Paranoia is a disturbed thought process characterized by excessive anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs concerning a perceived threat. In the original Greek, παράνοια (paranoia) simply means madness (para = outside; nous = mind) and, historically, this characterization was used to describe any delusional state.
Paranoia is distinct from phobia, which is more descriptive of an irrational and persistent fear, usually unfounded, of certain situations, objects, animals, activities, or social settings. By contrast, a person suffering paranoia or paranoid delusions tends more to blame or fear others for supposedly intentional actions that somehow affect the afflicted individual.