Ayurveda has said for centuries about balancing your doshas, pitta, kapha etc. These are all related to your gut, a good gut relates to a good mind.

Google the "gut brain axis" or a "leaky gut". All this processed food, sugar, salt and other chemicals being added in like MSG, estrogen pumped into cows to fatten them etc creates a crap gut, which causes inflammation of the gut and eventually inflammation of the brain. The net effect is depression, suicidal thoughts etc. This is more prominent in some than others as the composition of their gut bacteria varies so much.