I think personal responsibility does play into these situations to some extent, but even so, that doesn't imply there should be zero regulation.

Both for crack addicts and teens using social media, they not only hurt themselves, but also hurt those around them.

The studies on teen mental health largely suggest that mostly it's not about using a lot of social media yourself, but living in an area where social media is the coin of the realm. It's the toxic culture SM generates rather than direct use that's hurting teen mental health.