The reason you look at suicide and violent crime is that they're clear indicators. Diagnosis of mental illness is not: definitions, diagnostic techniques, and access to diagnoses have changed radically over the last 100 years. It's similar (though less rigorous, for several reasons) to homicide being the gold standard crime statistic.
I'm not making a claim that mental health doesn't matter if it doesn't result in suicide or incarceration. I'm saying: those are two sets of numbers you can find going back to the intervention (the sanitization of fairy tales) and trace since then.
The story those numbers tells doesn't match the just-so story the comment provides. Maybe there's more going on than those numbers represents! But I think you'll have a tough time supporting that argument with facts. For instance: the claim was made across the thread that suicide levels were artificially suppressed in 1900 because of religious norms, which works against the story; moreover: you can see in the actual charts what suicide tracks with (it's not a smooth line).