A chronic personality disorder in which the individual develops systematized, sometimes permanent, and mainly persecutory delusions in a setting of otherwise undisturbed thought. Paranoia must be distinguished from paranoid schizophrenia, in which the same delusions occur but accompanied by hallucinations and disturbances of thought processes and personality.

Paranoid reactions are displayed by most people at one time of another in response to severe disappointment or humiliation. The reaction is the mistaken belief that the sufferer is the center of attention and that he is being talked about, usually in a critical way that invades his privacy and embarrasses him.

Paranoia is a state in which the person experiences constant "paranoid reactions" and where these reactions cannot be dispelled by others. Suspicion and resentment of others arise, and the person takes innocent matters to be a direct attack on him. He usually feels that his true worth is not recognized, and he often has grandiose ideas about what his true worth is.

Temporary paranoid reactions are fairly common and usually harmless---providing they are not associated with other thought disorders or personality changes---although they may be irritating for the family and colleagues of the sufferer. In contrast, true paranoia is relatively rare and can cause considerable annoyance and harm to innocent people outside the sufferer's immediate circle. It is not easy to treat, but is sometimes helped by psychotherapy.