I worked in “the unemployment office” for years and years. A lot of people cannot handle third-shift work (overnight). From what I have read and seen, the best approach is to have a stable sleep pattern. But almost all 3rd shift workers I have dealt with switch their schedules to “normal” on weekends and time off. Who wants to be up in the middle of the night on your day off when everybody else is sleeping? I think it’s the constant switching of sleep schedules that causes the problems.
The worst are the employers who require workers to rotate shifts every couple of weeks or even more frequently. I asked one of them why and he said, “Everyone would fight to be on first shift if we didn’t make them rotate.” My idea of paying first shift workers less and third shift workers more did not compute with him.