Borderline personality disorder:

Thoughts of Roasting on an Open Fire

Dementia:

I Think I'll Be Home for Christmas

Depression:

Silent Anhedonia, Holy Anhedonia, All is Flat, All is Lonely.

Manic:

Deck the Halls and Walls and House and Lawn and Streets and Stores and Office and Town and Cars and Buses and Trucks and Trees and Fire Hydrants and…

Multiple personality disorder:

We Three Queens Disoriented Are

Narcissistic:

Hark the Herald Angels Sing About Me

Obsessive-compulsive disorder:

Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, ………(better start again)

Paranoid:

Santa Claus is Coming to Get Me.

Passive-aggressive personality:

On the First Day of Christmas My True Love Gave to Me (and then took it all away).

Personality disorder:

You Better Watch Out, I'm Gonna Cry, I'm Gonna Pout, Maybe I'll Tell You Why.

Schizophrenia:

Do You Hear What I Hear?