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What is a Delusion?

By Olivia Guy-Evans, published Nov 27, 2021

by Saul Mcleod, PhD

Delusions are characterized as fixed and false beliefs that contradict reality. It is the persistent belief in things which are not true. The delusions are false and there is usually contradicting evidence to prove the delusions aren’t true.

Delusions could be the result of misinterpreting events, or they may involve some level of paranoia. Delusions often are a part of a psychotic disorder and can occur alongside hallucinations, such is the case for schizophrenia.

The difference between delusions and hallucinations is that whilst hallucinations are sensations that are not real, such as hearing voices or seeing things which are not there, delusions are the strong beliefs that cannot be true. Despite being different, they are both part of experiencing a false reality.

Delusions can be either bizarre or non-bizarre. Bizarre delusions are characterized as beliefs about something that can never happen, e.g., the belief that an individual has been abducted and cloned by aliens.

Non-bizarre delusions however are beliefs which could be true, such as the belief that an individual is being stalked, that someone is in love with them, or they are being cheated on by a spouse.

What is Delusional Disorder?

Delusional disorder is a condition which is characterized by non-bizarre delusions that involve the misinterpretation of an experience or a perception. People who are diagnosed with delusional disorder can experience realistic types of delusions such as the belief they are being deceived or conspired against, but these are usually highly exaggerated or untrue.

The onset of delusional disorder is typically in middle to later life but can occur at any time. It is also more common in women than men. Often with delusional disorder, the individual will socialize, and function normally and generally do not behave in an obviously unusual manner, which can make this condition difficult to recognize from an outsider’s perspective.

Delusional disorder therefore differs from other psychotic disorders where delusions are present, such as in schizophrenia, as there are other symptoms of those conditions which can affect the functioning of those individuals. off with a small dosage, before potentially increasing this.

Types of Delusions

There are many different types of delusions that can be experienced which can be characterized under delusional disorder. The type of delusional disorder is based on the main theme of the delusions being experienced. The types are as follows:


This type of delusion is the belief that someone, usually someone who is famous or of a higher social status, is in love with the individual. For instance, the person experiencing this delusion may believe that the famous person is communicating secret messages to them on the TV show they star in.

Stalking behavior is often common with this type of delusion as the individual may attempt to make contact with the person they believe loves them.


This type of delusion is the belief that the individual has an over-inflated sense of worth, knowledge, wealth, talent, power, or fame, despite a lack of evidence of this.

For instance, someone with grandiose delusions may believe they have made an important discovery, or they were sent by a religious entity to save the world.


This type of delusion is the belief that the individual, or someone close to them, is being spied on, followed, drugged, cheated on, or mistreated.

They may believe that someone is planning to harm them or someone close to them and thus may make repeated complaints to legal authorities.


This type of delusion is the belief that a romantic partner or spouse is being unfaithful, despite a lack of evidence to prove this.

The individual may believe their partner is meeting their secret lover whenever not in their presence or is sending their lover secret messages.


This type of delusion if the belief that the individual is experiencing physical sensations, bodily dysfunctions, or suffering from a medical condition.

For instance, they may be convinced that they have a rare illness or parasites living underneath their skin, despite no evidence of this being the case.


When the delusions being experienced do not fall into a single category or there are two or more types of delusions being experienced, this would be labelled as having mixed or unspecified types of delusions.


If someone is experiencing symptoms of delusions, they can be tested to see if they have a delusional disorder. Firstly, a doctor would likely investigate the medical history of the individual and perform a medical examination.

Some imaging tests such as magnetic resonance imaging (MRI) may be used in order to rule out any other conditions which may explain the symptoms, such as Alzheimer’s disease or epilepsy.

If delusional disorder is still suspected, the individual may be referred to a trained psychiatrist, psychologist or health professional who will use interview methods and assessment tools to make a diagnosis.

The professional will refer to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) to assess the symptoms against the diagnostic criteria. According to the DSM-IV, for a diagnosis of delusional disorder to be made, the individual would need to have the presence of non-bizarre hallucinations that have lasted for the duration of at least a month.

The individual must never have met the criteria for schizophrenia, meaning that the delusions are not accompanied by most types of hallucinations.

The overall functioning of the individual should also not be affected, except for the immediate consequences of acting on a delusional thought (e.g. if experiencing the jealous type of delusion and choosing to confront a suspected secret lover of a spouse).

The delusions must also not be as a result of a general medical condition or as a result of taking drugs or medication.

Further, the delusions must be separate from any other mental health condition, meaning other conditions need to be ruled out.

Finally, any disturbances in mood, if experienced at all, must be brief when compared with the delusions.

Causes and Risk Factors

Although there is currently not a concrete explanation for what causes delusions, researchers have some ideas as to potential causes or risk factors which may contribute to the onset of delusions.

Genetics may play a part in someone developing delusions since it is more common that those who have family members with a psychotic disorder with delusions, are likely to develop delusions themselves.

For instance, a parent who has delusional disorder or schizophrenia is more likely to have a child who also develops one of these conditions. Delusional disorder specifically tends to be more common among those who are more isolated, such as those with impairments with their vision or hearing.

If someone has problems with vision or hearing, they may be more likely to rely upon inaccurate perceptions of reality if they are less able to see things for how they are, although this is not the case for the majority of those with these impairments.

There could also be some biological causes that produce the onset of delusions. Joyce (2018) investigated the pathobiology of delusions using case studies of patients who had experienced strokes.

It was found that some of those who had focal strokes to the right lateral prefrontal cortex developed delusions. This part of the brain is known to have connections to the basal ganglia and the limbic system, as well as receiving input from the midbrain dopamine neurons.

Dopamine is a neurotransmitter which plays a role in motivation, pleasure, and reward. Dysregulated dopamine has been found to have associations with schizophrenia and those at risk of psychosis, thus suggesting that faulty dopamine signaling could be a precursor of delusion formation.

A further study by Devinsky (2009) found significant associations between the bilateral frontal lobe in the right cerebral hemisphere with delusions.

Damage to this area, a brain region which controls perceptions and thinking, can result in left hemispheric overactivity. The researchers suggested this can result in the left language centers to ‘create a story’ which cannot be compared to reality, corrected, and self-monitored due to damage on the right side.

This can therefore be confused for reality and delusional resistance can occur. Environmental triggers such as high amounts of stress could also be a potential risk factor for the onset of delusions.

A study by Nygaard, Sonne, and Carlsson (2017) found that a significant number of those who developed posttraumatic stress disorder (PTSD) also developed delusions, specifically of the persecutory type. Although not the case for most people who have PTSD, this implies there could be a causal link between trauma and stress with the onset of delusions.

As well as delusional disorder, delusions could be a symptom which is triggered by another mental health condition, such as:

  • Dementia
  • Mood disorders
  • Parkinson’s Disease
  • Schizophrenia
  • Postpartum psychosis
  • Substance-induced psychotic disorder


It may be challenging to initially treat someone who is experiencing delusions since the individual may not recognize that what they are experiencing is not real and this may present some resistance to treatment.

Similarly, since with delusional disorder, there may not be much disruption to everyday life and functioning is normal, individuals may not believe they will require any treatment.

Often it may be that a nonconfrontational and sensitive approach by family or close friends may be recommended to encourage the person experiencing delusions to seek treatment.

The primary treatments for those experiencing delusions are medication and psychotherapy. The main type of medication recommended is antipsychotics. These have shown effectiveness in that many people with delusions who take antipsychotics showed partial improvement to their symptoms.

Typical antipsychotics are medications that are used to block the dopamine receptors in the brain, which is a neurotransmitter believed to be involved in the development of delusions.

These have been used to treat mental health conditions since the 1950s and some of these include:

  • Chlorpromazine (Thorazine)
  • Fluphenazine (Prolixin)
  • Laxapine (Oxilapine)
  • Thiothixene (Navane)
  • Perphenazine (Trilafon)
  • Haloperidol (Haldol)
  • Trifluoperazine (Stelazine)

Atypical antipsychotics are a newer type of medication which are also used to treat delusional disorder but with fewer side effects than the typical antipsychotics.

These work by blocking dopamine and serotonin receptors in the brain and appear to be more effective in treating the symptoms of delusional disorder. Some of these medications include

  • Clozapine (Clozaril)
  • Aripiprazole (Abilify)
  • Asenapine (Saphris)
  • Iloperidone (Fanapt)
  • Risperidone (Risperdal)
  • Olanzapine (Zyprexa)
  • Cariprazine (Vraylar)
  • Ziprasidone (Geodon)

Some other medications which may be used to treat delusional disorder are antidepressants and tranquillisers.

Antidepressants such as selective serotonin reuptake inhibitors (SSRIs) can be used to treat the depressed or anxious feelings which may be experienced alongside the delusions.

Tranquillizers may be used with individuals who are experiencing very high levels of anxiety or are having trouble sleeping due to the delusions being experienced.

Finally, psychotherapy can also be helpful alongside medications as a way to help individuals manage and cope with the stress that goes alongside their delusions.

Cognitive behavioural therapy (CBT) is a common psychotherapy which aims to help a person recognize their thought patterns and behaviours so they can change to more realistic types of thinking.

This can be helpful for individuals with delusional disorder to recognize their unhelpful thoughts they are experiencing and view their delusions from another perspective. Likewise, family therapy can be a part of treatment as well.

The aim of involving family is so that they can learn how to support someone who is experiencing delusions, of which may make an impact on the severity of the delusions being experienced.

Do you or a loved one need mental health help?


Contact the National Suicide Prevention Lifeline for support and assistance from a trained counselor. If you or a loved one are in immediate danger:



Contact the Samaritans for support and assistance from a trained counselor:; email [email protected].

Availiale 24 hours day, 365 days a year (this number is FREE to call):


Rethink Mental Illness:

0300 5000 927

Fact Checking
Simply Psychology content is rigorously reviewed by a team of qualified and experienced fact checkers. Fact checkers review articles for factual accuracy, relevance, and timeliness. We rely on the most current and reputable sources, which are cited in the text and listed at the bottom of each article. Content is fact checked after it has been edited and before publication.

About the Author

Olivia Guy-Evans obtained her undergraduate degree in Educational Psychology at Edge Hill University in 2015. She then received her master’s degree in Psychology of Education from the University of Bristol in 2019. Olivia has been working as a support worker for adults with learning disabilities in Bristol for the last four years.

How to reference this article:

Guy-Evans, O. (2021, Nov 27). What Is a Delusion? Simply Psychology.

APA Style References

Casarella, J. (2020, December 13). Delusions and Delusional Disorder. WebMD.

Devinsky, O. (2009). Delusional misidentifications and duplications: right brain lesions, left brain delusions. Neurology, 72(1), 80-87.

Drake, M. E. (n.d.). Delusional Disorder DSM-5 297.1 (F22). Theravive. Retrieved 2021, August 18, from:

Joyce, E. M. (2018). Organic psychosis: the pathobiology and treatment of delusions. CNS neuroscience & therapeutics, 24(7), 598-603.

Morin, A. (2021, February 13). What Is a Delusion? Very Well Mind.

Nygaard, M., Sonne, C., & Carlsson, J. (2017). Secondary psychotic features in refugees diagnosed with post-traumatic stress disorder: a retrospective cohort study. BMC psychiatry, 17(1), 1-11.

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