Paranoia

Paranoia is a thought process thought to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs concerning a perceived threat towards oneself. Historically, this characterization was used to describe any delusional state.

History
The word paranoia comes from the Greek "παράνοια" (paranoia), "madness" and that from "παρά" (para), "beside, by" + "νόος" (noos), "mind". The term was used to describe a mental illness in which a delusional belief is the sole or most prominent feature. In original attempt at classifying different forms of mental illness, Kraepelin used the term pure paranoia to describe a condition where a delusion was present, but without any apparent deterioration in intellectual abilities and without any of the other features of dementia praecox, the condition later renamed "schizophrenia". Notably, in his definition, the belief does not have to be persecutory to be classified as paranoid, so any number of delusional beliefs can be classified as paranoia. For example, a person who has the sole delusional belief that he is an important religious figure would be classified by Kraepelin as having 'pure paranoia'. According to Phelan, M. Padraig, W. Stern, J (2000) paranoia and paraphrenia are debated entities that were detached from dementia praecox by Kraepelin, who explained paranoia as a continuous systematized delusion arising much later in life with no presence of either hallucinations or a deteriorating course, paraphrenia as an identical syndrome to paranoia but with hallucinations. Even at the present time, a delusion need not be suspicious or fearful to be classified as paranoid. A person might be diagnosed as a paranoid schizophrenic without delusions of persecution, simply because their delusions refer mainly to themselves, such as believing that they are a CIA agent or a famous member of royalty.

Use in modern psychiatry
In the DSM-IV-TR, paranoia is diagnosed in the form of:
 * paranoid personality disorder
 * paranoid schizophrenia (a subtype of schizophrenia)
 * the persecutory type of delusional disorder, which is also called "querulous paranoia" when the focus is to remedy some injustice by legal action.

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&mdash;not to mention a motley collection of paranoid 'psychoses', 'reactions', and 'states'&mdash;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."