"The bottom of the mountain"

At WebMD, a husband writes about his wife's severe depression:

Each time she has fallen down this well, it's been triggered by some small concerns nagging her, and she starts to worry about them. It's like watching a snowball coming down a mountain -- it just gets bigger and bigger. And I can't stop it. Finally, it comes to rest at the bottom of the mountain...

Depression is taxing not only to the one that suffers it, but also to all those around the depressed: relatives and friends. Coping requires lots of love and patience. Unlike physical illness, a depressed person cannot 'think correctly.' Those around the depressed must not take it lightly.

Oh God, depression is so bad!