According to the allegations, Meta and Alphabet have built services aimed at keeping children using the platforms, with personalized algorithms and an almost perpetual flow of content that demands attention.
A young woman claims that as a child she became addicted to apps like Instagram and YouTube.
The jury now finds that the companies have not sufficiently raised warning flags about the dangers of using the platforms.
According to the verdict, the woman is to be awarded $3 million in damages (28 million SEK). Meta is to pay 70 percent of the sum and Google's YouTube service the rest.
According to the AFP news agency, an additional $3 million in general damages is to be paid, distributed the same way.
Zuckerberg admitted shortcomings
When he testified in February, Meta CEO Mark Zuckerberg admitted that his company should have been faster when it comes to identifying underage users on Instagram and adjusting the service accordingly.
The trial began at the end of January in a lower court, Los Angeles Superior Court.
It is unclear whether the ruling will be appealed. A Meta spokesperson said in a statement: “We respectfully disagree with the ruling and are evaluating our legal options.”
The case could have repercussions on social media and the broader technology market.
Meta also found liable in New Mexico
It is one of several similar lawsuits this year. The trials have been called the social media industry's "big tobacco" moment, comparing them to the 1990s when tobacco companies were forced to pay billions of dollars for lying to the public about the potential harms of their products.
On Tuesday, a jury in the state of New Mexico awarded Meta the equivalent of just over SEK 3.5 billion in damages. Jurors concluded the company had concealed what it knew about the dangers of sexual exploitation of children on the platforms.
That ruling will be appealed by Meta.
