Not absolutely certain. It's an impression I've picked up from mass media accounts, and it seems reasonable to me.

It would be good to have both more science and more personal accounts.

Thanks for asking.

My mom is a psychiatrist, and she's given an explanation basically equivalent to that one - that people with very severe depression don't have the "energy" to do anything at all, including taking action to kill themselves, and that when they start taking medication, they get their energy back and are able to act on their plans.