Those that TRULY are depressed/ill will go through it without mentioning it to anyone, and honestly, hide whatever is bugging them so no loved ones around that person have any idea until it's too late. That was how it was with my dad. On the outside he was still that happy-go-lucky jolly man, but internally, he had secretly been plotting his death for some 6 months. We just got super lucky and found him before it was too late...