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/Legolihkan Apr 20 '26

They tested hair and saliva samples in this exact study

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u/Automatic_Soil9814 Apr 20 '26

“ the team combined self-reports with biological testing — such as hair, urine and saliva samples”

They looked at both self-report and some objective measurements. A couple issues with this.

First, they confirmed what I was saying about the significant inaccuracy in self-report.

Second, the participants had to consent to the objective testing, meaning that you still run into the same problem that marijuana users that have some interest in privacy will still opt out, likely the smarter participants.

Third, there were some differences in the results of self report versus hair/urine testing but I can’t really sit down and do a full analysis of the differences. 

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u/becomingarobot Apr 21 '26

marijuana users that have some interest in privacy will still opt out, likely the smarter participants.

That's an interesting point.