So a key part of my story is about one of my characters being mentally unstable. Here are his symptoms. Shows no care or emotion for others. Lies uncontrollably. Believes his own lies. Will stop at nothing to have things his way - selfish. In the book he never actually gets diagnosed, it's a post apocalyptic world with no doctors. My question is, how important is it the symptoms match realistically with a diagnosis in real life? Most of the symptoms above point to sociopathic tendencies, but not all of them fit perfectly. Could I just explain them away in a way that shows it's simply his own personality, or should I rewrite it so all symptoms fit the diagnosis, even though it's never diagnosed in the book?