Cassandra Complex: The Cassandra Complex is a psychological phenomenon in which an individual's accurate prediction of a crisis is ignored or dismissed.
Impostor Syndrome exists as well: The (also spelled ), sometimes called or , is a psychological phenomenon in which people are unable to internalize their accomplishments. Despite external evidence of their competence, those with the syndrome remain convinced that they are frauds and do not deserve the success they have achieved. Proof of success is dismissed as luck, timing, or as a result of deceiving others into thinking they are more intelligent and competent than they believe themselves to be.
Paranoia is also a thing, but it seems there is no specific name for a syndrome in which the sufferer is convinced that he or she is under the influence of a Cassandra-like curse, believed by no one. No matter what the individual does, they feel that they are not trusted and are regarded as treacherous, a liar, and so forth.
This means that the person with this delusion can't engage in any type of behavior, even completely innocuous activities such as shopping or reading a book, without feeling like they must be able to provide proof of their activities just in case the ever-condemning Others decide to pounce and demand an accounting of one's time.
There seems to be nothing that can be done for this mental state. Possibly more or different types of anti-psychotics? Anti-epileptics? The condition itself causes near-constant anxiety and exhaustion, along with a sense of dread and bitterness. No matter what one does, however upstanding and innocent one might be, one will forever be labeled a liar and a degenerate by one's own mind.
You might imagine that someone with this condition would just give up on bothering to do the right thing, since they will never feel like anyone believes they aren't wicked anyway, but a staunch sense of morality gets in the way. If everyone else believes you a liar, at least you can cling to the knowledge that you are NOT. Since the nature of the delusion requires you to accept it as fact, if you choose to act according to what you believe people expect of you, you no longer have any comforting truth to grab onto.
Admittedly, you wouldn't have the constant war between how people see you (according to the delusion) and what you know to be true about yourself, but turning into the creature you doggedly believe the public fancies you to be is worse than an ongoing internal civil war.
At any rate, it is illogical, troublesome, and exhausting.