When my atheist sister was having a double transplant - liver and kidney, she asked all her friends and relatives to think positive thoughts for her. We did, and no doubt the few with religious beliefs prayed for her. I'm sure the thought of all those people cheering her on, helped her recover, just like a sports team getting crowd support can be helped to victory.
Of course, what really saved her was medical science, not our thoughts, but our thoughts certainly helped her mental recovery.