A US jury has found that Meta Platforms and Google must compensate a young woman who claimed prolonged exposure to their platforms contributed to serious mental health issues, marking a significant moment in a growing wave of litigation against major technology firms.

The decision, delivered in Los Angeles after nine days of deliberation, centred on a 20-year-old plaintiff who argued that years of using services such as Instagram and YouTube led to anxiety, depression and body image concerns. Jurors concluded that both companies were negligent in how their platforms were designed and operated, and that they failed to adequately warn younger users about potential risks.

The panel voted 10 to 2 in favour of holding both companies responsible. Meta was ordered to pay A$6.4 million, while Google was told to pay A$2.7 million. In each case, half of the amount was awarded as compensation for losses such as therapy costs, while the remainder was allocated as punitive damages intended to penalise the companies and deter similar conduct.

Although the sums are modest relative to the size of the companies, legal observers say the ruling could have far-reaching implications. Thousands of similar cases are already moving through US courts, many of them brought by children, teenagers and young adults or their families. The claims range from psychological harm to physical impairment and suicide.

Eric Goldman, a law professor at Santa Clara University, said the outcome reflects growing concern among juries about the influence of digital platforms on younger users. He noted that jurors appear increasingly willing to assign substantial financial penalties in such cases.

The lawsuit did not focus on specific posts or videos shared on the platforms, which are typically protected under US law. Instead, it targeted the features built into the services, including notifications, likes, autoplay videos, infinite scrolling and filters that alter appearance. Lawyers for the plaintiff argued these elements were deliberately designed to keep users engaged for as long as possible, likening the experience to gambling systems that trigger repeated dopamine responses.

During the trial, jurors heard evidence from senior executives including Meta chief executive Mark Zuckerberg and Instagram head Adam Mosseri, as well as mental health specialists. The plaintiff also testified about her experiences, stating that she began watching YouTube at the age of six and started using Instagram at nine.

Her legal team argued that such early and sustained exposure played a key role in her struggles. They said the verdict should send a clear signal that companies can be held accountable for designing products that may harm younger audiences.

Meta and Google both rejected the findings and indicated they plan to challenge the decision. A spokesperson for Meta said the company is reviewing its legal options, while Google confirmed it intends to appeal. Google also maintained that YouTube should not be considered a social media platform in the same way as services such as Instagram.

Lawyers for the companies argued that other factors contributed to the plaintiff’s mental health difficulties, including family issues, school challenges and bullying. They also pointed to medical records suggesting that her use of the platforms was not consistently harmful and, in some cases, provided positive experiences such as creative expression and relaxation.

The case is seen as an early test of a broader legal strategy that shifts attention away from user-generated content and towards the design of digital platforms themselves. Similar lawsuits have been filed against other companies including Snap and TikTok, both of which reached confidential settlements with the plaintiff before the trial began.

Beyond individual cases, technology firms are also facing legal action from around three dozen US states and more than 1,000 school districts. These cases allege that social media platforms contribute to widespread harm among young people and could expose companies to billions of dollars in damages, as well as pressure to change how their services operate.

The Los Angeles ruling comes just days after another setback for Meta, when a separate jury in New Mexico found that the company had misled teenagers about the safety of its platforms. In that case, civil penalties totalled A$573 million.

Members of the Los Angeles jury later said the volume and complexity of evidence contributed to the length of their deliberations. They also acknowledged the challenge of setting aside personal views about social media while reaching a verdict based solely on the facts presented in court.

For now, the case highlights a growing legal and societal debate about the responsibilities of technology companies and the long-term effects of digital platforms on younger users.