Recasts with details from therapist's daylong testimony

By Jody Godoy and Steve Gorman

LOS ANGELES, Feb 25 (Reuters) - The former psychotherapist of a California woman suing Meta's META.O Instagram and Alphabet's GOOGL.O YouTube, claiming a childhood addiction to the platforms damaged her mental health, testified on Tuesday that adolescent social media usage was a contributing factor.

Victoria Burke, the licensed therapist, appeared as a witness in a landmark civil trial in Los Angeles County Superior Court testing whether Big Tech can be held liable for the design of apps widely blamed for fueling a mental health crisis among young people.

Burke was called by lawyers for the plaintiff, known in court only as Kaley G.M., to set the stage for the next phase of the trial exploring whether and how Kaley's engagement with social media as a child affected her wellbeing.

Kaley is expected to take the stand on Thursday once Burke completes her testimony.

The case is part of a broader global backlash against social media companies over alleged harms to children and teens. Australia has banned under-16s from such platforms, and other countries are considering similar restrictions. The tech firms deny the allegations and say users must be at least 13 to register.

Burke was working as a therapy trainee for a school district when she diagnosed and treated then 13-year-old Kaley for several months in 2019.

She told jurors she initially diagnosed Kaley as suffering from generalized anxiety disorder, but later revised the diagnosis to social phobia and body dysmorphic disorder.

Burke drew no conclusions as to whether social media had directly caused Kaley's adolescent struggles with fear of social rejection and peer judgment, or her worries over perceived flaws in her physical appearance.

But under cross-examination, Burke testified that she believed Kaley's social media experience was a "contributing factor" in her mental issues.

The therapist said Kaley often complained about online "bullying" by peers, and recalled at least one instance in which the girl told her she had "deleted" herself from a social media page, only to return later.

SOCIAL MEDIA USE AT AGE 6

Burke also acknowledged that Kaley's social media usage was not altogether negative, recalling that Kaley said she enjoyed creating video "art" to post online, though she became frustrated when others took credit for her work.

According to her lawsuit, Kaley began using YouTube when she was 6 and Instagram at age 9, and says the platforms contributed to psychiatric disorders, including depression and body dysmorphia.

Her lawyers have cast their client as a victim of deliberate designs and business models that sought to profit by hooking young children on advertising-supported online services despite knowing the risks to their mental health,

The beginning of the trial focused on what the companies knew about how social media affects children, and their business strategies related to younger users. Meta CEO Mark Zuckerberg testified that the company discussed but never launched products for children.

To win the case, Kaley's lawyers must show that the way the companies designed or operated the platforms was a substantial factor in causing or worsening her mental health issues.

QUESTIONS OF HOME LIFE

Kaley's health records show a history of verbal and physical abuse and a fraught relationship with her parents, who divorced when she was three, Meta's lawyer said in opening statements. Kaley's mother is expected to give evidence following her daughter's testimony.

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 allows for endless scrolling were designed to keep users on the platforms, 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 YouTube attorney in court cited records that showed Kaley's 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.

Burke said she never assessed the average duration of Kaley's daily social media usage. On Wednesday, she testified the notion of social media addiction had yet to emerge as a widely recognized phenomenon in her field, and was still not listed as a diagnosis in the latest edition of the Diagnostic and Statistical Manual, the key text for U.S. mental health professionals.

(Reporting by Jody Godoy in New York and Steve Gorman in Los Angeles; Additional reporting by Courtney Rozen in Washington; Editing by Aurora Ellis and Kate Mayberry)

((jody.godoy@tr.com))