Schizophrenia: "Do You Hear What I Hear?"
Multiple personality disorder: "We Three Queens Disoriented Are"
Dementia: "I Think I'll Be Home for Christmas"
Narcissistic: "Hark the Herald Angels Sing About Me"
Manic: "Deck the Halls and Walls and House and Lawn and Streets and Stores and Office and Town and Cars and Busses and Trucks and Trees and Fire Hydrants"
Paranoid: "Santa Claus Is Coming to Get Me"
Personality disorder: "You Better Watch Out, I'm Gonna Cry, I'm Gonna Pout, Maybe I'll Tell You"
Obsessive-compulsive disorder: "Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock, Jingle Bell, Jingle Bell, Jingle Bell Rock." (Better start again.)
Passive-aggressive personality: "On the First Day of Christmas My True Love Gave to Me (and Then Took It All Away)"
Borderline personality disorder: "Thoughts of Roasting on an Open Fire"