This is my cat and he is as retarded as he looks like

This dude’s name is Lexus. We adopted him 4 years ago when he was a month old and that time he was just a regular kitten. A year after he suddenly started doing stupid and/or strange things as if some day he fell awkwardly or somehow injured his head.

Here is the anamnesis:

Hanging up

When something distracts him while eating, he starts staring there with the food falling from his open mouth.

Troubled sleep

He falls from where he sleeps (might be the reason of his imbecility) and produces short meow sound as he hits the ground.

Brain fails

When he sees something on the wall or ceiling higher than he can reach (a fly, for example), his tails starts convulsively twitching and he produces strange click sounds with his mouth until it disappears.

Kinky eating habits

He eats my another cat’s vomit (she is bulimic and vomits every time after meals).

Sociophobic behavior

He often hides himself in hard-to-access places for days and has a concerned or melancholic look when he appears.

He has periods of remission during which he behaves like a normal cat, plays with his toy mice and shows no signs of mental disturbance, but not for too long. Soon his bipolar affective disorder throws him back to depression and we miss him for a couple of days. I would offer him some cat antidepressants or bring him to a vet-psychiatrist, but I’m not sure if those exist.