See also the book The Spirit Level, which shows that inequality also negatively affects those who are well-off - they become stressed about their social standing too.
This is why naive explanations of inequality that blame the poor or the envious are false.
I don't think it proves envy false as a cause. It just means envy is of a piece with status anxiety more broadly. I doubt that anyone of any historical period would be shocked by this.
The stress of falling from the current social position (for example, in the US, the risk of inability to pay medical bills or student debt) also affects people who are not envious and comfortable with their current salary and social standing. So it's not just envious people causing psychological harm to themselves, it's the unequal system that harms mostly everybody.
I think you haven't understood what I said. I know that envy is not the only form of harmful status anxiety, and that the wealthy can suffer from non-envy status anxiety. I just think that, envy or not, it's a personal problem that those people can and should get over. They're not victims. They do it to themselves.
And struggling to pay bills is a different problem from inequality per se.
This is why naive explanations of inequality that blame the poor or the envious are false.