People need to change the sheets and pillow cases and duvet covers. When some people are depressed they find these habits harder to maintain. After a while they've become deconditioned, and they're still unmotivated, and it can be hard to get back into a routine.

Sadly I know. But you already needed to wash traditional bed dressing, actually one more sheet. The task of making the bed is much simpler with duvets, at least for me: I just take the thing with both hands, shake it a little and place it all over the bed. Compare that with placing correctly the upper sheet, the blanket and the covers. It's like ten seconds vs one or two minutes.