Delusions: Definition, Causes, & Examples

• The content is false or impossible
• It is held with unshakable conviction
• It persists despite rational argument or overwhelming counter-evidence​

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.

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: Guilt
People suffering from delusions of guilt believe that they are responsible for a particular event or situation without any evidence to support this belief. They often believe that they have committed a serious offense or sin and that they are deserving of punishment. They may also believe that they are responsible for events or situations that are outside of their control, such as natural disasters or accidents (Kiran & Chaudhury, 2009). For example, someone with this delusion might feel that they were responsible for Hurricane Katrina.

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.

Another important distinction is that illusions are a common occurrence in healthy people and are simply a byproduct of how the brain works. Our brains are essentially prediction machines that have learned over time how the world works and what we can expect as we move through it. These predictions influence our sensory experience in such a way that we are more likely to have the experience we predict than the one that aligns with reality. 

Visual illusions are a common example of how we see what we expect over what is there. One popular visual illusion is the Muller-Lyer illusion. Given how we typically experience the world and what our brains expect we see one of these lines as longer than the others. However, in reality, all the lines are the same length.​​

• “The belief that one’s own view of reality is the only reality is the most dangerous of all delusions.” – Paul Watzlawick
• “No man is happy without a delusion of some kind. Delusions are as necessary to our happiness as realities.” – Christian Nestell Bovee
• “The house of delusions is cheap to build but drafty to live in.” – A. E. Housman
• “Every journey into the past is complicated by delusions, false memories, false namings of real events.” – Adrienne Rich
• “Our mind is like a cloudy sky: in essence clear and pure, but overcast by clouds of delusions. Just as the thickest clouds can disperse, so, too, even the heaviest delusions can be removed from our mind.” – Kelsang Gyatso
• “He had delusions of adequacy.” – Walter Kerr
• “Schizoaffective disorder is a big mental mash-up of a disease. It combines just about every disorder, from depression, delusions, and paranoia to mania, schizophrenia and hallucinations. My mother bounced between all of these regularly while raising me alone in our Hollywood home.” – Shawn Amos​​

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