https://www.medrxiv.org/content/10.1101/2024.02.19.24301010v...
Sometimes drug and medical device companies will gag patients with non-disparagement agreements, while letting the success stories post freely on social media to promote their product/procedure/etc.
More recent work indexed in Google Scholar: https://scholar.google.com/citations?hl=en&user=TVozLNoAAAAJ...