The Facebook parent company was found to have contributed to a woman's social media addiction.
A landmark court decision has found Meta and YouTube liable for child harm, forcing the owner of Facebook and Instagram into a $US3 million ($4.31 million) payout.
A jury in California found the companies were "negligent in the design or operation of their platforms".
A woman, aged 20, brought the case against the tech giant, saying her use of social media as a child addicted her to the technology and "exacerbated her mental health struggles".
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A jury handed down the decision after more than 40 hours of deliberations across nine days. Along with the victim's payout, the jury also found the two companies negligent in the design or operation of their platforms.
Meta and YouTube were found to have "acted with malice, oppression or fraud", meaning the jury will hear further evidence to decide on punitive damages.
The victim, identified only as KGM or "Kaley", said she began using YouTube at the age of 6 and Instagram at the age of 9.
She described being on social media "all day long", with her lawyers arguing they had features designed to "hook" young users, such as the "infinite" nature of feeds.
Meta consistently argued that Kaley had struggled with her mental health separate from her social media use, often pointing to her turbulent home life.
Meta also said "not one of her therapists identified social media as the cause" of her mental health issues in a statement following closing arguments.
YouTube argued it was not a form of social media, but rather a video platform akin to television, and pointed to her declining use of the platform as she got older.
It was determined that Meta and YouTube knew that the design of their platforms was dangerous or was likely to be dangerous when used by a minor. The jurors also said the platforms failed to adequately warn of the danger, which further contributed to the plaintiff's harm.
Meta and Google-owned YouTube were the two remaining defendants in the case after TikTok and Snap each settled before the trial began.
- Reported with Associated Press
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