Feb 11 (Reuters) - Instagram's leader is set to face questions in court for the first time on Wednesday about whether the Meta-owned app's design is fueling a youth mental health crisis.

Adam Mosseri, the head of Instagram, will ​testify in Los Angeles as part of a ‌trial on what plaintiffs call "social media addiction" in children and young adults. Meta CEO Mark Zuckerberg is ⁠also expected to testify in the coming weeks.

The case involves a 20-year-old woman ⁠who said she became addicted to Instagram at a young ‌age because of ‌its attention-grabbing design, according to court filings.

The outcome of her case will influence how social media companies ​respond to hundreds of similar lawsuits in ‌the U.S.

"We strongly disagree with these allegations and are confident the evidence will show our longstanding commitment to supporting young people," a ​Meta spokesperson said in a statement ​ahead of ‌Mosseri's testimony.  

The California woman said in a deposition that Instagram's "endless" scroll feature kept her on the app and contributed to her anxiety, according to ⁠court filings.

Endless scroll is a design feature where content loads continuously as ⁠the user moves down the page. The American Academy of Pediatrics said in January that the feature may make it harder for kids to "disengage from digital devices."

Mosseri is expected to be questioned on internal company documents.

The plaintiff's counsel said ⁠the records ‌show the company was aware of harms to children from ‌using Instagram. The attorneys pointed to a recent Meta study they said showed ⁠that teens facing other difficulties in their lives were the most likely to become addicted and that parents had no meaningful control.

Meta's lawyer said in court that the company's internal discussions were for the purpose of addressing problems and adding features to give users more control.

Access to social media for children has become an issue globally, with Australia in ​December becoming the first nation to prohibit use of the platforms for children younger than 16. Spain, Greece, Britain and France are among the many countries ​considering similar action.