This intra-psychic perspective emphasizes that the cause of paranoid cognitions is inside the head of the people (social perceiver), and dismisses the possibility that paranoid cognition may be related to the social context in which such cognitions are embedded. This point is extremely relevant because when origins of distrust and suspicion (two components of paranoid cognition) are studied many researchers have accentuated the importance of social interaction, particularly when social interaction has gone awry. Even more, a model of trust development pointed out that trust increases or decreases as a function of the cumulative history of interaction between two or more persons.Another relevant difference can be discerned among "pathological and non-pathological forms of trust and distrust". According to Deutsch, the main difference is that non-pathological forms are flexible and responsive to changing circumstances. Pathological forms reflect exaggerated perceptual biases and judgmental predispositions that can arise and perpetuate them, are reflexively caused errors similar to a self-fulfilling prophecy. It has been suggested that a "hierarchy" of paranoia exists, extending from mild social evaluative concerns, through ideas of social reference, to persecutory beliefs concerning mild, moderate, and severe threats. Physical
A paranoid reaction may be caused from a decline in brain circulation as a result of high blood pressure or hardening of the arterial walls.Drug-induced paranoia, associated with cannabis, amphetamines, methamphetamine and similar stimulants has much in common with schizophrenic paranoia; the relationship has been under investigation since 2012. Drug-induced paranoia has a better prognosis than schizophrenic paranoia once the drug has been removed.
For further information, see stimulant psychosis and substance-induced psychosis. Based on data obtained by the Dutch NEMESIS project in 2005, there was an association between impaired hearing and the onset of symptoms of psychosis, which was based on a five-year follow up. Some older studies have actually declared that a state of paranoia can be produced in patients that were under a hypnotic state of deafness. This idea however generated much skepticism during its time. Diagnosis
In the DSM-IV-TR, paranoia is diagnosed in the form of:
Paranoid personality disorder (F60.0)
Paranoid schizophrenia (a subtype of schizophrenia) (F20.0)
The persecutory type of delusional disorder, which is also called "querulous paranoia" when the focus is to remedy some injustice by legal action (F22.8)According to clinical psychologist P. J. McKenna, "As a noun, paranoia denotes a disorder which has been argued in and out of existence, and whose clinical features, course, boundaries, and virtually every other aspect of which is controversial. Employed as an adjective, paranoid has become attached to a diverse set of presentations, from paranoid schizophrenia, through paranoid depression, to paranoid personality—not to mention a motley collection of paranoid psychoses, reactions, and states—and this is to restrict discussion to functional disorders. Even when abbreviated down to the prefix para-, the term crops up causing trouble as the contentious but stubbornly persistent concept of paraphrenia".At least 50% of the diagnosed cases of schizophrenia experience delusions of reference and delusions of persecution.