Heavy marijuana use may cause poor memory and abnormal brain structure, Study says


Teenagers who smoked marijuana daily for three years performed poorly on memory tasks and showed abnormal changes in brain structure, according to a Northwestern Medicine study.

Researchers in Chicago observed the brains of teenagers who were heavy users of marijuana. In those individuals, memory-related structures in the brain appeared to shrink and collapse inward, possibly indicating a decrease in neurons.

These abnormalities were recorded two years after the teens stopped using marijuana, possibly indicating long-term effects, and look similar to schizophrenia-related brain abnormalities.


For some reason, Canadians always seems to get their medical and scientific news several years ahead of us: :hmmm:

It was similar with the story of pharmaceutical waste being found in drinking water.

CBC Science Documentary: The Downside of High (originally broadcast during the 2009-2010 season of ‘The Nature of Things’ CBC TV Science program):


For more information:


(Unfortunately, you can only watch the program on the player if you are in Canada):


Here’s to YOUR Health.



What was the question again?


Title of thread should be “Heavy marijuana use may cause poor memory and abnormal brain structure in teens, Study says.”


Teenagers brains are less developed than an adult, they are still growing.




Well, I definitely do not find this to be surprising. Marijuana is a drug after all and drug usage can have severe affects on people.

That said, I currently support the legalization of marijuana solely for medical purposes at this time. Am I going against Church teaching by being for medical marijuana? If so then I am definitely going to abandon my support of the legalization of medical marijuana.


I’ve seen marijuana wreck many a teen’s life by sapping their ambition. School becomes a joke to them, and they end up dropping out. In their minds, why strive for success in schoolwork or sports when all it takes to feel good is some marijuana. The drug causes mental deception, and we all know who the father of lies is.


I completely agree that recreational usage of marijuana is wrong. I also completely agree that it can wreck teen’s lives. But is there really anything wrong with a cancer patient, for example, using medical marijuana to help severe symptoms that other medications either don’t manage or don’t manage well enough?


I always knew that it didn’t make people smarter. :shrug:


Yep. And heavy use of alcohol can cause liver damage. And overheating can cause diabetes. And driving fast can cause wrecks. And on and on.


Have you seen documentaries or chat shows that feature adults who take marijuana? When they take marijuana, don’t they often appear cognitively impaired? Do you think adults are as astute and alert when they’ve taken marijuana that they were before they took it?

The following article goes through the various chemicals in cannabis, and it seems that various chemicals in cannabis have an affect on brain chemistry



More bad moral decisions are made due to marijuana use than good ones.


I first smoked marijuana when I was 12. :blush: At 13, I was smoking it daily, and did so heavily until I was in my early 20’s, at which time I gave it up completely. I’m now 36.

…yes, it’s true I don’t have the greatest memory in the world, but I do think I’m pretty good at understanding complex concepts. As for my memory - it’s typically things I ‘did’ that are hard to remember, like what did I do last Monday… I have no clue… What was that guys name again…? It’s like that.

But I’m an expert speller. I can pass tests exceptionally well… I have a lot of love to give… :o

I do often wonder sometimes if I would have been a better person without having gone the route that I did though. :shrug: I dunno, probably so.


I never had much ambition when I was in high school and I didn’t smoke it though I think video games were my drug of choice back then and my form of escapism! I didn’t drop out of school though but my point is, this kid might have lacked ambition regardless of the cannabis. Just something to think about.


I see many people are confusing this study, it doesn’t demonstrate a definitive link. Remember correlation does not necessarily mean causation, the results therefore are ‘inconclusive’ and I see many people in this thread ignoring medical research to suit their own bias’.

In a fully grown adult the use of marijuana has been demonstrated to be less harmful then caffeine and substantially less harmful than alcohol. Impairment of memory has been demonstrated in a full grown adult to be only the case whilst the main active chemicals are still in the body at an active dose (which can be for a long time in heavy users) even if their normal function is not impaired. This however does not carry over to when the substance is at an inactive level in the system.

Also: a study was recently released from Belgium that demonstrated that the causal link between schizophrenia and marijuana use was tenuous at best. It had only been found due to the researchers begging the question (assuming the premise) and doing poor research that reeked of intellectual dishonesty and academic malpractice.

closed #17

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