Certain conditions, if they remain persistent and intense enough, can cause changes in brain chemistry and such to the extent that insanity can drive one to self-destruction. I had a life-threatening bout with severe clinically measurable depression that grew darker and darker over a period of months until it was interrupted - medically - following a suicide threat.

This does not mean that I was lost during that time, nor more than the prophet Elijiah who also suffered from depression to the point of seeking death.