today. With effects such as feelings of joy and relaxation, it is also legal to prescribe or take in several countries.

But how does using the drug affect the mind? In three recent studies, published in The Journal of PsychopharmacologyNeuropsychopharmacology, and the International Journal of Neuropsychopharmacology, we show that it can influence a number of cognitive and psychological processes.

The United Nations Office on Drugs and Crime reported that, in 2018, approximately 192 million people worldwide aged between 15 and 64 used cannabis recreationally. Young adults are particularly keen, with 35% of people between the ages of 18 and 25 using it, while only 10% of people over the age of 26 do.

This indicates that the main users are adolescents and young adults, whose brains are still in development. They may therefore be particularly vulnerable to the effects of cannabis use on the brain in the longer term.

Tetrahydrocannabinol (THC) is the main psychoactive compound in cannabis. It acts on the brain’s “endocannabinoid system”, which are receptors which respond to the chemical components of cannabis. The cannabis receptors are densely populated in prefrontal and limbic areas in the brain, which are involved in reward and motivation. They regulate signalling of the brain chemicals dopamine, gamma-aminobutyric acid (GABA) and glutamate.

We know that dopamine is involved in motivation, reward and learning. GABA and glutamate play a part in cognitive processes, including learning and memory.

Cognitive effects

Cannabis use can affect cognition, especially in those with cannabis-use disorder. This is characterised by the persistent desire to use the drug and disruption to daily activities, such as work or education. It has been estimated that approximately 10% of cannabis users meet the diagnostic criteria for this disorder.

In our research, we tested the cognition of 39 people with the disorder (asked to be clean on the day of testing), and compared it with that of 20 people who never or rarely used cannabis.

We showed that participants with the condition had significantly worse performance on memory tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) compared to the controls, who had either never or very rarely used cannabis. It also negatively affected their “executive functions”, which are mental processes including flexible thinking.

This effect seemed to be linked to the age at which people started taking the drug – the younger they were, the more impaired their executive functioning was.

Cognitive impairments have been noted in mild cannabis users as well. Such users tend to make riskier decisions than others and have more problems with planning.

Although most studies have been conducted in males, there has been evidence of sex differences in the effects of cannabis use on cognition. We showed that, while male cannabis users had poorer memory for visually recognising things, female users had more problems with attention and executive functions.

These sex effects persisted when controlling for age; IQ; alcohol and nicotine use; mood and anxiety symptoms; emotional stability; and impulsive behaviour.

Reward, motivation and mental health

Cannabis use can also affect how we feel – thereby further influencing our thinking. For example, some previous research has suggested that reward and motivation – along with the brain circuits involved in these processes – can be disrupted when we use cannabis. This may affect our performance at school or work as it can make us feel less motivated to work hard, and less rewarded when we do well.

In our recent study, we used a brain imaging task, in which participants were placed in a scanner and viewed orange or blue squares. The orange squares would lead to a monetary reward, after a delay, if the participant made a response. This set up helped us investigate how the brain responds to rewards.

We focused particularly on the ventral striatum, which is a key region in the brain’s reward system. We found that the effects on the reward system in the brain were subtle, with no direct effects of cannabis in the ventral striatum.

However, the participants in our study were moderate cannabis users. The effects may be more pronounced in cannabis users with more severe and chronic use, as seen in cannabis use disorder.

There is also evidence that cannabis can lead to mental health problems. We have shown that it is related to higher “anhedonia” – an inability to feel pleasure – in adolescents. Interestingly, this effect was particularly pronounced during the COVID-19 pandemic lockdowns.

Cannabis use during adolescence has also been reported as a risk factor for developing psychotic experiences as well as schizophrenia.

One study showed that cannabis use moderately increases the risk of psychotic symptoms in young people, but that it has a much stronger effect in those with a predisposition for psychosis (scoring highly on a symptom checklist of paranoid ideas and psychoticism).

This shows a drawing of a woman with cannabis leaves in her hair
Tetrahydrocannabinol (THC) is the main psychoactive compound in cannabis. Image is in the public domain

Assessing 2,437 adolescents and young adults (14-24 years), the authors reported a six percentage points increased risk – from 15% to 21% – of psychotic symptoms in cannabis users without a predisposition for psychosis. But there was a 26-point increase in risk – from 25% to 51% – of psychotic symptoms in cannabis users with a predisposition for psychosis.

We don’t really know why cannabis is linked to psychotic episodes, but hypotheses suggests dopamine and glutamate may be important in the neurobiology of these conditions.

Another study of 780 teenagers suggested that the association between cannabis use and psychotic experiences was also linked to a brain region called the “uncus”. This lies within the parahippocampus (involved in memory) and olfactory bulb (involved in processing smells), and has a large amount of cannabinoid receptors. It has also previously been associated with schizophrenia and psychotic experiences.

Cognitive and psychological effects of cannabis use are ultimately likely to depend to some extent on dosage (frequency, duration and strength), sex, genetic vulnerabilities and age of onset. But we need to determine whether these effects are temporary or permanent. One article summarising many studies has suggested that with mild cannabis use, the effects may weaken after periods of abstinence.

But even if that’s the case, it is clearly worth considering the effects that prolonged cannabis use can have on our minds – particularly for young people whose brains are still developing.


Barbara Jacquelyn Sahakian receives funding from the Leverhulme Trust and the Lundbeck Foundation. Her research work is conducted within the NIHR Cambridge Biomedical Research Centre (BRC) Mental Health and Neurodegeneration Themes and the NIHR MedTech and in vitro diagnostic Co-operative (MIC). She consults for Cambridge Cognition.

Christelle Langley is funded by the Leverhulme Trust.

Martine Skumlien receives funding from the Aker Foundation.

Tianye Jia receives funding from the National Natural Science Foundation of China.

About this cognition, psychology and cannabis research news

Authors: Barbara Jacquelyn Sahakian, Christelle Langley, Martine Skumlien, and Tianye Jia
Source: The Conversation
Contact: Barbara Jacquelyn Sahakian, Christelle Langley, Martine Skumlien, and Tianye Jia – The Conversation
Image: The image is in the public domain

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  1. I do not believe this. I am 60 and a very detailed orientated successful business woman who was raised in the 70s. Thank God recreational use has come to us 40 years later. No cognitive problems or psychological. Your study is not correct. Talk to all the 60 year old users then we will talk!

  2. 10% not half bad. I would still like to see the statistics though and I’m sure you couldn’t get a proper number of individuals to come up with a proper percentage. That 10% only falls under the number of people y’all were able to study which I’m sure is less than 1% at best of the population. With that being said those numbers don’t really mean anything in the grand scheme of things. And if this “drug” but really a plant taps into our natural state of being then it’s obviously something that’s a part of us. Let’s talk about alcohol a bit more than cannibus because that is a real epidemic in this world

  3. Has your research looked into other abnormalities like skin diseases or infections, allergies on longtime usuage. What about children of parents that are users

  4. Iam 63 years old, I have all of the above mentioned side-effects and I am in agreement with your study, very informative and the facts are the facts my using it since 1976 and still use it but had slow down because I was affected by all your findings. I had cancer and used the codes in combat my cancer and use to from higher thc presentage to help me sleep and maintain my weight. I also use phytocanabadois from the hemp plants with 0 thc from verdant oasis. Thank you for your studies and I have been slowing my use because of the mentioned side-effects

    1. This article is complete bullshit and the author should be ashamed of themselves for peddling such propaganda, the proof that it helps with such an array of problems caused not just by life, but pharmaceutical effects on the brain/body, is overwhelming, myself included, my work productivity, overall happiness, and quality of life have only improved, which is also aware to those around me, shame on you false peddlers of lies.

  5. Did they do these types of extensive studies for alcohol? It’s literally a poison to our bodies but yeah whatever. The big violent elephant in the room agrees that we should demonize cannabis even more, bc it’s not a poison.

    1. I want to start off by saying I think alcohol is WAY worse than weed will ever be. But, with that being said, I also think we need to take a step back and ease into legalizing weed. I’d also like to point out that, although not near as bad as alcohol, weed is very much toxic for your body… Depending on consumption of course, which leads to some being worse than others. Inhaling any smoke or vapor from weed is introducing toxins to your body. Edibles are relatively safe in my opinion, but can easily be abused and lead to unsafe amounts of THC in your body. All in all they need to legalize simply because of the amount of money it would generate for our states and country. Sure it has dangers, but not a single one more deadly than alcohol. Age restrictions of 18+, 21+, or even 25+(brain fully developed in most) would be obvious

    2. Yeah,i love all the scare tactics used in this article,but if anyone does just simply research,the positive attributes of cannabis out-wiegh the negatives, specifically when it comes to pharmaceuticals,but i also thought like ADAM, why don’t they do the same research for alcohol?and then see the real reason why were all fukd up from the start…. accepting alcohol as our one true legal drug due to the fact that it’s shoved in our faces from the 1st memory,till our dying day

  6. Since only 10% of cannabis users meet this diagnostic criteria I feel confident in saying cannabis is still safer than anything Pfizer or Merck manufacture. Lastly stop referring to cannabis as a drug, it’s a plant. Fentanyl is a drug.

  7. Complete nonsense. I smoked for 20 years, during which I read non-stop, obtained a bachelor’s degree, and became one of the smartest people in the world. I suspect this “study” was funded by Anheuser Busch.

    1. You sound very egocentric. Bragging about one’s smartness is not attractive.

  8. Well I am 60 years old I been smoking sence I was 21,I don’t have to take pain pills any more. I don’t have any depressing, so y’all study with your so-called pharmaceutical companies are a bunch of fucking liar. you’re not making enough money off
    cannabis.Your trying to hurt everybody because of Your greed.!!

    1. Hey i in recovery 6 months after an stroke, cerebral aneurysm, intracranial hemorrhage and a damn eye stroke..ive been smoking since I was 16 to help me relax and help me to calm .then I broke my neck 2004 and have the white coat sydrome shit. Well the past 18 years im so grateful I was smokes the marijuana it has helped me with the high blood pressure I had and no doctor ever helped me . I was never tested for HBP. So 8 did do my study
      .waited on my Blood pressure pill from blood pressure was 156/90 I smoked and with on 10 minutes I took it again and went down to 126/76 So it has saved me …but if you have broken cervical issues you dangerously high for blood pressure..and get it checked or you will have stroke shit or heart shit

      1. Man, after reading your post my observation is that you are barely literate. It sounds like most of your medical and psychological problems are probably self induced. White coat syndrome is just another one of those crackpot diagnosis for the last several generations of people who can’t cope and need and excuse for their lack of maturity and abilities.

        1. so you’re saying Laura gave herself an intracranial hemorrhage, stroke, aneurysm and broken neck. talk about a “crackpot diagnosis”! and your diagnosis of her being unable to cope and having a lack of maturity and “abilities” is incredible! thank you doctor know it all.

    2. 100% agree. I started smoking 2 years ago and I am pharmaceutical free now. And feel better than I ever have and I lost 40 lbs. I don’t overeat because of depression anymore. I feel free and happy for the first time in my life…

    3. I find your publication very useful and informative. Thinking back to my youth I started using pot at 16 years and turned into heavy use it definitely negatively affect my cognitive ability and brought out psychotic symptoms and I didn’t have before use. I am completely clean and sober today and starting to get my life back. My Hope is that this helps adolescents that are tempted to experiment with cannabis when their brains are fragile. I find this information true. Respectfully David M.

    4. I believe this is 100%false information, it’s been proven to have with cancer, glaucoma, pain ,anxiety & more ,why wouldthere be Marijuana Dr. &regular Dr’s try to make people understand, that it’s helpful , &get off of opioid, unless this is from.the f.d.a. so more money can be spent on drugs,

  9. Im 58 year old female living in san diego for 45 years and I have been smoking marijuana for 40 years everyday and I havent noticed anything different to myself except im fatter thats because marijuana gives you the munchies so I snack more thats it nothing more theres no side affects to smoking marijuana im proof of that I dont smoke cigarettes and I havent been to the doctor’s in 28 years how bout that science brain doctors and collage kids enjoy your day cause im about to enjoy a bong hit myself

    1. Typical bs. Bet not a single 1 of you have ever even tried Marijuana!!! I truly doubt it! If any 1 of you have you’d know how much it makes a difference! I haven’t smoked pot for 20 years but I have always been very open minded with those who do + I am very happy with the decision to make it legal for ANY OF THE PEOPLE WHO USE IT!!! I’M QUITE SATISFIED WITH THE IDEA AND I THINK IT MIGHT be worth my time to get a prescription myself to control my migraine headaches which I had very rarely when I actually did use it!! Believe what you want but maybe you should research this more! Thanks for the bs!!!

  10. I use cannabis everyday and all this is bullcrap ?I use/need it as medicine and I don’t get ANY negative effects of what was printed on this post or whatever it’s called ?

  11. 38 subjects to lead this story? That an exploratory study at best. 780 teenagers? Drawing any conclusions with these low number is not enough to draw any firm conclusions. At best, they are experimental forays to suggest the a need for more definitive, broad cohort, or longitudinal studies. What isn’t up are definitive conclusions.

  12. I’m 40 and have smoked regularly for 25 years. Never once have I had a psychotic episode and on the contrary pot is the one thing that has kept my bipolar mood swings in check. Not the countless pills that produced side effects of varying degrees. This is a horribly misinformed article and is one sided. Do better “scientists.” This isn’t 1940 quit with the Reefer Madness bullshit already.

  13. Well done is what I want to say, but I feel like there may be biased perspective on users,for instance nothing was said about the assessment of users while high and their performance under it’s influence, terming it a drug also feels heavy handed as most of the community prefer the term herbal supplement,as it’s use can vary wildly in form from raw smoking to cooked dishes and baked goods, which also vary the effects across a wide range. You wouldn’t study the effects of vitamin c without one group actively using it while the other used a placebo, I don’t understand how this counts as a true experiment and accurate data if the scientific method wasn’t followed fully, I could run this experiment and get entirely different results mostly because those doing the study didn’t examine the culture in-depthly enough. – regards DailyToker.

  14. I have smoke pot for along time. Still do I”m 67 now. Have been doing so since I was 15. I worked all my life without problems.35 years in a/c heat dealing with people I had no problems.

  15. Please. Cannabis use, recreationally and responsibly, is harmless. Been that way since way before the word neuroscience was even invented. Outliers exist, but mainstream users are generally, fully functional. Your user cohort is inaccurate – stand outside any retail dispensary in WA state and watch the broad spectrum of humanity stroll in and out all day.

  16. You have found a correlation between cannabis use and specific executive dysfunction, but that is not causation.
    I have found in my work as counsellor that many undiagnosed people with ADHD often self-medicate with various drugs, including cannabis. The experiment group needs to be assessed for other factors that will impact executive functioning, otherwise your data isn’t significant in any way.

    1. Please cut down on the logic here its putting cracks the designed study above. But on the real if people are using this as medication (many many are) than it would be beneficial to see how they perform off AND ON the substance they use daily to really measure. Either that or have the sober group use cannabis the day of if skewing potentially useful data is the goal

    2. I felt very informed on the article you wrote on the effects of cannabis products on the brain and the mind. I was a casual user at some era of my young adolescent to adult life. I have truly been concerned with my cognitive functions also. I was drawn to marijuana because I thought it made me more creative and imaginative. I also thought it enhanced my sexual experiences which I didn’t see mention of in the article. But truth be told, I have found reasons to really believe that I was effected in my using days. I also used crack for a period of two episodes of my life. Factors such as these may put another twist on the studies performed. I have drank alcohol also. But I have been clean and sober for @12 years now. Still I can’t seem to think as clearly as others in my peer group. Your article shed some light on my dilemmas. For that I am grateful for you. I wish you continued success in your studies and endeavors. I’m Gary Bradger….

  17. Yet again a study on Cannabis that repeats previous finds and that is completely blind to other effects. Like creativity. Why people consume Cannabis, to think “out of the box”. The advantage of this is difficult to quantify, but to conclude only on negative effects of the substance as a general conclusion is just a conservative bias.

  18. You folks better start studying actual life long skateboarders who are still learning new tricks and smoke industrial amounts of weed. Seriously. For science sake, study this existence that is me and others like me

  19. Okay, who did the editing in this article. Would the sentence these sex effects beside the controlling for age yes s e x when it should have been s i x. I heard of some college students wanted to get medical marijuana cuz it helped them study and go longer yes there is good and bad with it. Although, if you guys keep on making this the first drug that a human being has text used abused. How many of you had alcohol, when you were children? Also the ones who wrote the anger thing on a cannabis, that’s funny, only I think it’s 5% of the ones that do smoke get violent. Yeah I do my reading,on I’m basically anything medical. thank you have a good day have a good night.

  20. This is a bunch of propaganda and has no real scientific value. As a chronic user that has mental health disorders I personally found that I can have a more normal life and less mental health episodes. But of course I didn’t start using until my late 20s.THC affects everyone differently just like medications for physical sicknesses. People who don’t have mental health disorders should not consume THC. That is fact.

  21. When I read symptoms of impaired executive function and memory, I can’t help but think of primary ADHD being a factor. Even more so, with the mention of addictive behaviors and reduced responses to stimuli. ADHD also tends to present with more inattentive symptoms in females, and impulsivity in males (which may, I’m unsure, correlate with memory impairment). The findings in the study all seem to reflect these known relationships between ADHD and its presenting behaviors/symptoms.

    With ADHD being one of the most under diagnosed learning disabilities (though arguably also considered by some, one of the most over-diagnosed), I wonder how the data and/or findings may change when subjects are adjusted for the incidence of ADHD—it’s possible a much greater portion of those with ADHD seek and abuse cannabis. To avoid the possibility of ADHD secondary *to* early cannabis use, it can be determined whether such subjects showed signs of ADHD earlier in life prior to cannabis use.

  22. I started smoking in my mid twenties. When I was younger I noted, in response to the negative side effects mentioned in your article, some memory challenges. However, my ACE scores and my ongoing trauma, poverty,lack of family and Christian love support attributed to this more so or in addition. As I got older, I smoked less, as I matured. In addition, I’ve always been an overachiever so weed motivated me. I had better weight training workouts. (I did those workout at 5am when the gym was quiet so I could keep my mind focused on my lifting of free weights and on proper breathing. I think this study has a lot of cracks and needs reevaluating. I agree with early weed smoking hindering the mind. Especially if one has never been motivated to begin with or who never desired to perservere. Nature or lack of can cause one such as me to escape the traps of my past generations which included sexual trauma at very early ages and ongoing up until my adult years. Of course, I have more insights on myself more now. Overall, I like weed on occasions to calm my mind and to increase my creativity. I’m “labeled schzoidphrenic” but Idont really hear voices but receive messages. Talk to Dr. Eleanor Longdon, a lead researcher. She helped saved me from the bonds of society’s impression of mental “capabilities” I’m more telekinetic than twisted or crazy. I’m not crazy. I’m very smart. . God Bless

  23. There is a difference in THC and CBD, I see it all the time, CBD can be good when helping health problems because it isn’t psychoactive, users cannot get a high, therefore it is okay even if in the cannabis family, however cannabis with THC is what we are really discussing, because it may damage the brain of users, whereas CBD can only help fight health issues, including cancers without getting high, so why is it necessary to praise CBD? Users know they want to get high and THC fulfills that desire.

  24. It is apparent that cannabis is destroying young smokers brains with psychotic experiences, possible chronic paranoid schizophrenia in the future. Perhaps there should be a black label warning that states long-term use of cannabis smoking can cause brain damage that may or may not be permanent. If that is truly the case then where are the studies and trials to create a cure, or reduce the addiction to cannabis?

    Not much at all in the works to withdraw the cannabis disorder addiction.
    I believe that all that people who profit from the sale of cannabis should be required to pay a small % of profit to a fund to develop a cure to fight addiction and find a cure for schizophrenia.

  25. Reefer madness was written a long time ago. Is this the 21st century version?

  26. The world cannot listen to this type of bias when so many use the substance for its benefits.
    Next time include positives, it makes this website looks decades out of date as there is a plethora of research very readily available from much better credited sources.

    1. THC is for getting high, CBD which your referring to is great, helps many health issues, but no one is asking that CBD be stop. THC just causes cannabis disorder due to long term issue, psychotic experiences and possibly schizophrenia, so there is a difference.

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