Stress, and the changes that cause it
Cats are territorial in a way that makes them sensitive to changes people consider trivial.
Building work, a new sofa, a visitor staying, a change in someone's working hours, and a new cat two gardens away are all common triggers. So is a change of litter or a moved food bowl.
Stress in cats rarely looks like anxiety in a dog. It looks like hiding, overgrooming, spraying, or a cat that stops using a room.
Predictability, hiding places, height and separated resources are useful starting points. The right change still depends on whether the trigger is pain, fear, conflict, frustration or something outside the home.
A cat under pressure needs more places to be, not more attention.
Anything that persists after the trigger has gone, particularly overgrooming, is worth a vet visit rather than more time.