Researchers do not understand fully what chemical or physical changes in the
brain cause paranoia. Paranoia is a prominent symptom that occurs in a variety of different mental disorders, as well as a symptom of certain physical diseases. Furthermore, use of certain drugs or chemicals may cause symptoms of paranoia in an otherwise normal individual.
Paranoia is often manifested as part of the symptom complex of
schizophrenia. In fact, one of the subtypes of schizophrenia is termed "paranoid schizophrenia," which actually refers to a type of schizophrenia in which the individual is particularly preoccupied with
delusions in which the world seems to be pitted against him or her. As with other forms of schizophrenia, sufferers often lack contact with reality, and display
hallucinations, flat or emotionless
affect, and disorganized thinking and behavior.
Paranoid personality disorder is diagnosed when an individual does not have other symptoms of schizophrenia, but a personality that is driven by chronic manifestations of paranoia. These individuals are mistrustful, suspicious, and convinced that the world is out to get them.
In order for an individual to be diagnosed with paranoid personality disorder, he or she must display at least four of the following traits:
- chronically suspicious that people are lying or cheating him or her in some way
- frequently preoccupied with whether people are loyal or trustworthy
- cannot confide in others for fear of being betrayed
- misinterprets benign comments or events as being personally threatening
- harbors long-term grudges against others who are perceived as having been threatening or insulting in some way
- sees others' actions and/or words attacking him or her in some way, and therefore goes on the counterattack
- repeatedly assumes that partner or spouse is unfaithful
Paranoia can also occur as a symptom of other neurological diseases. Individuals suffering from the aftereffects of strokes, brain injuries, various types of
dementia(including
Alzheimer's disease), Huntington's disease, and Parkinson's disease may manifest paranoia as part of their symptom complex. The paranoia may decrease in intensity when the underlying disease is effectively treated, although since many of these diseases are progressive, the paranoia may worsen over time along with the progression of the disease's other symptoms.
A number of different medications and drugs can cause paranoia. These include corticosteroid medications, H-2 blockers (cimetidine, ranitidine, famotidine), some muscle relaxants (Baclofen), antiviral/anti-Parkinson drugs (
amantadine), some
amphetamines(including methylphenidate, or Ritalin), anti-HIV medications, anti-depressants (Nardil). Abused drugs that can prompt paranoia include alcohol, cocaine, marijuana, ecstasy (MDMA), amphetamines (including Ritalin), LSD, and PCP (angel dust). Withdrawal from addictive drugs may also cause symptoms of paranoia.
