Cats have emotions just like you. The only difference is that the emotions of a cat are far more important than the humans of a human being. Since cats have emotions, that means they can get depressed just like people do.
Cats can get depressed if there’s a change in their routine, an addition of a new pet or person, or just because they’re bored. The solution is to spend a ton of time and money on your cat, but before you do that, make sure your cat is really depressed and not just messing with your mind.