6 Types of Delusions and Possible Causes

6 Types of Delusions and Possible Causes

When do beliefs become delusions?

Delusions are strongly held false beliefs that are resistant to facts or information that contradicts these beliefs. In other words, these beliefs will persist even in the face of overwhelming evidence that disproves them. For example, people with a rare but remarkable delusion called Cotard’s Syndrome believe that they are dead. They can be presented with all the evidence in the world that proves they are alive, but they are unable to change their mind about it.

Within the research community, there are three commonly cited characteristic features of delusions (Feyaerts et al., 2021).

● The content is false or impossible

● It is held with unshakable conviction

● It persists despite rational argument or overwhelming counter-evidence

Causes of Delusions

It is unclear how delusions are caused. They are typically a symptom of various mental health conditions, including schizophrenia, bipolar disorder, Alzheimer’s disease, and Parkinson’s disease. There is no single cause of delusions, as they can arise from a combination of biological, psychological, and environmental factors (Corlett et al., 2010). Here are some of the potential causes of delusions:

Delusion Cause: Biological Factors

Delusions may result from changes in brain chemistry or structure, such as abnormalities in dopamine or glutamate levels, or brain damage due to injury or disease.

Delusion Cause: Genetics

There may be a genetic predisposition to developing delusions, as certain genes have been linked to an increased risk of developing schizophrenia and other psychotic disorders.

Delusion Cause: Psychological Factors

Delusions may be a result of certain psychological conditions, such as low self-esteem, paranoia, or severe anxiety.

Delusion Cause: Substance Abuse

The use of certain drugs, such as hallucinogens, amphetamines, and cannabis may trigger or exacerbate delusions.

Delusion Cause: Environmental Factors

Trauma, stress, and other environmental factors can trigger delusions in vulnerable individuals. 

“All are lunatics, but he who can analyze his delusion is called a philosopher.”
― Ambrose Bierce

Examples of Delusions

Delusions are complicated, multifaceted, and nuanced symptoms that manifest differently across individuals, time, and cultures. The inconsistency, complexity, and subjectivity of delusions make them hard to define. However, researchers and clinicians often group them into several distinct types. There is no consensus on how best to categorize and describe delusions but below are a few common types of delusions (Bell et al., 2006).

Type of Delusion: Persecutory

Persecutory delusions involve the persistent anticipation of possible future danger that cannot be resolved. People who are suffering from persecutory delusions often demonstrate a great deal of anxiety and worry, and they have the tendency to jump to conclusions. Someone with persecutory delusions might feel like they are constantly being surreptitiously monitored by a nefarious agent or that their friends are conspiring against them. This type of delusion is the most commonly observed for many types of psychosis (Freeman, et al., 2002).

Type of Delusion: Alien Control

Delusions of alien control are understood as the misattribution of self-generated actions to an external source, such as aliens. People suffering from this type of delusion experience their thoughts, speech, and actions as being influenced or replaced by those of external agents rather than attributing them to themselves (Blakemore, et al., 2003). For example, someone suffering from the alien control delusion might experience the act of driving their car as a decision they did not make and behavior that is beyond their control.

Type of Delusion: Grandiose

Grandiose delusions, also referred to as delusions of grandeur, involve having an inflated sense of worth, power, or knowledge, or having a special identity (Knowles et al., 2011). This is an example of something an individual with grandiose delusions is reported to have said:

“I would write books on psychiatric theory… on theology. I would write novels. I had the libretto of an opera in mind. Nothing was beyond me… The major work which would be based on this material would be accurate, provocative, and of profound significance.” (Goodwin & Jamison, 2007). 

Type of Delusion: Thought Broadcasting

People suffering from this delusion believe that their thoughts can be accessed by others and are being broadcasted or transmitted to others without their knowledge or consent through means such as telepathy, radio waves, or other electronic signals (Pawar et al., 2002). This delusion can be exceptionally distressing and lead to paranoia and isolation.

Type of Delusion: Religious

Religious delusions are a type of delusion that involve beliefs or experiences related to religious or spiritual themes. These delusions can occur in individuals with various mental health conditions, such as schizophrenia, bipolar disorder, or major depression, among others.

Examples of religious delusions may include (Siddle et al., 2002):

● The belief that they are a religious figure.

● The belief that they have been chosen by God for a special mission or purpose.

● The belief that they have special religious powers or abilities, such as the ability to heal or perform miracles.

● The belief that they are possessed by demons or evil spirits.

● The belief that religious symbols or texts have a special meaning or significance specifically related to themselves. (Siddle et al., 2002).

Type of Delusion: Somatic

Somatic delusions are also called monosymptomatic hypochondriacal psychosis (Joseph & Siddiqui, 2022). People with somatic delusions believe that they have a serious medical condition, despite medical tests and evaluations indicating otherwise. They may also believe that they are experiencing physical symptoms that are not present or exaggerated, such as pain, burning sensations, or unusual smells, and are unarguably convinced of the severity of their symptoms. The most common type of somatic delusions is that they are infested with parasites, body dysmorphic delusion, and body odor or halitosis.

In Sum

Delusions can be a painful and distressing symptom of neuropsychiatric disorders. They are a challenging symptom to treat because they manifest in a variety of ways that are dependent on a combination of several different factors like genetics and culture. Though the beliefs associated with delusions are resistant to change, even in the face of overwhelming evidence, research suggests that they may be treatable with CBT.


● Bell, V., Halligan, P. W., & Ellis, H. D. (2006). Explaining delusions: a cognitive perspective. Trends in cognitive sciences, 10(5), 219-226.

● Corlett, P. R., Taylor, J. R., Wang, X. J., Fletcher, P. C., & Krystal, J. H. (2010). Toward a neurobiology of delusions. Progress in neurobiology, 92(3), 345-369.

● Feyaerts, J., Henriksen, M. G., Vanheule, S., Myin-Germeys, I., & Sass, L. A. (2021). Delusions beyond beliefs: a critical overview of diagnostic, aetiological, and therapeutic schizophrenia research from a clinical-phenomenological perspective. The Lancet Psychiatry, 8(3), 237-249.

● Freeman, D., Garety, P. A., Kuipers, E., Fowler, D., & Bebbington, P. E. (2002). A cognitive model of persecutory delusions. British Journal of Clinical Psychology, 41(4), 331-347.

● Goodwin, F. K., & Jamison, K. R. (2007). Manic-depressive illness: bipolar disorders and recurrent depression (Vol. 2). Oxford university press.

● Knowles, R., McCarthy-Jones, S., & Rowse, G. (2011). Grandiose delusions: A review and theoretical integration of cognitive and affective perspectives. Clinical Psychology Review, 31(4), 684-696.

● Joseph SM, Siddiqui W. Delusional Disorder. [Updated 2022 Jul 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.

● Pawar, A., Mullins, S., & Spence, S. A. (2002, January). Dissecting psychotic phenomenology: Thought broadcasting. In Schizophrenia Research (Vol. 53, No. 3, pp. 64-65)