Meta Platforms and Alphabet’s Google must pay damages to a 20-year-old woman who said her addiction to social media caused her mental health struggles, a jury concluded in a landmark decision that could signal hefty risks for the companies as they fight thousands of similar claims.

Wednesday’s verdict in Los Angeles on the ninth day of jury deliberations shows the difficulty of ascribing how much social media is to blame for youths suffering varying degrees of distress. But it also underscores the potential multibillion-dollar exposure from lawsuits which claim that Instagram, YouTube and other platforms are intentionally designed to addict young users without regard for their well-being.

Two other bellwether cases are scheduled to go to trial in California state court this year. Defeats for the companies could spur settlement negotiations — possibly leading to a broad agreement akin to the deals that tarnished the tobacco and opioid industries.