Suppose I repeatedly insisted to you that all of the men who walked past me in Waikiki leered at me and wanted to sexually assault me. Then suppose that, when we walk in Waikiki side-by-side, you notice that the men who walk past me simply mind their own business; you catch no leering. If I repeatedly make this distrustful insistence to you about men -- that they're all ogling me -- it might be the case that my claim amounts to a paranoid delusion.
Paranoia is often associated with Paranoid Personality Disorder (naturally) and schizophrenia. However, there are cases where it is also found in Borderline Personality Disorder (BPD). In fact, the presence of paranoia is one of BPD's nine main diagnostic criteria.
