The lawsuit was filed by Thomas because the 46-year-old actor "intentionally maligned and defamed him, and caused him to be blacklisted in the show business community".
In his legal action, the Amityville Horror actor accuses ex-wife Mary Jo Slater and the Mr. Robot star of slander, libel, defamation of character, intentional interference with prospective economic advantage, and invasion of privacy, as well as intentional infliction of emotional distress.
And Thomas also noted Christian - who had made the comments last July - didn't have the "medical credentials" to correctly diagnose him with any condition.
Speaking to director Lars Von Trier for Interview magazine, Christian discussed his estrangement from his father and said the elder actor had "always had trouble" working with other people.
He said: "He's a manic-depressive schizophrenic. He's always had trouble - he was a fantastic actor and extraordinarily charismatic and very, very good looking, but he had a really difficult time working with directors, collaborating with people."