Firstly, I don't think we can prove any direct link between social media and mental health issues which would stand in a court and allow anyone to be prosecuted for causing a mental health issue! Also, mental health problems often don't have one singular cause, this is simplifying the issue greatly. An otherwise mentally healthy person would not become mentally ill due to simply watching a vlogger or using social media a few times. And, say we WERE triggered by social media or a vlogger. Are the social media companies, or the vlogger - who didn't MAKE me watch them, who didn't come into contact with me, who don't even know I exist - responsible that I personally made the decision to watch/use them and presumably continue to do so even after my mental health began to deline?
People who are prone to or vulnerable to mental illness already can be triggered by literally anything and starting to try and not only pinpoint but also prosecute this would be impossible and just... Crazy!
Once you open those floodgates where would it end? Schools, colleges and universities being prosecuted for stressing out students with exams and essay deadlines, and therefore triggering mental health issues? Neighbours having disputes being prosecuted for giving each other mental health issues? People being locked up for breaking up with a partner and triggering their mental health issues?
I suffer from anxiety, one way it manifests is as severe health anxiety, and I can easily be triggered by posts on Mumsnet which don't come with a warning in the title. Could I prosecute Mumsnet? Actually what sets me off more than anything is well-meaning awareness adverts from the NHS and charities. Would I be able to prosecute them? That would cost the NHS a fortune as I'm sure I'm not the only one.
I also can be triggered by newspapers and the news - seeing certain stories can set me off easily and I can be quite unwell for months. Could I prosecute the newspaper that I chose to read? Or the radio that I chose to listen to? Etc? This is just unrealistic. Literally all media sources would have to close down.
Also, how could we possibly prove what caused a mental health issue? Pinpoint the one, single route cause? The court cases would be a disaster.
What about people who are prone to mental health issues (for example, some conditions are not hereditary but there's a higher chance of someone suffering if a parents or family members have). Would these people all have to be exempt from getting anyone punished as nobody could be fully to blame?
What if I'm left feeling triggered by a situation I put myself in? Could it be argued that actually, it wasn't the business that triggered the problem but rather it was ME who caused it, as I, as a mentally healthy adult individual who is capable of making my own decisions, decided to do something which ultimately was bad for my mental health? Why should other people be prosecuted for that?
I'm just trying to illustrate that this would be not only pretty impossible, but it would also be a very dangerous route for society to go down, floodgate-wise.