Meta shut down internal research into the mental health effects of Facebook and Instagram after finding causal evidence that its products harmed users mental health, according to unredacted filings in a class action by US school districts against Meta and other social media platforms.

In a 2020 research project code-named Project Mercury, Meta scientists worked with survey firm Nielsen to gauge the effect of deactivating Facebook and Instagram, according to Meta documents obtained via discovery.

To the company’s disappointment, people who stopped using Facebook for a week reported lower feelings of depression, anxiety, loneliness and social comparison, internal documents said. Rather than publishing those findings or pursuing additional research, the filing states, Meta called off further work and internally declared that the negative study findings were tainted by the existing media narrative around the company.

Privately, however, staff assured Nick Clegg, Meta’s then-head of global public policy, that the conclusions of the research were valid.

The Nielsen study does show causal impact on social comparison, (unhappy face emoji), an unnamed staff researcher allegedly wrote. Another staffer worried that keeping quiet about negative findings would be akin to the tobacco industry doing research and knowing cigs were bad and then keeping that info to themselves.

Despite Meta’s own work documenting a causal link between its products and negative mental health effects, the filing alleges, Meta told Congress that it had no ability to quantify whether its products were harmful to teenage girls.

Flawed methodology

In a statement, Meta spokesman Andy Stone said the study was stopped because its methodology was flawed and that it worked diligently to improve the safety of its products. “The full record will show that for over a decade, we have listened to parents, researched issues that matter most, and made real changes to protect teens,” he said.

The allegation of Meta burying evidence of social media harms is just one of many in a late Friday filing by Motley Rice, a law firm suing Meta, Google, TikTok and Snapchat on behalf of school districts around the country. Broadly, the plaintiffs argue the companies have intentionally hidden the internally recognised risks of their products from users, parents and teachers.

TikTok, Google and Snapchat did not immediately respond to a request for comment.

A hearing regarding the filing is set for Jan 26 in northern Califo­rnia district court.

Published in Dawn, November 24th, 2025