After days of deliberation, a jury in a Los Angeles court on Wednesday said that Meta and YouTube were negligent in a landmark trial where a 20-year-old woman said that her use of social media in her teens addicted her to the platforms and made her depression worse.

Meta and YouTube were ordered to pay a combined $6 million in damages to the plaintiff, identified as K.G.M. Meta and YouTube said they will appeal.

“The era of Big Tech invincibility is over – this ruling is an earthquake that shakes Big Tech’s predatory business model to its core,” Sacha Haworth, executive director of The Tech Oversight Project, said in a statement. “New evidence and testimony have pulled back the curtain and validated the harms young people and parents have been telling the world about for years. These products were purposefully designed to harm, addict millions of young people, and lead to lifelong mental health consequences.”

The complaint argued that Instagram, Facebook, YouTube, TikTok and Snapchat “rewired how our kids think, feel, and behave,” by knowingly designing addictive products that exposed children to harm. Snap and TikTok settled with the plaintiff before the trial began.

The verdict of the trial could serve as a “bellwether” for similar cases in the future, in the U.S. and elsewhere, with many analysts likening it to the cases against Big Tobacco which forced companies to change their business practices.