Cat meows excessively when left alone for any amount of time

Ever since we got my cat as a kitten she has hated being alone! If we leave her alone in the cat room for even 5 minutes she is throwing herself up against the door and howling. She has caused a lot of damage to our door because she excessively scratched into it during this process as well. We have to leave her in the cat room all night because if she is left alone she tears things up or chews through something. We have tried everything! But she just seems to panic when she is alone. Does anyone know what we could do to fix this?? Or soothe her in some way? Is she mental? I'm just really concerned for her.

At the risk of suggesting the obvious, could you get another cat to keep her company?

As a general rule, cats that have another cat to play with are happier and less prone to tearing things up.

I have neighbors who have a cat and a dog, and the cat gets very sulky and destructive if they take the dog with them to their vacation home and leave him alone.

We do. She is in there with our other cat every night. It keeps her occupied for a longer amount of time but alas, she continues all of the stated behavior after 20-40 minutes.