March 13, 2006

Marijuana's impact on the Brain

While not specifically tied to the issue of schizophrenia - more scientific research has just come out demonstrating negative effects of marijuana use on the brain. And - less you think we have some bias against cannabis / marijuana - we were actually pretty ambivalent about it until all the research starting coming out on the negative effects on people's brain. This is relevant to people who have schizophrenia and continue to use marijuana - because it makes recovery even more difficult which is particularly important given that schizophrenia already negatively impacts cognitive abilities in many people.

The New Scientist (in the UK) states:

"Long-term users of marijuana gradually become worse at learning and remembering things, a new study suggests.

“It definitely fogs your brain,” says Lambros Messinis, who led the study at the University Hospital of Patras in Greece.

Messinis and colleagues tested the mental abilities of 20 long-term users who had taken marijuana heavily – smoking at least four joints a week – for an average of 15 years. Their brains were rustier than those of 20 short-term users – who had averaged seven years of use – and 24 controls who had used the drug sporadically or not at all....

“Long-term users found it very difficult to learn through new information given verbally,” says Messinis. “It’s not to do with lack of attention but more the encoding process of memory.” Separate tests to probe attention span found that long-term users were able to pick up information immediately, without trouble."

Source: New Scientist: Marijuana Fogs the Brain

More information: Schizophrenia and Marijuana / Cannabis


Although I find no real issue with the findings of this report, the following line is a bit obscure "...smoking at least four joints a week – for an average of 15 years. Their brains were RUSTIER than those of 20 short-term users..." I thought RUSTIER was an odd word to use in a scientific report, what the hell does RUSTIER mean in context of the findings? Metal rusts... not brains.

Posted by: mister at March 13, 2006 06:08 PM

Hi Mister - actually the magazine that we sourced this article from (the New Scientist) is a science magazine for the general public - thus the term "rusty" - which in layman's terms, tends to mean something that doesn't work as well as something else (ie. something that isn't rusty).

Posted by: szadmin at March 13, 2006 11:47 PM

I found the articele a bit nonscientific. It did not explain how the test were done and what the actual results were.
Maybe Marihuana smoking changes your perception while you are under it`s influence and a short while after it as it still remains in the body for a long time, but to believe that it totally damages your brain is hard.
Marihuana had been used for all sorts of remedies against all kinds of illnesses and it ts still used today. In any good book on herbs you will find that it is a powerful herb, not to mention it`s economical use, which is extraordinary for just one so simple plant.
The link to schizophrenia and other mental illnesses is to be dicussted. I have schizophrenia and I smoked marihuana long before I got it but I quit smoking it long before I got it too. One could say that that caused the illness. It is said that one percent of the general population has the illness but from the sixties on the use of cannabis as a drug has risen, so should the cases of mental illnesses but they did not.
I do not have hard time reading and remembering beacuse i use to smoke marihuana, but because of the illness and the drugs perhaps.

Thank you,


Posted by: Luka at March 15, 2006 09:07 AM

Hi, I don't see why anyone should have a problem believing what these research findings are saying. One piece of research has recently come out (possibly originating from the UK) indicating that it has effects on the neurological development of some part of the brain in adolescents who smoke it regularly over a period of years. Of course the adult brain is somewhat less malleable, but by necessity the parts which deal with memory have to remain plastic so that new memories can be encoded. I believe one of marijuana's actions is to reduce the normal inhibition of "long-term potentiation" - that is the mechanism by which connections between neurons that regularly stimulate one another are increased. Because your brain is firing in an altered state while this inhibition is taking place, this may lead eventually to significant, hard to reverse changes in structure of parts of the brain.

Posted by: Tris at August 29, 2006 04:53 PM

The problem is with the SMOKING, not the actual plant. Carbon Monoxide poisoning affects people in the way that it is often said that Cannabis affects people. Take the smoking away and instead vapourise and see the difference.

Posted by: Jean at September 25, 2007 12:51 PM

when will you people realize that marijauna is harmless? where are the #s showing deaths caused by canabis? oh wait, THERE AREN'T ANY! please focus on the quickly growing crack and cocaine problem not to mention the legal drugs that kill millions: tobacco and alcohol. why are people steadily focusing on something that is not harming anyone? besides, it is always a cognitive choice to use. so if you're having trouble learning hmmmmm maybe don't get high while you're studying!? no? yeah c'mon people use your brain. i know many students at my school alone who use marijuana and do better than those who've never used it! so maybe it's just because they don't get high while in school and studying. too much of anything is bad this is true however, one time use of crack can change your life forever. one time use of marijuana may cause extreme appetite o0o0o watch out! don't want that to happen. please lets focus on things that make a difference in the # of deaths in our country not the # of people who can retain the most information. what's more important to you?

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