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Yep. I've learned in the past few years
  • how most studies are sponsored by interested parties
  • and how they're not reproducible.
This makes me suspect all studies.
Also I can tell you one thing - 99% of kids have smart phones, in middle school and high school. If you don't have a smart phone, you're very different in SOME way. And to not acknowledge that is suspect.
They should compare the 1% with flip phones to the 99% with smart phones.