[varjag]

Hard to tell. Some of the people who went through GULAG system were convinced atheists. Sergey Korolev, the father of Soviet space programme. Or Dmitry Likhachev. Lev Landau who was wrecked physically yet not in spirit. And certainly thousands of less notable people we never heard about.

[mlechha]

It's not about being an atheist per se, but about believing. The others I'm sure strongly believed in something, which kept them going. Landau for example had physics to occupy him and keep him sane.

[varjag]

IMO that's not quite the same. Doing physics isn't "believing" in physics, but sure keeping yourself focused on something goes a long way.

Likhatchev deathbed words to his crying wife were "don't get so upset, it's just the matter changing its state".