Delusions, Delusional Disorders, and Paranoia

Delusions (dih-LOO-zhunz) are one or more false beliefs that people hold despite either the lack of evidence the belief is true or clear evidence the belief is not true. Delusional disorders are the classification that psychologists previously labeled as paranoid personality disorder.

John's Story

The next morning, John saw the same group of guys huddled around his locker. This time when he approached, they shouted, “Surprise!” and presented him with a new CD for his birthday. With embarrassment, he realized they had probably been discussing his birthday surprise the day before on the soccer field. He wondered what had caused him to doubt himself and his friends. Was it paranoia or a simple misunderstanding?

What Are Delusions, Delusional Disorders, and Paranoia?

Imagine being completely convinced that someone is following you, to the point where you even call the police several times. Or, imagine believing that your friend is spreading horrible rumors behind your back, although there is no reason to think she is. Or, imagine thinking that you are about to release a new hit record when you are not a recording artist, or that there is something physically wrong with you when your doctor has found nothing to indicate a physical problem.

These thoughts may sound ridiculous, but they help to illustrate what it means to be delusional. It is normal for people to have occasional thoughts that, for example, a boss, teacher, or friend is “out to get them.” Delusions are different, however. A person with delusions holds on to unfounded beliefs for a long time (more than a month) and is certain that they are true despite evidence to the contrary.

Delusions often are classified into the following subtypes:

Delusions often are a symptom of serious psychotic (sy-KOT-ik) disorders, the most common being schizophrenia (skit-suh-FREEnee-uh). Besides delusions, other symptoms of schizophrenia include hallucinations * , disorganized thoughts and speech, and bizarre and inappropriate behavior. The onset of schizophrenia typically occurs during late adolescence or early adulthood.

If a person has delusions, but none of the other symptoms of schizophrenia, doctors may diagnose a delusional disorder, in which the delusions are not as bizarre as they are with schizophrenia. A delusion is bizarre if it is clearly impossible and not derived from ordinary experiences, such as believing a stranger has replaced your internal organs with someone else's organs, without leaving any scar. Delusions that involve situations that could actually occur in real life, such as being followed or being poisoned, or having a serious illness, are not considered bizarre. Unlike schizophrenia, delusional disorder usually begins in middle age (ages 35 to 55 years) or later. Delusional disorder generally does not interfere with everyday functioning and thinking. Many people with delusional disorder can keep their jobs and, on the whole, their personalities do not change. However, when delusions occur, the false beliefs often prove to be a long-term problem. Some people with delusions can become dangerous or violent, threatening harm to themselves or others.

Paranoia is not a particular disorder; rather, it is experiencing reality in an unrealistic manner. For example, John experienced paranoia when he wrongly believed that his friends were out to get him. A person whose phone was once tapped and was thereafter cautious about stating confidential information over the telephone might be considered reasonably concerned rather than paranoid. In contrast, a person who fears deeply that his or her phone is tapped, although it never has been before and there is compelling evidence this is not true, may be considered paranoid. The key issue is not the behavior itself so much as its basis in reality.

Common characteristics of people who tend to be paranoid include the following:

Like many personality traits, paranoia is something that can occur in different degrees of severity. In its milder forms, a person may feel paranoid occasionally or only in certain situations. John, for example, experienced paranoia one day, but he generally does not feel paranoid on a daily basis. In its more severe forms, however, paranoia can seriously limit an individual's ability to function normally. People with significant levels of paranoia may misinterpret reality and experience delusions consistently.

Even people with severe paranoia may function normally much of the time if, for instance, they have a paranoid delusion that affects only one aspect of their life. For example, an individual might become obsessed with the idea that a particular chain of restaurants is conspiring to poison unsuspecting customers. He or she might stop eating in those restaurants and may even go so far as to call the local health department to investigate. Despite this delusion, the individual may still function normally in other respects.

Medical and scientific experts do not fully understand the cause or causes of paranoia. Many healthy people experience paranoid feelings at some point in their lives, just as John did, and certain situations may increase the likelihood that someone experiences paranoid feelings. For example, evidence suggests that immigrants are more prone to suspiciousness and paranoia as a result of the language and other cultural barriers they face. People in the majority culture may misunderstand the immigrants' suspiciousness and react with hostility, which creates even more mistrust and misunderstanding.

Paranoia can accompany a number of illnesses. It is associated with certain neurological conditions such as temporal lobe epilepsy * and some forms of dementia * associated with aging, such as Alzheimer's disease * . People who use drugs such as cocaine * or amphetamines * can repeatedly also experience paranoia. In addition, paranoia is associated with mental disorders such as paranoid schizophrenia (skit-so-FREE-nee-uh) and paranoid personality disorder.

Paranoid Schizophrenia

Schizophrenia is a serious mental disorder that causes people to experience hallucinations, delusions, and other confusing thoughts and behaviors that distort their view of reality. Doctors have come to understand that schizophrenia is likely the result of brain differences or chemical imbalances within the brain. However, schizophrenia is a complex and disabling disorder, and scientists and medical professionals do not fully understand it. Schizophrenia is a disorder that can assume many different forms or subtypes. Paranoid schizophrenia is one of the subtypes. (The others are catatonic, disorganized, undifferentiated, and residual.)

None of the other major characteristics associated with schizophrenia, such as disorganized speech, inappropriate behavior, or inappropriate emotional reactions, is present in people with paranoid schizophrenia, and the age at which this disorder begins tends to be later than it is for the other forms of schizophrenia. People with paranoid schizophrenia are more likely to succeed in holding a job and living independently compared with people with other subtypes of schizophrenia.

Paranoid Personality Disorder

Paranoid personality disorder is one of several different types of personality disorders (others include narcissistic, dependent, avoidant, and antisocial). All personality disorders cause individuals to behave inappropriately in many different situations. These disorders typically lead to problems in social, school, and work settings, and cause the affected person significant internal distress. The personality patterns that develop later into personality disorders usually begin during childhood or adolescence. The persistent nature of these conditions makes them particularly difficult to treat.

The key characteristic of paranoid personality disorder is a pattern of deep distrust of others. Unlike people who have paranoid schizophrenia and whose ideas may be totally bizarre or out of touch with reality, people with a paranoid personality disorder are not completely out of touch with reality, but they are out of step with it. Their belief that other people are untrustworthy colors all aspects of their life and, as a result, they have difficulty forming close relationships. Some common characteristics of people with paranoid personality disorder are as follows:

How Common Are Delusions, Delusional Disorders, and Paranoia?

Paranoid personality disorder is more common in males than in females. Overall, it affects between 0.5 percent and 2.5 percent of the population, according to the National Alliance on Mental Illness. Frequently, an individual who has schizophrenia also has relatives with paranoid personality disorder, and this link suggests the two conditions may have a genetic * component.

How Do People Know They Have Delusions, Delusional Disorders, or Paranoia?

Some possible signs of paranoid personality disorder may appear in childhood or adolescence and include difficulties making friends and relating to others, the tendency to be a loner in social situations, and poor performance in school.

How Do Doctors Treat Delusions, Delusional Disorders, and Paranoia?

Treatment for delusions usually involves regular meetings with a doctor, usually a psychologist or psychotherapist, who specializes in treating mental disorders. People with delusions tend to resist treatment at first and deny there is a problem. Doctors establish a cooperative relationship with these people, listening to their thoughts, easing their fears, and suggesting ways of coping. Some medications, particularly those used to treat depression and psychotic disorders, may help as well. Hospitalization may be necessary if people show signs of dangerous behavior or suicidal tendencies as a reaction to the delusional beliefs.

See also Hallucination • Personality and Personality Disorders • Psychosis • Schizophrenia


Books and Articles

Amador, Xavier. I Am Not Sick, I Don't Need Help! How to Help Someone with Mental Illness Accept Treatment. 10th edition. Peconic, NY: Vida Press, 2011.

Gerrans, Philip. The Measure of Madness: Philosophy of Mind, Cognitive Neuroscience, and Delusional Thought. Boston: Bradford Books/MIT Press, 2014.

Long, Liza. The Price of Silence: A Mom's Perspective on Mental Illness. New York: Plume, 2014.


Out of the Fog. “Paranoid Personality Disorder (PPD).” (accessed December 2, 2015).


Mental Health America. 2000 N Beauregard St., 6th Fl., Alexandria, VA 22311. Toll-free: 800-969-6642. Website: (accessed December 2, 2015).

National Alliance on Mental Illness. 3803 N Fairfax Dr., Suite 100, Arlington, VA 22203. Toll-free: 800-950-6264. Website: (accessed May 26, 2016).

* hallucinations (ha-LOO-sin-AYshuns) are when a person sees or hears things that are not really there. Hallucinations can result from nervous system abnormalities, mental disorders, or the use of certain drugs.

* temporal lobe epilepsy (EPuh- lep-see) is a form of epilepsy that affects the part of the brain located beneath the sides of the head, near the ears. Also called complex partial epilepsy.

* dementia (dih-MEN-shuh) is a loss of mental abilities, including memory, understanding, and judgment.

* Alzheimer's (ALTS-hy-merz) disease is a condition that leads to a gradual worsening loss of mental abilities, including memory, judgment, and abstract thinking, as well as changes in personality.

* cocaine (ko-KAYN) is a stimulant, a drug that produces a temporary feeling of alertness, energy, and euphoria.

* amphetamines (am-FET-ameenz) are stimulants, drugs that produce a temporary feeling of alertness, energy, and euphoria.

* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)