Chinese researchers analyzed college students. They gave them videos they liked and took brain scans.
It showed certain sections of the brain associated with addiction were lit up.
"TikTok clips are designed to continue to engage attention and to turn away is very difficult because it's like, after you've been -- say -- fasting for three days, then there's a sumptuous meal in front of you, it's hard for anybody to pull back," Dr. Michael Manos of Cleveland Clinic Children's said.
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The social media app floods users with videos they like, keeping them glued for hours.
The study said about 5.9% of TikTok users might have significant problematic use.
Experts say kids have a hard time knowing when to shut it off because the brain's prefrontal cortex that targets impulse control and decision-making does not fully develop until age 25.
"In addition to enabling parents to control screen time as part of our Family Pairing features, TikTok limits evening push notifications and proactively surfaces in-feed reminders to take breaks from our app," TikTok said in a statement.
Health experts say parents can take action and limit the screen time their kids spend on TikTok and other social media apps.