Suicide does not have stable reporting rates. It was very stigmatized in the past, and so investigators would notoriously report suicides as "unknown cause of death" if they could.
Violent crime, on the other hand, is much more correlated with things like poverty than with mental health.
I think it's quite obviously the case that there are no clear indicators about what "mental health" looked like 100 years ago and there. Any projections into the past will involve a lot of extrapolation and have all sorts of biases.
Suicide does not have stable reporting rates. It was very stigmatized in the past, and so investigators would notoriously report suicides as "unknown cause of death" if they could.
Violent crime, on the other hand, is much more correlated with things like poverty than with mental health.
I think it's quite obviously the case that there are no clear indicators about what "mental health" looked like 100 years ago and there. Any projections into the past will involve a lot of extrapolation and have all sorts of biases.