Also called folie à deux, this occurs when one person in a relationship that has a delusion influences the other to develop that delusion. This can happen to groups too, referred to as folie à plusiers, and can be seen in cults. 

University of Rochester

Syracuse University

Psychotic disorders are severe mental illnesses characterized by thoughts, perceptions, and behaviors that are so impaired the individual cannot function normally and becomes disconnected from reality. This state of being disconnected from the world is known as psychosis. People with these disorders often lose contact with reality and may experience extreme symptoms like hallucinations and delusions. Schizophrenia is a primary example of a psychotic disorder.

Psychotic Disorders

Previously referred to as paranoid disorder, delusional disorder is characterized by an inability to recognize reality from false beliefs called delusions. It occurs more often in middle age or later in life. This disorder is diagnosed when someone holds one or more non-bizarre delusions as truth for a month or more. These delusions cannot be sourced from culture or other causes. Symptoms include irritability and hallucinations.  

Delusional Disorder

Casarella, J. (2020, July 17). What Is a Psychotic Disorder? WebMD. https://www.webmd.com/schizophrenia/guide/mental-health-psychotic-disorders. 

Psychotic Disorders WebMD

Casarella, J. (2021, April 22). What Is a Shared Psychotic Disorder? WebMD. https://www.webmd.com/schizophrenia/guide/shared-psychotic-disorder. 

What is shared psychotic disorder?

- Hallucinations
- Delusions
- Disorganized speech

Common Symptoms Across Psychotic Disorders

Empirically supported treatments for psychotic disorders. 

Psychotic Disorder Treatments

A sudden and temporary display of psychotic behavior, and can be triggered by extreme stress and trauma. This episode lasts less than a month, and is followed by complete remission, though future relapses are possible. 

Brief psychotic disorder

Schizophrenia is a severe psychological disorder that leads to a profound breakdown in an individual's ability to function, often necessitating hospitalization. It is characterized by significant disruptions in thought, perception, emotion, and behavior, including symptoms like hallucinations, delusions, incoherent thinking, bizarre actions, flat emotions, and a lack of motivation for basic activities. It is important to distinguish schizophrenia from dissociative identity disorder ('split personality'), as the term 'schizophrenia' refers to a 'splitting of psychic functions,' not a divided personality.

Schizophrenia

Shared psychotic disorder

Psychotic Disorder References

Lynn, S. J., Polizzi, C., Merckelbach, H., Chiu, C.-D., Maxwell, R., van Heugten, D., &amp; Lilienfeld, S. O. (2022). Dissociation and dissociative disorders reconsidered: Beyond sociocognitive and trauma models toward a transtheoretical framework. Annual Review of Clinical Psychology, 18(1), 259–289. https://doi.org/10.1146/annurev-clinpsy-081219-102424 

Dissociation and Dissociative Disorders Reconsidered: Beyond Sociocognitive and Trauma Models Toward a Transtheoretical Framework

- Brief Psychiatric Rating Scale (BPRS)
- Abnormal Involuntary Movement Scale (AIMS)
- Extrapyramidal Symptom Rating Scale (ESRS)
- Dyskinesia Identification System Condensed User Scale (DISCUS)
- Clinician-Related Dimensions of Psychosis Symptom Severity (CRDPSS)

Current Scale to measure Psychotic Disorder Symptoms

Psychosis is a condition in which an individual becomes disconnected from the world that most people inhabit. It is the defining feature of a psychotic disorder, where a person's thoughts and perceptions are fundamentally impaired, leading to a loss of contact with reality.

Psychosis

A patient reports a firm belief that their neighbor is secretly a government agent who is replacing their thoughts with new ones via a hidden device. The patient cannot be persuaded otherwise, even when presented with contradictory evidence. This profound disconnection from a commonly shared sense of reality is the central feature of which category of mental illness?

There are different types of Delusional Disorder, depending on  the specific delusion the individual is experiencing:

- Delusional jealousy
- Bizarre
- Erotomania
- Grandiose
- Persecutory
- Somatic
- Mixed
- Thought broadcasting
- Thought insertion
- Unspecified


Types of Delusional Disorder

Certain populations are more vulnerable to this psychotic disorder:
- People who are deaf or hard of hearing
- People who are visually impaired
- People who face language barriers 
- Elderly People

Population at Risk for Delusion Disorder

A study found an association between the HLA-A*03 gene, delusional disorder, and paranoid schizophrenia. It is found that this gene alone, in combination with other HLA genes or other closely linked non-HLA genes, may lead to vulnerability to delusional disorder and paranoid schizophrenia.   

Genetic Association between Delusional Disorder and Paranoid Schizophrenia

Psychotherapy is typically used to treat delusional disorder. The treatment focuses on exploring possible biological and psychological problems and decreasing symptoms by helping the individual work toward reality. A therapist first establishes a trustful bond with the individual by expressing sympathy and accepting their delusions, a supportive response the individual is often not accustomed to from others. Subsequently, the therapist helps increase the individual’s self-confidence, challenges the delusional thought process, and addresses any underlying psychological problems. Cognitive-behavioral therapy and other solution-oriented therapies are particularly useful during this stage of treatment.

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