A jury in Los Angeles has delivered a significant verdict in favor of a 20-year-old woman who accused Meta and YouTube of fostering an addiction to social media during her childhood.

The panel concluded that Meta — parent company of Instagram, Facebook and WhatsApp — and Google, which owns YouTube, deliberately engineered platforms that contributed to harm to the plaintiff’s mental health.

The plaintiff, identified as Kaley, was awarded $6 million (£4.5 million) in damages, a decision that could influence hundreds of comparable lawsuits currently moving through courts across the United States.

Both companies pushed back against the ruling and indicated plans to appeal. Meta said: "Teen mental health is profoundly complex and cannot be linked to a single app.

"We will continue to defend ourselves vigorously as every case is different, and we remain confident in our record of protecting teens online."

A spokesperson for Google said: "This case misunderstands YouTube, which is a responsibly built streaming platform, not a social media site."

Jurors allocated $3 million in compensatory damages and an additional $3 million in punitive damages after determining the companies "acted with malice, oppression, or fraud" in managing their platforms.

Under the verdict, Meta is responsible for 70% of the damages, while Google will cover the remaining 30%.

Outside the courthouse Wednesday, parents who say their children were similarly harmed — though not part of the lawsuit — gathered throughout the five-week trial to show support.

Following the decision, some parents, including Amy Neville, were seen celebrating and embracing others awaiting the outcome.

The California verdict follows closely on the heels of a separate ruling in New Mexico, where a jury found Meta liable for exposing children to sexual content and predators through its platforms.

Mike Proulx, a research director at advisory firm Forrester, said the consecutive rulings signal a "breaking point" in public attitudes toward social media companies.

In recent months, governments including Australia have enacted measures restricting children’s access to social media. In the United Kingdom, officials are testing a pilot program examining a potential ban for users under 16.

"Negative sentiment toward social media has been building for years, and now it's finally boiled over," Proulx said.

During testimony in February, Meta CEO Mark Zuckerberg pointed to company policies barring users under 13 from its platforms.

When confronted with internal documents indicating younger children were still using the services, Zuckerberg said he "always wished" for faster progress to identify users under 13. He insisted the company had reached the "right place over time".

Although Google was named as a defendant, much of the trial centered on Instagram and Meta’s practices.

Snap and TikTok were initially included in the case but reached confidential settlements with Kaley before the trial began.

Attorneys for Kaley argued that Meta and YouTube created "addiction machines" and failed to adequately prevent underage users from accessing their platforms.

Kaley testified that she began using Instagram at age nine and YouTube at age six, encountering no barriers tied to her age.

"I stopped engaging with family because I was spending all my time on social media," Kaley said during her testimony.

She told jurors she began experiencing anxiety and depression at age 10, conditions she was later formally diagnosed with by a therapist.

Kaley also described developing an intense focus on her appearance, frequently using Instagram filters that altered her features — shrinking her nose and enlarging her eyes — soon after joining the platform.

She has since been diagnosed with body dysmorphia, a condition that distorts a person’s perception of their appearance.

Her legal team contended that features such as infinite scrolling were intentionally designed to keep users engaged.

They also argued that Meta’s growth strategy targeted younger audiences, citing testimony from experts and former executives who said younger users were more likely to remain long-term.

When Kaley’s attorneys highlighted that she once spent 16 hours in a single day on Instagram, Instagram head Adam Mosseri rejected the idea that it demonstrated addiction.

Instead, he called a teenager spending most hours of the day on Instagram "problematic".

Kaley’s lawyers said Wednesday that the outcome "sends an unmistakable message that no company is above accountability when it comes to our children."

Another lawsuit alleging harm to children from social media platforms is scheduled to begin in June in federal court in California.