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Bullshit study. Sampling of 40 people means nothing. Also, it said that certain parts of brain changed in terms of shape and density but did not determine wheth

Bullshit study. Sampling of 40 people means nothing. Also, it said that certain parts of brain changed in terms of shape and density but did not determine whether this is a bad or good thing. In addition, I would like to know who funded the study.

diminoten 12y ago
It is not true that a low sample size means a high amount of variability. Depending on the people chosen, you can have a very low P value with as few as 26 or so participants. It should be more interesting to you how reactive you were to the headline of this submission, than to the results.
former_pothead 12y ago
It's not bullshit, below are similar studies: MARIJUANA USERS HAVE ABNORMAL BRAIN STRUCTURE AND POOR MEMORY - http://www.northwestern.edu/newscenter/stories/2013/12/marijuana-users-have-abnormal-brain-structure--poor-memory.html http://www.northwestern.edu/newscenter/stories/2013/12/marij... Persistent cannabis users show neuropsychological decline from childhood to midlife - http://www.pnas.org/content/early/2012/08/22/1206820109.abstract http://www.pnas.org/content/early/2012/08/22/1206820109.abst... From personal experience, I smoked recreationally from 18 to 24 and definitely felt serious, structural changes in my brain. I won't go into the details since it's anecdotal evidence, but if research like what I linked to and the OP was presented to me, I would have dropped it. People need to be aware there are consequences to your mental development if you smoke marijuana casually. Obviously the government has blown them way out of proportion, but the problems still exist.
- Im_Talking 12y ago
  The studies do not show causation, only correlation. And one of the studies was funded by the NIDA which will only fund studies which show harm. It is possible that the opposite is true: that people with a predisposition to mental illnesses use cannabis to self-medicate.
  - former_pothead 12y ago
    Even if that were true, it would mean the general population should be assured by a medical professional that they are not predisposed to mental illnesses before they use cannabis.
    - Im_Talking 12y ago
      You misunderstood me. I am saying that cannabis is not the culprit, in fact it helps. People use cannabis to self-medicate so use will be higher in people with mental illnesses. http://www.leafscience.com/2013/12/08/marijuana-cause-schizophrenia-harvard-study-finds/ http://www.leafscience.com/2013/12/08/marijuana-cause-schizo... http://www.leafscience.com/2014/03/25/marijuanas-effect-memory-overstated-study-finds/ http://www.leafscience.com/2014/03/25/marijuanas-effect-memo... http://www.leafscience.com/2014/03/20/5-ways-cannabis-help-fight-alzheimers/ http://www.leafscience.com/2014/03/20/5-ways-cannabis-help-f...
  - waps 12y ago
    This is not a valid point against medical studies, because medical studies never attempt to prove causation. They are merely showing that event A preceeds event B with correlation of 0.51 or so. The human body is so complex that controlling for every variable is simply not possible. It's not just funding either. To control for every variable you'd need more test subjects than there are humans alive. Furthermore all medical double-blind studies do indeed only show correlation (nearly always very low correlation, a successful drug will have correlation coefficients of maybe .53 If you find a drug for almost any disease that correlates with curing any disease of .7 or .8, you can start a pharma company and it'll be worth billions). Also while correlation does not imply causation, it does mean 1 of 3 things. Suppose A and B correlate. Let's take a flu medication and getting cured as an example. 1) A causes B (people who take the drug tend to get cured from the flue as a result) 2) B causes A (people who get sick, and heal by themselves tend to take the drug because they feel sick) 3) A and B are both caused by the same thing (can be many things, e.g. the medicine salesman has the flue) There have been attempts to mathematically define causation as correlation with a time offset (the one that preceeds is the cause, the one coming after is the result). This has had only limited success. That of course does not stop nearly every study outside of the pure sciences from taking such time-delayed-correlations as proof of causation. Are you really suggesting throwing out 99%+ of science over that ? ( and 4. you made a mistake and while it looks like correlation, it's not. E.g. longterm correlations in chaotic variables, like taking the .999999999999999999 correlation between mathematical descriptions of planetary orbits and concluding those planets are actually in those orbits until something large happens [1]. Yes it goes for earth too. The orbit of the earth could alter to throw the earth into the sun, or out of the solar system and there would be little or no warning. There is also no need for "large" events to cause this. Planets' movements do not follow the central limit theorem and therefore cannot be predicted with 100% certainty. The huge problem is of course, that in the real world nearly every problem exhibits chaos, for obvious reasons, not just the stock market) [1] http://en.wikipedia.org/wiki/Three-body_problem http://en.wikipedia.org/wiki/Three-body_problem
a_bonobo 12y ago
Paper: http://jn.sfn.org/press/April-16-2014-Issue/zns01614005529.pdf http://jn.sfn.org/press/April-16-2014-Issue/zns01614005529.p... The statistical treatment looks solid, good p-values and they even controlled for multiple testing with an adjusted p-value cut-off (alpha) of p < 0.0125 Funding is a bit biased: This work was supported by the National Institute on Drug Abuse (Grants 14118,026002,026104,and 027804 to H.C.B. and Grant 034093 to J.M.G.), the Office of National Drug Control Policy, Counterdrug Technology Assessment Center (Grants DABK39-03-0098 and DABK39-03-C-0098), and the National Institute of Neurological Disorders and Stroke, National Institutes of Health (Grant 052368 to A.J.B.). H.C.B. was also supported by the Warren Wright Adolescent Center at Northwestern Memorial Hospital and Northwestern University, Chicago.J.M.G. was supported by a Harvard Medical School Norman E. Zinberg Fellowship in Addiction Psychiatry Research Figure 1 has the gist, interestingly, gray matter density slightly increased with Marijuana usage. The changes weren't that extreme for the most part, but statistically significant. The L accumbens has the largest F (Table 2), indicating a larger difference in gray matter density, the other areas don't look that extreme. I guess no-one can really say what that means exactly - is it good, is it bad? Everything you do seems to change the structure of your brain in some way (like reading a novel [1]), so it's really hard to tell whether this is 'good' or 'bad'. P.S.: It's a bit annoying that Internet discussions about publications nowadays immediately just scream 'sample size!' without looking at the stats themselves. [1] http://www.theatlantic.com/education/archive/2014/01/study-reading-a-novel-changes-your-brain/282952/ http://www.theatlantic.com/education/archive/2014/01/study-r...
- ASneakyFox 12y ago
  Any time stats are used as "evidence" then you know its bs. You can just keep picking variables until you got a chart you want.

diminoten 12y ago

It is not true that a low sample size means a high amount of variability. Depending on the people chosen, you can have a very low P value with as few as 26 or so participants. It should be more interesting to you how reactive you were to the headline of this submission, than to the results.

former_pothead 12y ago

It's not bullshit, below are similar studies: MARIJUANA USERS HAVE ABNORMAL BRAIN STRUCTURE AND POOR MEMORY - http://www.northwestern.edu/newscenter/stories/2013/12/marijuana-users-have-abnormal-brain-structure--poor-memory.html http://www.northwestern.edu/newscenter/stories/2013/12/marij... Persistent cannabis users show neuropsychological decline from childhood to midlife - http://www.pnas.org/content/early/2012/08/22/1206820109.abstract http://www.pnas.org/content/early/2012/08/22/1206820109.abst... From personal experience, I smoked recreationally from 18 to 24 and definitely felt serious, structural changes in my brain. I won't go into the details since it's anecdotal evidence, but if research like what I linked to and the OP was presented to me, I would have dropped it. People need to be aware there are consequences to your mental development if you smoke marijuana casually. Obviously the government has blown them way out of proportion, but the problems still exist.

Im_Talking 12y ago
The studies do not show causation, only correlation. And one of the studies was funded by the NIDA which will only fund studies which show harm. It is possible that the opposite is true: that people with a predisposition to mental illnesses use cannabis to self-medicate.
- former_pothead 12y ago
  Even if that were true, it would mean the general population should be assured by a medical professional that they are not predisposed to mental illnesses before they use cannabis.
  - Im_Talking 12y ago
    You misunderstood me. I am saying that cannabis is not the culprit, in fact it helps. People use cannabis to self-medicate so use will be higher in people with mental illnesses. http://www.leafscience.com/2013/12/08/marijuana-cause-schizophrenia-harvard-study-finds/ http://www.leafscience.com/2013/12/08/marijuana-cause-schizo... http://www.leafscience.com/2014/03/25/marijuanas-effect-memory-overstated-study-finds/ http://www.leafscience.com/2014/03/25/marijuanas-effect-memo... http://www.leafscience.com/2014/03/20/5-ways-cannabis-help-fight-alzheimers/ http://www.leafscience.com/2014/03/20/5-ways-cannabis-help-f...
- waps 12y ago
  This is not a valid point against medical studies, because medical studies never attempt to prove causation. They are merely showing that event A preceeds event B with correlation of 0.51 or so. The human body is so complex that controlling for every variable is simply not possible. It's not just funding either. To control for every variable you'd need more test subjects than there are humans alive. Furthermore all medical double-blind studies do indeed only show correlation (nearly always very low correlation, a successful drug will have correlation coefficients of maybe .53 If you find a drug for almost any disease that correlates with curing any disease of .7 or .8, you can start a pharma company and it'll be worth billions). Also while correlation does not imply causation, it does mean 1 of 3 things. Suppose A and B correlate. Let's take a flu medication and getting cured as an example. 1) A causes B (people who take the drug tend to get cured from the flue as a result) 2) B causes A (people who get sick, and heal by themselves tend to take the drug because they feel sick) 3) A and B are both caused by the same thing (can be many things, e.g. the medicine salesman has the flue) There have been attempts to mathematically define causation as correlation with a time offset (the one that preceeds is the cause, the one coming after is the result). This has had only limited success. That of course does not stop nearly every study outside of the pure sciences from taking such time-delayed-correlations as proof of causation. Are you really suggesting throwing out 99%+ of science over that ? ( and 4. you made a mistake and while it looks like correlation, it's not. E.g. longterm correlations in chaotic variables, like taking the .999999999999999999 correlation between mathematical descriptions of planetary orbits and concluding those planets are actually in those orbits until something large happens [1]. Yes it goes for earth too. The orbit of the earth could alter to throw the earth into the sun, or out of the solar system and there would be little or no warning. There is also no need for "large" events to cause this. Planets' movements do not follow the central limit theorem and therefore cannot be predicted with 100% certainty. The huge problem is of course, that in the real world nearly every problem exhibits chaos, for obvious reasons, not just the stock market) [1] http://en.wikipedia.org/wiki/Three-body_problem http://en.wikipedia.org/wiki/Three-body_problem

a_bonobo 12y ago

Paper: http://jn.sfn.org/press/April-16-2014-Issue/zns01614005529.pdf http://jn.sfn.org/press/April-16-2014-Issue/zns01614005529.p... The statistical treatment looks solid, good p-values and they even controlled for multiple testing with an adjusted p-value cut-off (alpha) of p < 0.0125 Funding is a bit biased: This work was supported by the National Institute on Drug Abuse (Grants 14118,026002,026104,and 027804 to H.C.B. and Grant 034093 to J.M.G.), the Office of National Drug Control Policy, Counterdrug Technology Assessment Center (Grants DABK39-03-0098 and DABK39-03-C-0098), and the National Institute of Neurological Disorders and Stroke, National Institutes of Health (Grant 052368 to A.J.B.). H.C.B. was also supported by the Warren Wright Adolescent Center at Northwestern Memorial Hospital and Northwestern University, Chicago.J.M.G. was supported by a Harvard Medical School Norman E. Zinberg Fellowship in Addiction Psychiatry Research Figure 1 has the gist, interestingly, gray matter density slightly increased with Marijuana usage. The changes weren't that extreme for the most part, but statistically significant. The L accumbens has the largest F (Table 2), indicating a larger difference in gray matter density, the other areas don't look that extreme. I guess no-one can really say what that means exactly - is it good, is it bad? Everything you do seems to change the structure of your brain in some way (like reading a novel [1]), so it's really hard to tell whether this is 'good' or 'bad'. P.S.: It's a bit annoying that Internet discussions about publications nowadays immediately just scream 'sample size!' without looking at the stats themselves. [1] http://www.theatlantic.com/education/archive/2014/01/study-reading-a-novel-changes-your-brain/282952/ http://www.theatlantic.com/education/archive/2014/01/study-r...

ASneakyFox 12y ago
Any time stats are used as "evidence" then you know its bs. You can just keep picking variables until you got a chart you want.