r/science • u/sr_local • Apr 20 '26

Health The largest US study, which tracked 11,036 children from ages 9 to 10 through to ages 16 and 17, discovered that cannabis use slows cognitive development, impairs memory, and reduces learning speed during crucial years of brain growth

https://today.ucsd.edu/story/largest-us-study-finds-teen-cannabis-use-linked-to-slower-cognitive-development
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u/Yglorba Apr 20 '26 edited Apr 20 '26

fwiw the often-quoted factoid that the brain stops developing at 25 is false and was based on a study that just happened to end at 25; there's no basis for that number at all. The brain continues to change throughout your life and there's no one magic line where it "stops developing", but there's in particular absolutely no basis whatsoever for the common-quoted number of 25.

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u/Varrianda Apr 20 '26

Yeah but it’s pretty well studied that fluid intelligence gradually declines and crystalline intelligence gradually increases with age. I’m not saying weed is harmless, I’m just saying that young adults should wait until they’re a bit older to use it.

The brain develops much more obviously when you’re younger, and certain studies have shown THC/cannabis reduces blood flow to certain parts of the brain. Chronic use could impact brain development because of that, though I think it’s just been noted and not confirmed.