Marijuana and the Teenage Brain

| Modified on Jun 01, 2021
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Most people have heard that hemp and marijuana are the same. After all, people have been using hemp for at least 2,500 years to make rope, shoes, clothes and even paper. It is still being cultivated, primarily in China, and they export hemp to the U.S. and other countries. It is undeniably a very useful plant. 1

Marijuana, Hemp and Potency

However, saying that hemp and marijuana are the same is like saying that a housecat is the same as a tiger. Hemp and marijuana are different varieties of Cannabis sativa.2 Modern marijuana is not even the same as the marijuana grown in the past. Today's marijuana is up to ten times more potent than the joints they passed around at Woodstock. Some users in the Netherlands smoke a variety that is THIRTY-THREE times more potent. 3 That ain't your grandpa's weed. As is true of other illegal drugs, users can never be sure exactly what they are buying on the street when they buy marijuana. The NIH reports that the long-term consequences of smoking more potent marijuana are unknown. 4

How Does Marijuana Make People Feel 'High'?

THC (Delta-9-tetrahydrocannabinol) is the primary active ingredient, the reason people smoke pot. Marijuana's effect on the brain is felt very rapidly and lasts up to three hours. If marijuana is consumed in food or a beverage, the effects are not felt for up to an hour but remain for up to four hours. THC attaches itself to cannabinoid receptors (CBRs); these are receptors in the brain linked to pleasure and tactile sensations, memory, and concentration, coordination, and time perception. In other words, the overstimulation causes users to feel 'high'.

What is Marijuana's Effect on the Brain?

The CBRs are located on neurons in the brain which is an extensive communication network. The neurons 'talk' to each other, like radio transmitters; the CBRs function like fine-tuning knobs. If the neurons and CBRs are not communicating properly, memory, decision-making, and other normal brain activities are disrupted. The 'high' feeling is produced because THC displaced normal brain communication, acting somewhat like static on a radio.

Endocannabinoids are chemicals similar to cannabis that the body produces to carry messages throughout the body. Specialized proteins (enzymes) create and destroy endocannabinoids as needed. The endocannabinoid system refers to the messengers (endocannabinoids), receptors (CBRs), and enzymes. Marijuana interferes with this system, one of the backbones of brain function.

What is the Effect of Marijuana on Teenager's Brains?

When children become adolescents, their brains do not produce as many CBRs as when they were younger, but their brains produce more of the enzymes that create the messengers (endocannabinoids). This implies that brains need messengers to assist in communication within the brain. The teenage brain is in a transition stage between childhood and adulthood. The endocannabinoid system is working during the teen years to help shape the communication networks that will become the adult brain. The teen brain is a 'work in progress, not the completed masterpiece.

This is why it is believed that marijuana use during the teens can have more significant and long-lasting effects on young brains than marijuana has on adult brains. The THC in marijuana attaches to parts of the brain that are developing and growing, changing the communication network within the brain.

Is There a Link Between Marijuana and Mental Illness?

Ongoing studies of the brains of schizophrenic people have found changes in the endocannabinoid system. This may be why people who have used marijuana, especially when they were teens, are more likely to develop mental illnesses such as schizophrenia; they also develop these illnesses earlier than they develop within the general population.

To grossly oversimplify, the implication that can be drawn is that an external influence (marijuana) influencing and changing normal brain development is not a good thing. Marijuana use among students in grades 8-12 was once again trending up as of 2011. Almost one-third of high school seniors had used marijuana within the past year, and there's a reasonable likelihood that the marijuana was fairly potent. 5


TV and movies have popularized the image of a 'pothead' as someone slow-thinking, forgetful, not ambitious and 'mellow'. While this is often an exaggerated caricature, marijuana does interfere with quick-thinking and how well a person forms new memories, thus negatively affecting learning. Coordination and reaction time are affected, making driving and complicated tasks more difficult. 4 The pleasure gained from smoking marijuana is temporary, but marijuana's effect on the brain appears to be permanent.


1. Hemp History. "The History of Hemp."
2. The Cap Times. "What's the difference between hemp and marijuana?" 3/17/2010.
3. Cecil Adams. "Is marijuana stronger than it used to be?" The Straight Dope. 4/20/2012.
4. National Institute on Drug Abuse. "How does marijuana use affect your brain and body?"
5. Dr. Leonora Long. "Cannabis and the endocannabinoid system: an interview with Dr. Leonora Long." 10/15/2012

About The Author

Mary Post has been researching and writing on health, financial and technical subjects for over thirty years. Health problems suffered by family and friends led to extensive research on health issues, hunting for better answers to their problems. Mary lives near Tampa, Florida.

Marijuana and Mental Health Issues

Posted by Elaine (Va) on 11/26/2013

I, too, have family members who felt 'it's only pot' and now have mental health issues. From the pot? I don't know, but the fact is that they have an illness now that non-pot smoking members of a very large family do not have. There may be a genetic component, as this is a large family with many double first cousins (sibling marry siblings, then their children marry, etc). Recipe for genetic upset, I know. As for the pot, I think it wise to not take it at least until the body is fully mature--why risk damage to a developing body with a non-essential item? I'm okay with my elderly mother using it for glaucoma or pain relief; she no longer drives and if it makes her life easier I say okay. That leaves the young-adult to retirement age group. I am not okay with getting wasted, and any impairment at all is not okay to be out driving, etc. The impaired individual rarely thinks he is impaired, and there's no test. Also, younger people help themselves to their parents tobacco and alcohol, so you can't control it in the home. This is a problem. Bottom line, we should take good care of ourselves and this means probably no mind-altering substances.

Replied by Timh
(Ky, Usa)
2073 posts

To not distinguish chronic or excessive Pot use in youth from occasional or moderate is an error of thinking. Bad premise and procedure always end w/ bad conclusions and results.

Marijuana and Schizophrenia

Posted by Karen (Santa Barbara, California) on 11/26/2013

I was very glad to receive your latest article on marijuana and the brain. I have a story to share with you. I had a brilliant friend who started with pot in the 1960s. Like many others during that time, he also dropped acid. As he aged, he became extremely delusional and thought various groups were after him. I believe now he had undiagnosed and untreated schizophrenia. He self medicated with marijuana because it was the only thing that made him feel better. However, as one of his closest friends who saw him frequently, I saw that the marijuana made his delusions much worse. The more delusional he became, the more pot he smoked. It was a vicious cycle. He was so miserable. No one in his family or circle of friends could get him the help he needed although we tried and tried. One day he took his own life to end his misery. It was very sad.

One day, a year or two before his death, I tried a small amount of his "medication", pot he said was from Thailand, only the 2nd time in my life to do so. It made me so extremely paranoid for the few hours it was in my system, I almost went to the ER. It makes me shudder to think how many teenagers are smoking it daily thinking it's harmless. Until you've watched a loved one falling apart before your very eyes, you don't really know.

Marijuana and Schizophrenia
Posted by Candance (Nebraska) on 11/25/2013

Interesting article, I enjoyed reading it as I have heard many times that the use of cannabis could have an effect on the brain with teenagers but never had anyone explained in detail how it could effect the brain.

My son was diagnosed with Schizoeffective when he was 20 years old. The illness runs in the family as his father had it also. We have learned to control it via a combination of diet, supplements, meds AND cannabis.

Without all three he quickly goes downhill. It has taken us 10 years to get to where we are now. I don't know about the teenage use and the connection with the illness I just know it runs in the family. But I do know without it now he has issues. We have had him tested several times for temporal lobe epilepsy as it can have the same symptoms as schizophrenia and it has been proven cannabis use can help improve it but so far they have not been able to find any signs of it with my son.

Whether it was genetics or cannabis use that caused this illness for my son I don't know but I do know now without it his brain does not function normally.

I would strongly suggest that if anyone has a teenager and if there is any history of mental illness in your family, share this information with your teenager. Mental illness is very devastating and robs you of your future.

Marijuana and the Teenage Brain

Posted by Kevin (Victoria, Australia) on 11/27/2013

WOW, you guys just brought in a whole lot of controversy as always. It doesn't appear that this is going to change for obvious controlling governmental reasons. For the main part, marijuana, pot whatever you want to call it, is not a drug. 10-33 times stronger, not likely or one would find themselves overdosing quite easily and feel very uncomfortable.

As far as teens smoking it and having the growth of their minds altered, well that is an ongoing study. Some people I have witnessed benefit from smoking weed, some get slower and lethargic and lazy. It all depends on the individual, however, like most nonsensical scientific diatribe, we all seem to get lumped into the ONE category.

People are all different in the way the makeup of their bodies respond to marijuana. I, personally, do not like the initial feeling of getting high, but I feel great shortly afterwards. Some people never know when to stop or moderate with marijuana use, thus abusing something that could be of benefit to them.

Once again, I feel this article has been manipulated by the big pharmaceutical industries and besides why are the pharma companies trying to create a synthetic form of marijuana and market it. Is it because there are more benefits to the use of MJ than not? If they can market a patent on this plant then I guess there are billions of dollars to be had now isn't there.

All this rhetoric about motor skills being slowed down and so forth. I have witnessed people becoming heightened in their awareness, so once again the individual has been wrongly categorized by pseudo science. It all depends on the dose, besides shouldn't we be concerned of the millions of people driving in their vehicles everyday that have just taken their pharma medications and are completely impaired at the wheel of their 4000lb vehicle??!!! Yes, really now, wake up. More people are impaired by prescription drugs than alcohol and marijuana combined. But I guess most people would not comprehend this primarily because most people live in a comatose-brainwashed state of mind since the introduction of chemtrail pollutants and microwave radiation and whatever else the controlling forces of this messed up planet would throw at us.

Also, when you grow marijuana under synthetic light and unnatural soil and with chemical bug sprays, it is not the natural plant anymore and yes, you may call it a drug since the original intent of the plant has been altered. So who is to blame for this then? The ones who want to control MJ!! If it was a free plant, and notice I did not say LEGALIZED!! , all would be well on this planet. Man has not learned to leave things alone, especially the creators laws. Until then, my name is Kevin.

Replied by Gavin
(Northland, New Zealand)

The main thing to remember is that the young brain has enough troubles programing itself during the post puberty period. Mary Jane and any other psychotropic stuff, legal and illegal should be avoided until maturity. Unfortunately the young brain only gets one chance at this, common sense suggests that it's best to stay clear. If taken as an adult the mature human brain has set itself a fall back position. So occasional use doesn't seem to be a problem. Same goes with alcohol.

Replied by Timh
(Ky, Usa)
2073 posts

Back in the day when being "high" in the wrong place at the wrong time needed some assistance. I would pop a daily vitamin, w/ a cup of Java, fallowed by 500mg vit-c and sober up enough to get thru it. Also, as an aid to brain health during any kind of stress ---Lecithin. There are several manufacturers marketing "triple strength lecithin" which would certainly provide all day support and more. The Choline in lecithin is both a fat burner and a detoxifyer; so the choline would certainly be indicated for the lipid cannabinoids. Along w/ other nutrients like the daily multivitamin, will support a cleaner "high" by reducing the side affects like paranoia and oversensitivity.


Posted by Susan (Los Angeles, Ca) on 02/21/2014

On the subject of Marajuana and the Brain, Dr. Daniel Amen's team put out an interview on the subject:

and SPECT scan images of drugs like marijuana on the brain:

Slowed Brain Function

Posted by Gina (Texas) on 11/25/2013

hmmm. my two cents: in my 40 years of marijuana experience I know personally only two people whose marijuana use slowed their brain function when they weren't using. both are male, both started smoking shortly after they reached puberty. one was in the 70s, so he wasn't smoking strong weed. the other has been since 2000, so he was. the first guy wasn't that bright to begin with, the second was. he is still smarter than the average bear, but not near as quick as before. I have heard from other people of men who've been affected that way, but never heard of it happening to a woman.

Replied by Jutza98
(Fort Collins, Co)

Nice article!! I am sick and tired of people defending how a person is affected by pot. The idea that pot is harmless is just wrong, it is not harmless, it is a mind altering drug, plain and simple!!!

People who smoke pot and drive are no different than those who drink and drive, or take prescription medication and drive - all have impaired thinking and "slowed brain functioning"!!

Anyone who believes the fantasy that pot is harmless is living in their own fantasy world.

Perhaps people need to work as a death investigator and see what the "harmless" pot does to people. Driving while only smoking pot has killed the driver as well as those innocent other people either in the same vehicle as the "slowed brain functioning" pot smoker, or an innocent sober driver in another vehicle. Pot is a depressant and I cannot count the number of suicides that have occurred with the only thing in the person's system was THC!!!

I don't care what another person does to their own minds and bodies, however, let's quit the pretending that pot is harmless and cures so many ailments. If they want to promote it as a medicine, then regulate it as such.

I personally have seen way too many people affected by pot. Just as some people are more hyper on alcohol, so are some people on pot. Another lie is that all people who ingest pot are mellow. That is as wrong as saying all people who drink are hyper and crazy.

It always amazes me how people also claim that pot is not addicting. I want to know why then do they spend so much time getting their next fix of pot? If they spent as much time trying to get a job as they do to score some weed they might just lead a happier life and not be so depressed!!

I also personally know several individuals who smoked/ingested pot for many years only to be later diagnosed with BiPolar Disorders. Again, like the issues explained in this article continual use of marijuana might just get the user a serious mental disorder by altering their brain functions with what they think is "harmless"!!

Replied by Prioris

The number one problem with drugs is making them illegal. This allows the state to artificially manufacture crime and help build up the police state out of thin air. Many people will rail against drugs while turning a blind eye to state involvement on all levels.

Too much water can be damaging to ones health. What the study neglects to do is determine how much is too much. There is risk in almost everything. As far as marijuana use, we're talking about a broad spectrum of use by people.

When we're talking about addiction, different substances have different addiction profiles. Someone can be addicted to heroin or smoke cigarettes but still lead a normal life.

btw I don't use marijuana.