The California case was the first trial of thousands of consolidated lawsuits filed by teenagers, school districts and state attorneys general against Meta, YouTube, TikTok and Snap. More trials are scheduled for this year. TikTok and Snap settled the first case but are on the hook for the others.

Omri Ben-Shahar, a law professor at the University of Chicago, said the verdicts reflect an expansive view on tech companies’ liability for their products.

“What is new is the addiction element,” he said. “That could create a very broad liability. The notion of addiction, there is something very abstract about it.”