"Heavy Marijuana use shrinks brain parts"

[Nickatina]

They were not significant. There were too many variables to call this study conclusive.

Why weren't these volumes compared to an average across a larger sample size instead of directly to the non-smokers in the study? They could have measured the size of their eyes and it would show a proportional difference. What if the non-cannabis smokers had larger brains overall and in effect larger volumes of the hippocampus and amygdala? There was nothing done to account for this possible variable. They could have compared the volume of what they measured to the volume of the brain overall, instead of directly to the non-users.

They never told us what a joint constitutes in size, if the users were high during the tests or not, and they are relying on information given by the users themselves, saying that they smoke 5 or more joints a day and never used other drugs.

The mean age was lower in the non-smokers, could that effect the sizes?

There are far too many variables to draw any type of scientific conclusion.

 

[Ernestrome]

They were not significant. There were too many variables to call this study conclusive.

Why weren't these volumes compared to an average across a larger sample size instead of directly to the non-smokers in the study? They could have measured the size of their eyes and it would show a proportional difference. What if the non-cannabis smokers had larger brains overall and in effect larger volumes of the hippocampus and amygdala? There was nothing done to account for this possible variable. They could have compared the volume of what they measured to the volume of the brain overall, instead of directly to the non-users.

They never told us what a joint constitutes in size, if the users were high during the tests or not, and they are relying on information given by the users themselves, saying that they smoke 5 or more joints a day and never used other drugs.

The mean age was lower in the non-smokers, could that effect the sizes?

There are far too many variables to draw any type of scientific conclusion.

Results: Cannabis users had bilaterally reduced hippocampal and amygdala volumes (P = .001), with a relatively (and significantly [P = .02]) greater magnitude of reduction in the former (12.0% vs 7.1% ). Left hemisphere hippocampal volume was inversely associated with cumulative exposure to cannabis during the previous 10 years (P = .01 ) and subthreshold positive psychotic symptoms (P < .001). Positive symptom scores were also associated with cumulative exposure to cannabis (P = .048 ). Although cannabis users performed significantly worse than controls on verbal learning (P < .001), this did not correlate with regional brain volumes in either group.

They were significant. I'm assuming you actually understand what statistical significance is, would you like a wikipedia link for your edumacation?

 

[Nickatina]

Edit: No ad-homs, please. -phrozen

I am saying the results were not significant in the sense that it means nothing conclusive. The statistics were skewed, any significant differences don't mean shit because the study don't mean shit. I see you did not try to rebuke any of the points I brought up, just the reference to insignificance in which you twisted the meaning of my words. Bravo.

 

[PriestTheyCalledHim]

Define "heavy" use.

 

[MyDoorsAreOpen]

Nickitania, you need to cool it.

If we're going to pick apart this study, let's attack the details of the study itself, not other people's opinions on it.

 

[Ernestrome]

Define "heavy" use.

Multiple joints a day for years?

 

[Ernestrome]

They were not significant. There were too many variables to call this study conclusive.

Why weren't these volumes compared to an average across a larger sample size instead of directly to the non-smokers in the study? They could have measured the size of their eyes and it would show a proportional difference. What if the non-cannabis smokers had larger brains overall and in effect larger volumes of the hippocampus and amygdala? There was nothing done to account for this possible variable. They could have compared the volume of what they measured to the volume of the brain overall, instead of directly to the non-users.

What if, what schmif. Maybe they did have larger brains, maybe...

They never told us what a joint constitutes in size, if the users were high during the tests or not, and they are relying on information given by the users themselves, saying that they smoke 5 or more joints a day and never used other drugs.

I wager most people don't know how much they put in each joint. It's a very imperfect measure, but it's probably the best you can do when you're trying to assess use dating back over many years.
Measuring blood and urine levels would've been a useful check.

The mean age was lower in the non-smokers, could that effect the sizes?

Yes, i believe it could.

There are far too many variables to draw any type of scientific conclusion.

There are problems with the study, but this doesn't mean you bin it.

 

[jesse_wg]

I believe insignifigant results such as these should not be published anywhere. they should just be used as an outline to start more in-depth studies. once they test further then those results should be published. stating that this test is what led them to go more in depth looking at the amygdyla and hippocampus

To say that these results such as these should not be published anywhere means to rule out any further research which is building on this. If results are not published from studies that may have some methodogical issues that need tweaking (which studies don't?) then how is anybody to know what exactly needs changing.

Although there are definitely some problems with this research, what you also need to understand is that perfect research only occurs in a perfect world. To get participants in a longitudinal study which assess neurological deficits is very difficult - especially if they're smoking weed!!! To get a decent sample size in this kind of research also requires a large degree of funding. Unfortunately research like this gets minimal funding...

So yes, there are a number of issues with the study. However, just as in ecstasy research - which I'm involved in - taken together with a range of other studies employing different methods, there is fairly convincing evidence that cannabis causes neurodegeneration. If you want more proof speak to anyone that smokes it on a regular basis and I'm fairly certain I know what their response will be.

 

[swilow]

there is fairly convincing evidence that cannabis causes neurodegeneration

Hmm, theres also evidence suggesting that THC can help neuro-regeneration, especially in instances like Alzheimers (yeah, in mice but hooray!). I've been smoking pot for the last 12 years, I'm 26, and certainly don't feel brain damaged.

 

[jesse_wg]

Sorry, I was probably exaggerating a little when I said speak to 'anyone', but certainly I know a lot of people (including myself) that feel as though weed has contributed to memory impairment (which would link to possible neurodegeneration).

I also wasn't denying that there are studies showing the contrary. But from my limited research of cannabis use, it appears as though the majority of research points to it generally being neurodegenerative, or certainly causing cognitive impairment.

But hey, I'm open to any and all research that shows the contrary. Indeed there is some research that shows cannabis might be neuroprotective against the possible serotonergic neurotoxicity from MDMA use. What I was trying to get at was that although the quoted research had flaws, some people were saying it shouldn't be reported, and I think that is absurb.

 

[Dxmmonster]

15 people?? seriosuly?

 

[swilow]

Sorry, I was probably exaggerating a little when I said speak to 'anyone', but certainly I know a lot of people (including myself) that feel as though weed has contributed to memory impairment (which would link to possible neurodegeneration).

I also wasn't denying that there are studies showing the contrary. But from my limited research of cannabis use, it appears as though the majority of research points to it generally being neurodegenerative, or certainly causing cognitive impairment.

Hehe, I wish I could disagree but I can't. My memory is poor-to-average according to Miss Swilow (quick consultation ), though whether thats from pot or benzodiazepines, I know not. Perhaps pot smokers tend to disregard things that simply aren't important? :D It would be interesting to know what specifically in terms of short term memory is impaired. For example, I remember facts easily, which helps when studying; however, stuff like keys, phones, books etc. tend to get waylaid constantly. I guess they are different 'types' of memories....

I tend to think that, as THC is so lipid soluble, that for moderate-to-heavy smokers (weekly-to-daily) the drug is never fully excreted. Its obvious that whilst being stoned, one's short term memory is fucked; theres good reason to think that, whilst subjective effects appear nil, THC is still active in parts of the brain. From my experience, if I stop smoking heavily for a few weeks, I begin remembering things a lot better. I would think that actually being affected by cannabis certainly causes some neural 'problems', but once the drug is pretty much eliminated from the body, these go. I haven't seen enough evidence to show that this is a long-term degeneration as such.

BTW, I'm Aussie too, from Melbourne I saw your study post in DS, was kinda interested...?

Peace

 

[jesse_wg]

Hehe, I wish I could disagree but I can't. My memory is poor-to-average according to Miss Swilow (quick consultation ), though whether thats from pot or benzodiazepines, I know not. Perhaps pot smokers tend to disregard things that simply aren't important? :D It would be interesting to know what specifically in terms of short term memory is impaired. For example, I remember facts easily, which helps when studying; however, stuff like keys, phones, books etc. tend to get waylaid constantly. I guess they are different 'types' of memories....

Interesting you say that because there are actually different types of memory, and different structures in the brain are involved in these areas. The hippocampus has been implicated in the laying down of new memories (such as remembering where you put your keys), whereas it's generally believed that once memories have been consolidated they are 'stored' in areas of the cerebral cortex. This could explain your ability to recall facts easily but problems with remembering where your keys and phone are!

In terms of other drugs thats a huge problem in drug research (especially in my research on ecstasy use), although it is much easier to find cannabis only users. It doesn't sound like that controlled for that in this study further weakening it...

Ohh and cool that you're in melb! Glad you saw my study! It's quite interesting to be doing, if you'd like to participate drop me an email or message. It only takes about 20 mins, and once I'm finished (end of Oct) I can give you the results too.

And for all you people bagging out this thread's study for low sample size, I'm expecting to have over 1200 participants!

 

[swilow]

This could explain your ability to recall facts easily but problems with remembering where your keys and phone are!

But its new facts as such....For example, I now know ridiculously stupid things about the Bronte` family if your interested, but to get in my car would take about ten minutes of rather crap searching before Miss Swilow rescues me again. :D

 

[Enlitx]

Ya, I don't know if you guys have taken a stats class, but p-tests measure significance much better than your assumptions. Like I stated at the very beginning of this posts, be ready for all the posts denying the credibility, pot smokers wouldn't want to admit their drug of choice might actually have some downsides! Like I stated, seperate studies have determined that THC reduces the activity of the hippocampus, so why is it hard to understand that over time your brain would reduce the size of this structure?

 

[Care]

Ya, I don't know if you guys have taken a stats class, but p-tests measure significance much better than your assumptions. Like I stated at the very beginning of this posts, be ready for all the posts denying the credibility, pot smokers wouldn't want to admit their drug of choice might actually have some downsides!

I actually have taken a stats class (hated it, but passed it anyways) and one of the most important factors in inferential statistics is SAMPLE SIZE.

Say what you want about funding causing a lack of test subjects, but there is a direct correlation between the margin of error and a small sample size.

Especially in studies that can be interpreted as politically motivated like this one you have to be very picky about the details. It is very likely that the 15 people chosen were not even close to an accurate representation of the general pot smoking population. The 15 people could have been specificly chosen as geneticly likely to have smaller brain sizes than the control group, and we would never know. Its much much harder to pull this off when you have say....500 subjects.

Studies like this is EXACTLY how misinformation gets spread. They cut corners and rig the information to say what they want it to say.

 

[Nickatina]

What if, what schmif. Maybe they did have larger brains, maybe...

For someone who is arguing the scientific fact in a study, it seems "what if, what schmif" doesn't cut it.

There are problems with the study, but this doesn't mean you bin it.

See I never said we shouldn't draw a possibility out of the study. All I am saying is that there is not enough evidence to even base a media article out of it. It didn't prove ANYTHING, period. I am not one to argue for a drug just because it is a drug ... in fact I have already stated my resentment towards weed because I do believe it just holds people down. But if we are going to make a statement saying it, in effect, causes brain damage, then we better make damn sure that it does. And this study does nothing to solidify that.

 

[swilow]

Ya, I don't know if you guys have taken a stats class, but p-tests measure significance much better than your assumptions. Like I stated at the very beginning of this posts, be ready for all the posts denying the credibility, pot smokers wouldn't want to admit their drug of choice might actually have some downsides! Like I stated, seperate studies have determined that THC reduces the activity of the hippocampus, so why is it hard to understand that over time your brain would reduce the size of this structure?

Just compensate by doing crosswords, brain puzzles, sudoku etc...

 

[Enlitx]

Just compensate by doing crosswords, brain puzzles, sudoku etc...

Heh, thats what I tell my fiancee to do so she won't develop dementia later on .

 

[Ernestrome]

For someone who is arguing the scientific fact in a study, it seems "what if, what schmif" doesn't cut it.



See I never said we shouldn't draw a possibility out of the study. All I am saying is that there is not enough evidence to even base a media article out of it. It didn't prove ANYTHING, period. I am not one to argue for a drug just because it is a drug ... in fact I have already stated my resentment towards weed because I do believe it just holds people down. But if we are going to make a statement saying it, in effect, causes brain damage, then we better make damn sure that it does. And this study does nothing to solidify that.

You're arguing hypotheticals, what's scientific about that?