Researchers tracked 1,522 teenagers for a year using their phones' own sensors. More hours on Snapchat, TikTok, and Instagram lined up with more drinking, vaping, and cannabis use. More hours on YouTube didn't, if anything the opposite.

I've read plenty of "screen time is bad for kids" studies that lump every app into one bucket. This one didn't. It split six apps apart and found they don't behave the same way at all, which is the part that actually made me stop and read the methods section twice.

What they did

The data comes from the ABCD study (Adolescent Brain Cognitive Development study), a large, nationally diverse US cohort that has been following kids since childhood. This analysis used the first wave where the study had sensor-based phone data, meaning actual measured hours per app, not a teen's guess at how much they used TikTok that week.

  • Baseline sample: 1,522 kids, ages 13 to 16
  • Follow-up one year later: 1,121 of them
  • Apps measured: Snapchat, TikTok, Instagram, YouTube, and two others
  • Substances tracked: alcohol, nicotine/tobacco, and cannabis

The first pass compared app hours and substance use at the same point in time. The second pass followed teens who already reported using a substance at baseline, checking whether their app hours predicted use a year later.

What they found

  • Hours on Snapchat, TikTok, and Instagram were positively associated with alcohol, nicotine, and cannabis use at baseline, across multiple measures.
  • Hours on YouTube ran the other way. More YouTube time was linked to less substance use, not more.
  • The pattern held up in the one-year follow-up among teens who were already using at baseline, so it wasn't just a same-day coincidence.

What's interesting is that this isn't "social media, generically, is bad." One of the biggest platforms in a teen's daily rotation showed a protective pattern, while three others didn't.

What it means

The authors' read: it's about content and format, not just time spent staring at a phone. Snapchat and TikTok run on short, disappearing, personal clips - exactly where a party story or a vape trick gets shared casually and vanishes before anyone catches it. YouTube leans long-form: tutorials, gaming, commentary. A different content mix, and maybe a different reason kids open the app in the first place.

I want to be careful here, because the study is honest about its limits. Part of it is cross-sectional, so a teen prone to risk-taking might simply prefer Snapchat over YouTube, rather than Snapchat causing the risk-taking. And self-reported substance use at that age always carries some noise. But the fact that the association survived a full year, among kids already using, makes we-just-caught-a-random-blip a less likely explanation.

What I take from this as someone who thinks about drinking behavior for a living: exposure adds up quietly. Nobody decides to normalize a drink or a hit after watching one clip. It's the accumulated drip of "everyone's doing this and it looks fine" that resets what feels normal, for teens now and, honestly, for the adults who grew up on the same feeds. Worth remembering the next time a night out feels like it's following someone else's script instead of your own.

Source: Addictive Behaviors, DOI