a possible rebuttal to " The long-term effects of cannabis on your brain " from the Link you provided, I found this :
https://www.medicalnewstoday.com/articles/320895.php?iacp
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Alcohol 'more damaging to brain health than marijuana'
Published Monday 12 February 2018
By
Honor Whiteman
Fact checked by Jasmin Collier
With marijuana legalization on the rise, an increasing number of studies are exploring the drug's potential harms and benefits. However, a new study suggests that when it comes to brain health, alcohol is more damaging.
Researchers say that alcohol causes more damage to the brain than marijuana does.
Scientists at the University of Colorado Boulder conducted a review of existing imaging data that looked at the effects of alcohol and marijuana, or cannabis, on the brain.
Their findings linked alcohol consumption with long-term changes to the structure of white matter and gray matter in the brain.
The use of marijuana, however, seemed to have no significant long-term effects on brain structure.
Study leader Rachel Thayer, of the Department of Psychology and Neuroscience at the University of Colorado Boulder, and colleagues recently reported their
results* in the journal
Addiction. *
Marijuana vs. alcohol: Which is worse?
For this latest study, Thayer and colleagues sought to learn more about how marijuana use affects the brain.
Study co-author Kent Hutchison, also of the Department of Psychology and Neuroscience, notes that to date, studies that have investigated this association have produced mixed results.
"When you look at these studies going back years," he explains, "you see that one study will report that marijuana use is related to a reduction in the volume of the hippocampus. The next study then comes around, and they say that marijuana use is related to changes in the cerebellum [...]."
"The point is that there's no consistency across all of these studies in terms of the actual brain structures."
With the aim of closing the gap on this inconsistency, the researchers conducted a new analysis on existing brain imaging data. They looked at how marijuana use affects white matter and gray matter in the brain, and how its effects compare with another "drug" that we have become so accustomed to: alcohol.
Gray matter is the tissue on the brain's surface that primarily consists of nerve cell bodies.
White matter is the deeper brain tissue that contains myelinated nerve fibers, which are branches protruding from nerve cells that transmit electrical impulses to other cells and tissues.
The team notes that any reduction in the size of white or gray matter or a loss in their integrity can lead to impairments in brain functioning.
"With alcohol, we've known it's bad for the brain for decades," notes Hutchison. "But for cannabis, we know so little."
Marijuana use had no impact
The study included the brain images of 853 adults who were aged between 18 and 55 years and 439 teenagers between the ages of 14 and 18. All participants varied in their use of alcohol and marijuana.
The researchers found that alcohol use — particularly in adults who had been drinking for many years — was associated with a reduction in gray matter volume, as well as a reduction in the integrity of white matter.
Marijuana use, however, appeared to have no impact on the structure of gray or white matter in either teenagers or adults.
Based on these findings, the researchers believe that drinking alcohol is likely to be much more harmful to brain health than using marijuana.
"[...] while marijuana may also have some negative consequences, it definitely is nowhere near the negative consequences of alcohol." - Kent Hutchison
When it comes to the possible benefits of marijuana use, however, Thayer and her team note that the jury is still out, and further research is needed to reach some conclusions. "
https://www.medicalnewstoday.com/articles/320895.php?iacp
results* in the journal
Addiction. * :
https://onlinelibrary.wiley.com/doi/abs/10.1111/add.13923
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Abstract
Background and Aims
Chronic alcohol use is associated with lower gray matter volume, and we reported recently that alcohol use showed negative associations with widespread gray matter (GM) volume even among young adults. The current study aimed to test the strength of association between (1) alcohol use and GM volume; (2) alcohol use and white matter (WM) integrity; (3) cannabis use and GM volume; and (4) cannabis use and WM integrity among adults and adolescents.
Design and Setting
General linear models within large pooled cross‐sectional samples of adolescents and adults who had participated in studies collecting substance use and neuroimaging data in the southwestern United States.
Participants
The current analysis included adults aged 18–55 years (
n = 853) and adolescents aged 14–18 years (
n = 439) with a range of alcohol and cannabis use.
Measurements
The dependent variable was GM volume or WM integrity, with key predictors of alcohol use [Alcohol Use Disorders Identification Test (AUDIT) score] and cannabis use (past 30‐day use).
Findings
Alcohol use showed large clusters of negative associations (
ηp2 = 0.028–0.145,
P < 0.001) with GM volume among adults and to a lesser extent (one cluster;
ηp2 = 0.070,
P < 0.05) among adolescents. Large clusters showed significant associations (
ηp2 = 0.050–0.124,
P < 0.001) of higher alcohol use with poorer WM integrity, whereas adolescents showed no significant associations between alcohol use and WM. No associations were observed between structural measures and past 30‐day cannabis use in adults or adolescents.
Conclusions
Alcohol use severity is associated with widespread lower gray matter volume and white matter integrity in adults, and with lower gray matter volume in adolescents. "
https://onlinelibrary.wiley.com/doi/abs/10.1111/add.13923