<p><a href=“Regular pot smokers have shrunken brains, study says”>http://www.latimes.com/science/sciencenow/la-sci-sn-regular-marijuana-shrinks-brain-20141110-story.html</a></p>
<p>although they may have had the ‘shrunken brains’ before becoming pot heads. Their IQs were significantly lower also.</p>
<p>Something to post in college dorms.</p>
<p>Maybe this explains some of the NPR Serial–both Jay and The defendant who was convicted and serving a long time. </p>
<p>Or you can email it to your college kids like I just did. 
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<p>I glanced at that study. Here are the demographics:</p>
<p>“A total of 110 participants consisting of 62 nonusing controls and 48 marijuana users were recruited through fliers and media advertisement in the Albuquerque, NM, metro area. We previously presented results on subgroups of these participants (8, 23, 24). Written informed consent was obtained from all participants in accordance with the Institutional Review Board (IRB) of The University of New Mexico. The inclusion criteria for all of the participants were as follows: (i) English as the primary language; and (ii) no current or history of psychosis, traumatic brain injury, or neurological dis- order. Marijuana users (cannabis group) were included if they currently use marijuana regularly (at least four times per week) over the last 6 mo (con- firmed via positive THC-COOH urinalysis). Nonusing controls (control group) had no self-reported regular use of marijuana and had a negative urine drug screen at baseline.”</p>
<p>The chronic pot users (and the larger group that included more than pot) had more schooling and what looks to be statistically insignificant IQ differences. </p>
<p>My first thought was: the people who’d respond might well tend to be those worried about the effects of pot smoking. I saw that 25 of the 48 were reported as marijuana dependent. In other words, I didn’t see any effort to look or control the characteristics of those users who responded versus other users; they only needed to speak English and hadn’t been diagnosed with brain/mental issues. So for example, many mathematicians and physicists and the like smoke pot. They may not classify themselves as dependent. They may not want to participate in a study like this. Would the results show brain changes? And if they did, would we then think pot smoking has a positive effect because, look, you can see these are really smart people and their brains show pot changes? </p>
<p>It’s hard to tell what’s going with pot-related problems. Look at this: “Behavior related to marijuana use was captured by using the Marijuana Problem Survey (MPS) (27). The MPS is a 19-item mea- sure that assesses the negative psychological, social, occupational, and legal consequences of marijuana use in the last 90 d (e.g., problems with family and significant others, missing work or losing a job, feeling bad about marijuana use). Each problem is rated from 0 (“no problem”) to 2 (“serious problem”), and the number of items endorsed as 1 or 2 is summed to create an index of the total number of problems (range = 0–19). Treatment-seeking marijuana users report an average of 9–10 problems.” But the demographic summary says this: a range of 3.4 ± 4.1. Not sure what to make of a range that extends below 0. For pot users only, not other stuff, the range is 2.4 ± 2.5. Again, is that meaningful?</p>
<p>I barely looked at the statistical part, but I saw it mentions IQ as a covariate. The IQ differences were reported, for example, for the controls as 110.9 ± 11.6 and the drug users as 105.8 ± 12.2 and the pot only as 104.0 ± 1.4. So again, huh? At most, this looks like a very small relationship; the controls may have lower IQ’s than the heaviest users!</p>
<p>Lerg did a wonderful job showing what the data actually say. </p>
<p>Here’s from the researcher’s mouth for more evidence: <a href=“Here's the Real Story Behind That 'Marijuana-Changes-Your-Brain' Study”>http://mic.com/articles/87875/here-s-the-real-story-behind-that-marijuana-changes-your-brain-study</a></p>
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<p>I love when people run with headlines and don’t take the time to read. Especially when they’re using it as “evidence” that another group of people is less intelligent.</p>
<p>Your link points to a different study, Romani – but the point is still the same. The newer study (reported in the press) – and done by a different research group - is still a small sample, without randomization of subject selection, and lacks any sort of longitudinal (before/after) data – so there is no way to know whether differences observed predated the mj use. </p>
<p>Individuals have different reactions to smoking pot, and that is going to impact whether they continue to use it regularly – and that very well may be due to factors related to brain structure that might in turn make the marijuana high more enjoyable to them. So there’s a pretty high likelihood that these differences predate the marijuana use. </p>