The largest study yet into the effects of cannabis on the brains of 18- to 36-year-olds has found that the drug can reduce brain function during cognitive tests. The findings will help people to make an informed decision about the pros and cons of using cannabis.
Archived version: https://web.archive.org/web/20250130042220/https://newatlas.com/brain/young-adult-cannabis-brain-function/
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With the low sample size of the study, I wonder how much of that is confounding variables. I know when I’ve been at my heaviest cannabis usage, my life was falling apart and I was using it to cope with a shitload of stress — which is known to cause short-term and working memory impairments.
Then you’ve also got, say, ADHDers (diagnosed or otherwise). We’ve literally got dogshit working memory disorder and as a population we tend to love substances (on account of the underactive reward circuits in our brains).
I haven’t read the full study, but as the article says the effects lingered for 2-4 weeks, it sounds like the retesting after abstaining would eliminate confounding variables. Unless they somehow resolved the stress or ADHD at the same time.
Seems as though they didn’t retest, they only scanned people once. Scanning people is expensive and getting people to show back up for a second scan is difficult. The abstention periods are likely based on self-reports.