Wealth inequality doesn't cause this kind of despair. We have the greatest wealth inequality in history, but also the objectively best quality of life in history by most metrics (extreme poverty, hunger, starvation, death from disease, infant mortality...)

It does not matter to me if Elon Musk makes another billion dollars if I am making more as well. That does not cause "despair" to a well adjusted person.

Extreme poverty on the other hand (which has been decreasing) does cause these deaths. When people have nowhere left to go and no hope, they to turn to drugs.

Mental illness is another cause. I wonder if we should have gotten rid of asylums.