A delusion is a strongly held belief that is not shared by the person's culture, that resists contrary evidence, and that significantly affects how the person sees the world. The National Institute of Mental Health (NIMH) describes delusions as one of the core positive symptoms of schizophrenia, alongside hallucinations and disorganised thinking. They are also among the most misunderstood — both by the public and, sometimes, by clinicians who try to argue patients out of them rather than understand the experience first.
Delusions are organised false beliefs with recognisable patterns; the type a person experiences carries clinical meaning and shapes the kind of help they need.
What makes a belief a delusion?
Three features generally need to be present:
- Conviction — the person holds the belief with high certainty
- Incorrigibility — counter-evidence does not shake the belief in the way it would for an ordinary opinion
- Cultural deviation — the belief is not shared by others in the person's cultural or religious community
This last point matters. A belief in spirits, divine messages, or unseen forces is not a delusion if it fits within the person's faith tradition. Clinicians are trained — though not always perfectly — to consider context before classifying a belief as pathological.
Persecutory delusions
The most common type in schizophrenia. The person believes they are being followed, spied on, plotted against, harassed, or targeted for harm. The perceived perpetrators range from specific individuals (a neighbour, an ex-partner) to organisations (the FBI, a corporation, a church) to broad groups (the government, "they").
Persecutory beliefs often emerge gradually from a generalised sense that something isn't right — sometimes called the "delusional mood" or "atmosphere" — and crystallise around specific people or events that the brain assembles into a coherent threat narrative.
Delusions of reference
The belief that ordinary, unrelated events carry hidden personal meaning. A song on the radio is "speaking to me." A stranger's glance is a coded signal. The pattern of cars on a street is a message. These beliefs are extremely common in early schizophrenia and often appear before more elaborate delusions form.
Delusions of reference are often the symptom that first alerts family members that something has changed. The person may comment that a TV news anchor "kept looking at me" or that song lyrics on the radio "were written for me."
Grandiose delusions
The belief that one has special powers, identity, knowledge, or mission. Examples include believing one has discovered a cure for a major disease, has been chosen by God for a specific purpose, is secretly royalty, or has telepathic abilities. Grandiose delusions appear in schizophrenia but are also a hallmark of bipolar mania with psychotic features.
While they can sound positive, they often lead to risky behaviour — spending sprees, disregard for safety, severe sleep loss — and can be deeply distressing once the episode resolves.
Religious delusions
Beliefs about being chosen by God, possessed by demons, in direct communication with the divine, or having a special religious mission. These overlap with grandiose and persecutory delusions and are particularly important to evaluate in cultural context.
Somatic delusions
Fixed false beliefs about the body. Common variants include:
- Belief that organs are rotting, missing, or have been replaced
- Belief in an undiagnosed serious illness despite medical evidence to the contrary
- Belief that the body emits an offensive smell
- Belief that one is infested with parasites (delusional parasitosis, more common in older adults and stimulant users)
Erotomanic delusions
The belief that another person — often someone of higher status or a celebrity — is in love with the patient. The patient may believe that this love is being communicated through hidden signals or coded behaviour. Erotomanic delusions can fuel persistent unwanted contact and, in rare cases, escalating behaviours that draw legal attention.
Jealous delusions
The fixed false belief that a partner is unfaithful, often based on misinterpreted evidence (a footprint, a stray hair, an ambiguous text). Sometimes called "Othello syndrome." These delusions are clinically important because they carry meaningful risk of intimate partner conflict.
Thought-related delusions
These involve the experience of thinking itself and are particularly characteristic of schizophrenia:
- Thought insertion — feeling that thoughts are being put into one's mind by an outside force
- Thought withdrawal — feeling that thoughts are being removed
- Thought broadcasting — feeling that one's thoughts are audible or transmitted to others
These were originally described by German psychiatrist Kurt Schneider as "first-rank symptoms" and remain clinically suggestive of schizophrenia, though they can also occur in other conditions.
Control delusions
The belief that one's actions, feelings, or impulses are being controlled by an outside agent — a person, organisation, alien force, or technology. The person may describe their body as being "moved" by an external operator.
Bizarre vs non-bizarre
The DSM distinguishes bizarre delusions (clearly impossible, like having one's organs replaced with mechanical parts) from non-bizarre delusions (theoretically possible, like being followed by an ex-partner). Bizarre delusions are more strongly associated with schizophrenia; non-bizarre delusions can occur in delusional disorder, paranoid personality features, or in response to stress.
How delusions are treated
Treatment is rarely about argument. Decades of clinical experience and the NICE guideline for psychosis and schizophrenia in adults (CG178) emphasise that telling someone "that isn't real" almost never helps and usually damages trust. Effective approaches include:
- Antipsychotic medication — reduces conviction and intensity for most people
- Cognitive Behavioural Therapy for psychosis (CBTp) — works with the meaning, distress, and impact of beliefs rather than confronting them head-on
- Family interventions — equip relatives with strategies that reduce conflict
- Time and engagement — many delusions soften gradually as the person feels safer
A delusion is leading to behaviour that endangers the person or others — refusal to eat, stopping essential medication, threatening contact with a perceived persecutor, or any thoughts of self-harm.
For families
If someone you love is in the grip of a delusion, the most useful stance is calm curiosity rather than debate. Ask what the experience is like for them. Acknowledge how distressing it must be. Reserve disagreement for the moments when it's necessary for safety, and do not expect to win arguments. Trust is what keeps the door open for treatment.
This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.