What an interesting question!
Cats are solitary survivors who generally manage being alone much better than dogs or people do.
Nevertheless, because they have evolved to avoid being noticed by predators, we probably miss their signs of anxiety just like we can overlook their subtle signs of sickness.
Around their favourite person, kitty will be more confident to explore, whereas around strangers, kitty is more likely to be vigilant and may hide. And when alone, kitty spends more time sleeping.
We don’t know how much of this is affected by how well their environment meets their needs, though. Are they as confident when they don’t have a lookout or know that they can “disappear” should they wish to?
When a suitcase, or coffee mug and keys appear, or when kitty is left alone, signs that he/she is experiencing separation anxiety include:
Quite a wide range of responses, isn’t it?
Providing your cat with predictable one-on-one time can help. But remember, these could also be signs of physical sickness, so it’s good to look for these clues for your own peace of mind and, above all, your cat!
Anything that causes stress can result in illness:
Stress can cause idiopathic cystitis > cystitis causes pain > pain causes stress
What a vicious cycle! So, look for these signs and, if you see any of them, talk with your veterinarian. We are always happy to help!