Around 40 percent of people with schizophrenia will have the paranoid type. This is one of five sub-types of schizophrenia. Paranoid schizophrenia tends to appear later in life, usually around the age of 25 to 30. The main features are a preoccupation with one or more delusions or frequent auditory hallucinations, but nothing prominent in terms of disorganized speech, flat or inappropriate emotions.

The delusional content (the beliefs) of the person with paranoid schizophrenia is marked by grandiosity, or persecution, or both. Onset can be fairly rapid but may be difficult for others to recognize it for what it is. Anger, irritation or argumentative behavior may be the most prominent features, as is extreme jealousy.

Russell Crowe's portrayal of the esteemed mathematician Dr John Forbes Nash in, ‘A Beautiful Mind' (2001) provides a dramatized example. In the movie we initially see the world through the eyes of Nash as he is approached by an agent to help in the decoding of sophisticated secret transmissions. We are drawn into thinking that Nash has a special ability to see secret codes where others cannot. His covert work is apparently fraught with danger as he is chased by foreign agents intent on doing him harm, but he must continue as a matter of national security. As the movie progresses we see Nash's world through the eyes of his wife. We see Nash's secret work room covered in notes from floor to ceiling. We watch as Nash takes his decoding to a secret ‘drop' which is no more than a derelict building. We now understand that the agent with whom he has been working and other significant people in his life are hallucinations. The already insular and increasingly bizarre world that Nash inhabits eventually collapses around him and treatment becomes enforced.

By its own admission the movie is based on a loose interpretation of Nash's life. What it does provide however is a snapshot of how grandiose delusions may be coupled with the perception that the actions of others will bring harm.

A combination of voices and paranoia can be terrifying. Robert Bayley's first hand account provides a prime example:

            "The voices and visions . . persecute me by way of an unwavering commentary and ridicule to deceive, derange and force me into a crippling world of paranoia. Their comments are abrasive and all-encompassing and have resulted in periods of suicidal behavior and self-mutilation".

Delusions and hallucinations represent the ‘positive' symptoms of psychosis, so-called because they are present. By contrast, ‘negative' symptoms refer to the absence of behavior, for example, not showing emotions. Delusions, hallucinations and paranoid thinking are not however confined to people with schizophrenia. They are probably better thought of at extreme end of a continuum of experiences found in the general population.