The exact cause of paranoia is unknown. Potential causal factors may be genetics, neurological abnormalities, changes in brain chemistry, and stress. Paranoia is also a possible side effect of drug use and abuse (for example, alcohol, marijuana, amphetamines, cocaine, PCP). Acute, or short term, paranoia may occur in some individuals overwhelmed by stress.
The Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), the diagnostic standard for mental health professionals in the United States, lists the following symptoms for paranoid personality disorder:
suspicious; unfounded suspicions; believes others are plotting against him/her
preoccupied with unsupported doubts about friends or associates
reluctant to confide in others due to a fear that information may be used against him/her
reads negative meanings into innocuous remarks
perceives attacks on his/her reputation that are not clear to others, and is quick to counterattack
maintains unfounded suspicions regarding the fidelity of a spouse or significant other
Patients with paranoid symptoms should undergo a thorough physical examination and patient history to rule out possible organic causes (such as dementia) or environmental causes (such as extreme stress). If a psychological cause is suspected, a psychologist will conduct an interview with the patient and may administer one of several clinical inventories, or tests, to evaluate mental status.
Paula Anne Ford-Martin, The Gale Group Inc., Gale, Detroit,