LOS ANGELES, Feb 11 (Reuters) - The top executive at Meta Platforms' Instagram defended the social media platform's choices around features that some company insiders called harmful to young users, at a trial on claims the app helped fuel a youth mental-health crisis.

Adam Mosseri, the head of Instagram, testified 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.

A California woman who began using Instagram at age 9 is suing Meta and Google's YouTube, saying the companies sought to profit ⁠by hooking young children on their services despite knowing social media could harm their mental health. She alleges the platforms contributed ⁠to her depression and body dysmorphia.

In 2019, Mosseri and others at Instagram were discussing whether to lift ‌a ban on photo filters ‌that mimicked the effects of plastic surgery, according to emails shown in court.

Instagram teams working on policy, communications and well-being preferred to keep the ban in place while gathering ​more data on potential harms to teen girls.

"We would - rightly - be accused ‌of putting growth over responsibility," if the company lifted the ban, said Nick Clegg, who was then Meta's vice president of global affairs, according to emails shown in court.

Mosseri and Zuckerberg preferred to reverse the ban ​but remove the filters from the app's recommendation section, an option ​described in emails ‌as presenting "a notable well-being risk" but having a lower impact on user growth.

"I was trying to balance all the different considerations," Mosseri said in court, adding that he agreed with the ultimate decision to allow face-altering filters without highlighting ⁠them for users, but prohibit filters that overtly promoted plastic surgery.

"Our policies, like our products, evolve all the time. We ⁠try to focus on the most important issues," he said.

'MOVE FAST AND BREAK THINGS'

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.

In the U.S., Meta, YouTube and other social media platforms face a wave of ⁠litigation from families, ‌school districts and state attorneys general.

For the Los Angeles jury to find the companies liable, ‌they will have to find that Meta and YouTube were negligent in designing or operating the platforms, and that their products were a ⁠substantial factor in harms to the woman's mental health.

Several parents who say social media platforms led to their children's deaths sat in the front row of the courtroom audience. 

Victoria Hinks, whose daughter died by suicide at age 16, said their children had been "collateral damage" to Silicon Valley's "move fast and break things" culture. 

"Our children were the first guinea pigs," she told reporters outside the courthouse.

"Move fast and break things," the company's early motto coined by Zuckerberg, is no longer appropriate, Mosseri said in his testimony.

The case is a key test of a U.S. law that protects  online platforms from liability for ​user-created content, which has long shielded social media companies from lawsuits. The outcome of the case will influence how the companies respond to hundreds of similar lawsuits in the U.S.

Meta's lawyers cited the law in objecting to some evidence presented in court. The company could raise the ​issue on appeal if it loses at trial.

The trial is ‌scheduled to continue on Friday.