During my obsession with geneology while researching my family line, it was not uncommon to see death certificates giving cause of death as, "Death by Insanity".
One of my relatives arrived at the Poor House in Halifax, NS on the eve of Christmas. That season is known to trigger depression for some. My relative died of Insanity 3 or 4 days after checking in (or being checked in) to the Poor House.
Wtf? Were they killing mentally disturbed people?
My guess is that Death by Insanity was a euphemism for suicide. It would warrant a proper academic study.