[QUOTE=Dj Yoshi]There's no conclusive evidence that it causes brain damage. And if you know what a cannabinoid receptor is and if it gets damaged in the process of smoking marijuana, please, enlighten me instead of pseudo-scientific babble that is just mainly name-dropping of some pieces of the body. It's like saying "Oh yeah? Drinking coke doesn't cause heart attacks? So do you know what a heart is?"
Give me more info, and not pages of info. Tell me, because I don't need to be poring through health manuals meant for people much more educated in the field than I am trying to make sense of it.[/QUOTE]
#1
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16148447&query_hl=4&itool=pubmed_docsum
#2
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16527424&query_hl=2&itool=pubmed_docsum
The cannabinoid receptor CB1 is located in various areas in the brain. One of these areas, the hippocampus, is the "center for learning and memory". Basically, it is involved in consolidation of memory, spacial location, ect.
#1: A cannabinoid agonist (such as THC) has been shown to basically suppress neural function in this region, by inhibiting excitatory neurotransmitter release (there are inhibitory NT's as well; this works on excitatory). This has been shown with THC.
#2: This one shows developmental concerns. THC injected perinataly causes deficiencies involving cogntive imparement.
Now, you can very easily say "prenatal and short time use, yeah, but who says that there are lasting effects brought on by chronic use of deh chronic?" That's a good question. Use of SUPER agonists to the CB1 receptor (over 100x more powerful than THC) can cause permanent LTD (long term depression, bad thing) in portions of the limbic system (of the brain, which includes the hippocampus). But that's not THC, which is found in MJ. You can't really truly compare the two; it shows a possibility, but THC is much weaker. Keep in mind this is done on rats who have a short lifespan. You can't study a rat on 10 years of THC use, they'd be dead by 3 years. The studies just show possibilities, but I could not say THC does it, at all even.
One point is that short term malfunctions are shown, and usually the way the brain or any system works is that if you give chronic doses of an agonist, it messes with the current internal system. There are endocannabinoids (reefer to Sci Am's article), and possibly the chronic use of THC makes the body dependent on it, and it downregulates the endogenous source. It just takes lots of time, which is why rat studies use the super agonist.
Also, it's higher mental function, which is difficult to assess small changes in. Forgetting a little bit more or not being at your "peak" isn't something one can quantify. If can be a very small change; damage was done, but you just wouldn't notice because the brain has enough resilience to cover it up a bit.
In the end, I don't know, and can't say for certainty that THC causes brain damage. It may. It's likely to me based on other systems, but that's a "gut feeling". But nothing using THC has shown that it does, mainly because of a time frame issue, and the fact it's higher mental function. However, you on the other hand cannot say with certainty that it
doesn't cause damage.
I mean, there are studies (
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11233294&query_hl=7&itool=pubmed_DocSum) That say that yes, indeed, chronic THC causes problems, but there are ones that counter them. Sadly, it's a politically charged area, so I'm going to stick with my "it's likely it does, but not for 100%" stance.
Also, there are possible positive benefits, such as possible inhibition of neural degeneration in MS, and of course antidepressant effects. There are also other weird occurances, like neurogenesis WITHOUT differentiation. New cells, but how they get used... who knows? Just thought I'd add that.
Oh yeah, the super agonist is:
http://en.wikipedia.org/wiki/HU-210
Also, I forgot to mention tolerance buildup, which also effects use of endocannabinoids. Anyway, I could add to this for days, but it's long already.
Basic point: THC short term causes short term mental dysfunction. Long term has not been shown with THC but with other agonists. THC can "fool" with internal biology of endocannabinoids. No study has conclusively shown brain damage with THC, and studies regarding benefits are not conclusive either (except the antidepressive part). It's good to play it safe and not use it, because there are no real appreciable benefits to the common person, and there are potential risks.
On a tangent, chronic MJ is relatively minor compared to chronic Alcohol and Tabbaco, and hell, even unhealty food. I'd be happy if the only unhealthy sin people took part in was MJ.