QUESTION: I'm writing for a character I'd like to classify as having some sort of disorder, but I’m not sure what would fit with circumstances properly or how to reflect that in speech or thought patterns, and interpersonal relationships with strangers, close friends and those of the opposite sex.ANSWER: Sounds to me like a delusional disorder, probably grandiose delusions with some paranoia, would be your best bet.
The character is female, twenties, and would need to have some paranoia and believe she is on an extremely important mission. Other symptoms I could squeeze in could be hallucinations, easy to distract, or things like that. If possible I’d like to keep her thought patterns fairly logical but if no disorder fits I'm up to the challenge. I'd also like to leave the possibility open that she may not be as "disordered" as she appears.
I'll explain better what that means in a minute, but the good news is that people with delusional disorders may seem totally normal to other people until and unless the delusion is triggered. So she might seem totally normal to people she encounters in casual day-to-day life, like the supermarket checkout person and even people she works with if their interactions are extremely shallow.
A delusion is a not-based-in-reality idea that you can't get the person to shake regardless of evidence. Many (all?) really die-hard conspiracy fanatics are delusional.
You didn't mention whether her important mission is something that could really happen. For example, if she believed that the President had tapped her as a civilian to go on some mission for the CIA, that's possible in the world as we know it. Ridiculously unlikely, of course, but possible. Possible = "nonbizarre delusion."
If she believed, by contrast, that aliens were beaming a mission into her brain using an implant they put there when they abducted her as a child (or whatever), that's not possible in the world as we know it. Impossible = "bizarre delusion."
Technically, if someone has bizarre delusions, they automatically get a schizophrenia diagnosis. For your character, it would be paranoid schizophrenia with prominent grandiose delusions. Grandiose delusions, according to psychology's diagnostic manual, are "delusions of inflated worth, power, knowledge, identity, or special relationship to a deity or famous person."
Even with a paranoid schizophrenia diagnosis, you still wouldn't have to add a bunch of unnecessary symptoms -- the strange ideas (delusions) could be her key symptom.
Someone with a fixed delusion is going to believe they're right and others are wrong, but your character could wonder once in a while if she's losing it, as long as she always decides she isn't. Someone with a delusion is also going to see "proof" in innocuous things that others might never even see as significant. And she will definitely become aware that others think she is unwell, and that will be uncomfortable. She might even start to buy the idea that she is, but the beliefs/delusions need to persist.
I think you probably need to write her ideas and the "proof" she sees as a little over the top from time to time, so the reader wonders if she's not just mentally ill. At the same time, the evidence could be convincing to her -- and perhaps to the reader from time to time, too. You could also play with using her as an unreliable narrator. In a lot of ways that's all mental illness is -- something that keeps someone from being a reliable narrator on life as most people see it. :)
Hope that's helpful!
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