> she's not an expert on mental health. She might be right, she might be wrong, but she isn't a source of truth.

It's FB but for the purpose of studying effects of social media on mental health it should suffice:

https://www.wsj.com/articles/facebook-knows-instagram-is-tox...

https://www.theguardian.com/technology/2021/sep/14/facebook-...

https://www.businessinsider.com/facebook-internal-report-sho...

https://hsph.harvard.edu/news/how-social-medias-toxic-conten...