A California woman is set to testify in court on Wednesday about how using Meta Platforms' Instagram and Google's YouTube as a child affected her mental health, as her landmark trial in Los Angeles continues.

The plaintiff, known as Kaley G.M. in court, began using Instagram at age 9 and YouTube at age 6 and says the platforms contributed to mental health issues, including depression and body dysmorphia. The companies sought to profit by hooking young children on their services despite knowing social media could harm their mental health, her lawyers say.

The case is part of a broader global backlash against social media companies over alleged harms to children and teens. Australia has banned young users from the platforms, and other countries are considering similar curbs.

The beginning of the trial focused on what the companies knew about how social media affects kids, and their business strategies related to younger users. Now it will zoom in on the woman's claims of how the services affected her. CEO Mark Zuckerberg testified that the company discussed but never launched products for children.

To win the case, her lawyers will have to show that the way the companies designed or operated the platforms was a substantial factor in causing or worsening her mental health issues.

Her health records show a history of verbal and physical abuse and a fraught relationship with her parents, who divorced when she was 3-years-old, Meta's lawyer said in opening statements.

Her own lawyer has pointed to a recent internal study by Meta where teens with difficult life circumstances more often said they used Instagram habitually or unintentionally.

Features such as videos that autoplay and a feed that lets users endlessly scroll were designed to keep users on the platforms longer, despite evidence of harms to younger users' mental health, her lawyers allege. Meanwhile, "like" buttons catered to teenagers' need for validation while beauty filters warped their self-image, the lawyer said.

YouTube's lawyer said Kaley failed to use platform features designed to protect users from bullying, including tools to delete comments and limit time spent watching videos, according to a court filing.

The attorney in court cited records that show her average time viewing YouTube shorts was around 1 minute 14 seconds a day and her average time spent streaming YouTube videos in the past five years was around 29 minutes.