It's not exclusive to Olympic caliber athletes- any successful athlete-be it football, baseball, basketball, bowling, etc., to get to a level of top tier performances, when the end comes, you're left with a whole lot of nothing.
For that matter, top level scientists, researchers, academics, etc., to get to that level, you have to be singularly focused on a goal that consumes you whole.
The higher you climb in your particular field, the farther you find yourself plummeting when the end of that particular road ceases to exist. The key to success in most cases is to develop interests and friendships outside your area of expertise, away from those people and things that are hanging around solely due to your successes. The hard part is, finding those things and people because the person is so focused on the outcome they're not realizing how vital those things are until it's too late.
We are in desperate need of mental health care for all, not just olympians. We have homeless vets living on the streets facing the exact same crises of the mind that these Olympians face-the inevitability that what was your entire life is now over and coping with everyday life is an impediment.