A large long-term Norwegian twin study found paranoid personality disorder to be modestly heritable and to share a portion of its genetic and environmental risk factors with the other cluster A personality disorders, schizoid and schizotypal. Patients with this disorder can also have significant comorbidity with other personality disorders, such as schizotypal, schizoid, narcissistic, avoidant and borderline.Ī genetic contribution to paranoid traits and a possible genetic link between this personality disorder and schizophrenia exist. People with PPD may have a tendency to bear grudges, suspiciousness, tendency to interpret others' actions as hostile, persistent tendency to self-reference, or a tenacious sense of personal right. Their reduced capacity for meaningful emotional involvement and the general pattern of isolated withdrawal often lend a quality of schizoid isolation to their life experience. They tend to be guarded and suspicious and have quite constricted emotional lives. They think they are in danger and look for signs and threats of that danger, potentially not appreciating other interpretations or evidence.

People with this personality disorder may be hypersensitive, easily insulted, and habitually relate to the world by vigilant scanning of the environment for clues or suggestions that may validate their fears or biases.

Paranoid personality disorder ( PPD) is a mental illness characterized by paranoid delusions, and a pervasive, long-standing suspiciousness and generalized mistrust of others.

Paranoid personality disorder treatment