|Paranoid personality disorder|
|Classification and external resources|
|Cluster A (odd)|
|Cluster B (dramatic)|
|Cluster C (anxious)|
Those with the condition are hypersensitive, are easily slighted, and habitually relate to the world by vigilant scanning of the environment for clues or suggestions to validate their prejudicial ideas or biases. They tend to be guarded and suspicious and have quite constricted emotional lives. Their incapacity for meaningful emotional involvement and the general pattern of isolated withdrawal often lend a quality of schizoid isolation to their life experience. 
See the history of paranoia.
It is a requirement of ICD-10 that a diagnosis of any specific personality disorder also satisfies a set of general personality disorder criteria.
World Health Organization, in the ICD-10, points out for different cultures it may be necessary to develop specific sets of criteria with regard to social norms, rules and obligations.
The following conditions commonly coexist (comorbid) with paranoid personality disorder:
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 schizoid and schizotypal personality disorder.
A genetic contribution to paranoid traits and a possible genetic link between this personality disorder and schizophrenia exist. Psychosocial theories implicate projection of negative internal feelings and parental modeling.
Because of reduced levels of trust, there can be challenges in treating paranoid personality disorder. However, psychotherapy, antidepressants, antipsychotics and anti-anxiety medications can play a role when an individual is receptive to intervention.