Delusional Disorder Fast Facts

Delusional disorder (DD) is a mental condition in which a person has very strong beliefs in clearly untrue things.

DD most often develops in middle to late adulthood, but it can appear earlier.

People with paranoid personality disorder sometimes develop delusional disorder.

The delusions of DD may be similar to those of schizophrenia, but DD lacks many of schizophrenia’s other symptoms.

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DD most often develops in middle to late adulthood, but it can appear earlier.

What is Delusional Disorder?

Delusional disorder (DD) is an illness characterized by a person’s firm belief in one or more things that are demonstrably untrue. People with DD misinterpret situations and the actions of others to support their beliefs, and they refuse to change their beliefs even when presented with clear evidence to the contrary.

Their delusions may be plausible situations, such as being followed or persecuted, but their beliefs are either wholly untrue or exaggerated. In other cases, the delusions may be centered on situations that are either extremely unlikely or impossible.

People with DD are often able to function well aside from their delusions. This differentiates DD from other psychotic disorders, such as schizophrenia, which usually produce more severe impairments.

Symptoms of Delusional Disorder

Common symptoms of DD, in addition to the delusions themselves, include:

  • Irritability or persistent anger
  • Feelings of being taken advantage of
  • Suspicion of others’ motives
  • Preoccupation with the loyalty of others
  • Misinterpreting the words and actions of others as threatening
  • Reacting quickly and strongly to perceived wrongs
  • Holding grudges
  • Having hallucinations related to the delusions

Some of the symptoms of delusional disorder are similar to those of paranoid personality disorder (PPD), and people with PPD may develop DD.

Types of Delusional Disorder

DD is grouped into subtypes depending on the subject of the delusions. The subtypes include:

  • Grandiose. In this type, the person has an exaggerated sense of their own power, status, or importance.
  • Persecutory. A person with this type believes that others mean to harm, exploit, or manipulate them (or someone close to them).
  • Jealous. In this type, the person believes that their spouse or partner is being unfaithful to them.
  • Erotomanic. A person with this type believes that someone specific, often a celebrity or famous person, is in love with them.
  • Somatic. In this type, the person is fixated on an imagined medical illness or condition.
  • Thought broadcasting. People with this type believe that other people can perceive their thoughts.
  • Thought insertion. People with this type believe that thoughts are being inserted into their minds from outside sources.
  • Mixed. This type combines the delusions of two or more of the other types.

What Causes Delusional Disorder?

The exact cause of DD has not yet been discovered. Several factors, however, seem to put an individual at increased risk of DD.

  • Family history and genetics. People with DD often have a family history of DD itself or schizophrenia. Therefore, scientists suspect a connection between these disorders and a possible genetic component to DD. Still, no definite association with any gene or group of genes has been discovered to date.
  • Brain structure and function. Some studies have found differences in the brains of people with DD compared to healthy brains.
  • Psychological factors. Research has found an association between psychological factors such as stress or social isolation and increased risk of DD.
  • Substance abuse. People who abuse alcohol or drugs are at an increased risk.

Is Delusional Disorder Hereditary?

Scientists have not yet been able to identify a specific genetic component that increases the risk of DD. Inherited genes may increase an individual’s susceptibility to DD, but the disorder’s actual development may result from external triggering circumstances.

How Is Delusional Disorder Detected?

Some symptoms of DD may be apparent before the delusions themselves are brought into the open. Early symptoms can include:

  • Anxiety
  • Irritability
  • Aggression
  • Withdrawal from social situations

How Is Delusional Disorder Diagnosed?

Diagnosis of DD begins with determining that the patient has a cluster of symptoms that meet the diagnostic criteria for the disorder. A doctor will start with a physical exam to rule out biological problems that may be causing symptoms. After these exams, if the doctor suspects that DD or another mental disorder is the cause of the symptoms, they may recommend a psychological or psychiatric assessment to solidify the diagnosis further.

Diagnostic steps may include:

  • A physical exam. This exam will rule out physical conditions that could be causing the symptoms.
  • Psychological assessments. These assessments may take the form of questionnaires or talk sessions with a mental health professional to assess the patient’s mood, mental state, and mental health history. Family members or caregivers may also be asked to participate in these assessments.

The results of the psychological assessments will be compared to the diagnostic criteria for DD in the Diagnostic and Statistical Manual of Mental Disorders (DSM). The DSM criteria for DD include:

  • The patient has one or more delusions that have lasted at least a month.
  • The patient does not have the other psychotic symptoms of schizophrenia. If hallucinations are present, they are related to the delusions.
  • The patient’s behavior is not bizarre, and they are not impaired apart from the delusions.
  • The symptoms aren’t the result of substance use or another medical condition.


How Is Delusional Disorder Treated?

People with DD will not typically seek out treatment because they believe their delusions are real and they don’t need help. However, psychotherapy may help relieve symptoms. In addition, some medicines may be used to treat the disorder’s symptoms and the symptoms of other co-existing mental disorders.


Therapies commonly used to treat DD include:

  • Cognitive-behavioral therapy
  • Family therapy


Medications commonly used to treat DD include:

  • Conventional antipsychotics such as chlorpromazine, fluphenazine, haloperidol, thiothixene, trifluoperazine, perphenazine, or thioridazine
  • Atypical antipsychotics such as risperidone, clozapine, quetiapine, ziprasidone, or olanzapine
  • Antidepressants such as selective serotonin reuptake inhibitors (SSRIs)

How Does Delusional Disorder Progress?

There is no cure for DD, and people with the disorder often experience its symptoms for their entire lives. With treatment, symptoms sometimes resolve, but the delusions can return later.

People with DD can typically function normally in many areas of their lives, but they may become increasingly preoccupied with their delusions as time goes on. Depending on the subject, an intense fixation on the delusions can lead to potentially serious situations.

  • People with the jealous subtype of DD may be moved to act on their suspicions of their partner’s infidelity. This type is more common in men, and it is not uncommon for their delusions to lead to homicide and/or suicide.
  • People with the erotomanic subtype are driven to pursue their misperceived love interest, sometimes to the point of stalking, assault, or other illegal behavior.
  • People with the persecutory subtype may attempt to protect themselves from the people they think are out to get them by resorting to violence or litigation.

How Is Delusional Disorder Prevented?

There is no known way to prevent DD, but early intervention may help someone with the disorder learn to manage their delusions and avoid complications.

Delusional Disorder Caregiver Tips

Many people with delusional disorder also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with DD:

Delusional Disorder Brain Science

Researchers have used functional magnetic resonance imaging (fMRI) to examine the brains of people with DD and compare them to people with schizophrenia. Studies have found many structural similarities in the brains of people with both disorders, and the structural anomalies are distinct from the structures of healthy brains.

The parts of the brain that seem to be affected in DD include the medial frontal/anterior cingulate cortex and the insula. Both of these areas are also affected in schizophrenia, although to a lesser degree. However, areas such as the dorsal and ventral lateral prefrontal cortex, which are involved in schizophrenia, do not seem to be affected in DD.

These findings could help scientists understand which areas of the brain are responsible for delusions in both DD and schizophrenia. Additionally, the structural differences between DD and schizophrenia could point toward the parts of the brain which contribute to schizophrenia’s other symptoms.

Delusional Disorder Research

Title: Adapting and Examining Collaborative Decision Skills Training Among Veterans With Serious Mental Illness (CDST)

Stage: Not Yet Recruiting

Principal Investigator: Emily Treichler, PhD

VA San Diego Healthcare System

San Diego, CA

Recovery-oriented care is imperative for the VA, particularly in mental health programming for Veterans with serious mental illness (SMI). Collaborative decision-making (CDM) is a recovery-oriented approach to treatment decision-making that assigns equal participation and obligation to patients and providers across all aspects of decision-making, thereby empowering patients and facilitating better decision-making based on patient values and preferences. CDM is associated with several important outcomes, including improved treatment engagement, treatment satisfaction, and social functioning. However, current levels of CDM among Veterans with SMI are low, and there is not yet an evidence-based method to improve CDM. Improving Veteran skill sets associated with engaging in CDM is a potential intervention strategy. Collaborative Decision Skills Training (CDST) is a promising new intervention previously developed by the applicant for use in adult civilians with SMI and found to improve relevant skills and improve a sense of personal recovery.

The proposed study has two primary stages. First, a small, one-armed, open-label trial will establish CDST’s feasibility will evaluate CDST among 12 Veterans with SMI receiving services at the VA San Diego Psychosocial Rehabilitation and Recovery Center (PRRC) and identify and complete any needed adaptations to CDST. Stakeholder feedback from Veterans, VA clinicians, and VA administrators will be collected to assess Veteran needs and service context to identify any needed adaptations to the CDST manual or the delivery of CDST to maximize its impact and feasibility. The developers of CDST will review all feedback and make final decisions about adaptations to ensure that CDST retains its essential components to protect against loss of efficacy. For example, a recommendation to adjust role-play topics to reflect the needs of Veterans better would be accepted because it would increase CDST’s relevance without impairing its integrity, but a recommendation to remove all role-plays would not be accepted because it would cause loss of a key component.

Second, CDST will be compared to active control (AC) using a randomized clinical trial of 72 Veterans. The primary outcome measure will be functioning within the rehabilitation context, operationalized as the frequency of Veteran CDM behaviors during Veteran-provider interactions. Secondary outcomes are treatment attendance, engagement, satisfaction, and motivation, along with treatment outcomes (i.e., rehabilitation goal attainment, sense of personal recovery, symptom severity, and social functioning). Three exploratory outcomes will be assessed: Veteran-initiated collaborative behaviors, acute service use, and provider attitudes and behavior. Veterans will be randomly assigned to CDST or AC conditions. Veterans in both groups will attend eight hour-long group sessions held over eight weeks. All Veterans will complete an assessment battery at baseline, post-intervention, and three-month post-intervention follow-up.

Following the trial and adaptation phase, the findings will be used to develop a CDST service delivery manual and design a logical subsequent study. The results of the proposed study will inform the potential for larger trials of CDST and the utility of providing CDST broadly to Veterans with SMI. In addition, the results of this study will expand the current understanding of CDM among Veterans with SMI by providing data that will: 1) identify adaptations needed to optimize CDST for Veterans receiving services in PRRCs; 2) identify possible benefits of CDST; 3) inform the development of alternate interventions or methods to improve CDM; and 4) further elucidate CDM and associated treatment processes among Veterans with SMI receiving VA rehabilitation services.

Title: Feasibility of a Novel Process-based Treatment for Patients With Psychosis (PROBAS)

Stage: Recruiting

Principal Investigator: Susanne Lucae, MD

Max Planck Institute of Psychiatry

Munich, Germany 

Due to the enormous economic and social costs of psychotic-spectrum disorders, increasing the effectiveness of treatment options has become an important subject for psychiatric research. The latest findings in the field of psychotherapy for psychosis show some promising results for so-called Process-based Therapies (PBT), such as the Metacognitive Training (MCT) and Acceptance and Commitment Therapy (ACT) (Barnicot et al., 2020). Instead of trying to change the content of psychotic symptoms such as hallucinations and delusions, PBT directly addresses cognitive processes, which have been found to maintain the disorder’s symptomatology (Hayes et al., 2020). While MCT focuses on changing patients’ cognitive biases by inducing metacognition (Moritz & Woodward, 2007), ACT works with psychological processes such as mindfulness, willingness, and cognitive distancing (Gaudiano & Herbert, 2006). There is a growing study base for PBT in a psychotic outpatient setting. However, research in non-ambulatory settings is rare (Barnicot et al., 2020). Therefore, the current study aims to develop and test the feasibility and safety of a new process-based group therapy program for acutely psychotic patients. The five-week treatment approach will consist of three different modules combining interventions from both MCT and ACT (Module I: Psychoeducation, Module II: Metacognition, Module III: Cognitive Defusion). First preliminary effectiveness and process measures (PANSS, BPRS, WHO-DAS, CGI, BCIS, and CFQ) will also be included to inform the design of future research. Thus, the study will give valuable insights into the feasibility and effectiveness of an innovative psychotherapy approach and breaks new ground in the field of psychotherapy research for psychosis.


Title: The OPUS YOUNG Trial. Early Intervention Versus Treatment as Usual for Adolescents With First-episode Psychosis (OPUS-YOUNG)

Stage: Recruiting

Principal Investigator: Anne K. Pagsberg, PhD

Mental Health Services in the Capital Region

Hellerup, Denmark

The OPUS YOUNG (OY) study investigates the efficacy of early intervention service versus treatment as usual (TAU) for adolescents aged 12-17 years with first-episode psychosis.

In Denmark, the yearly incidence of schizophrenia in youth below 18 years has increased from 137 in 2000 to 477 in 2016. Outcomes in people with schizophrenia spectrum disorders are suboptimal with low quality of life, low recovery rates, substance misuse, higher rates of suicide, violence, and legal problems, low educational and vocational attainment, and a significantly reduced life expectancy of 15-20 years. Schizophrenia implies a significant disease burden that severely impacts patients, their families, the service system, and a significant economic societal burden.

The investigators will include 284 participants aged 12-17 years with an early onset psychosis within the following diagnostic classes: schizophrenia spectrum, psychotic depression, or drug-induced psychosis. The design is an independent, investigator-initiated, pragmatic, randomized clinical trial with blinded outcome assessment. Participants are randomized 1:1 to OY or TAU. Participants in OY are offered two years of specialized intervention (OY) regardless of age, while participants in TAU are switched to adult psychiatry at the age of 18. OY builds on the Danish evidenced-based intervention for young adults, OPUS, adjusted to meet the specific needs of adolescents: intensified support for caretakers and relatives including siblings; social cognition and interaction treatment; and individual cognitive-behavioral case management. In addition, OY addresses the specific challenges of psychopharmacologic treatment in youth; supported transition to adult care after OY; school or educational support; and prevention and treatment of substance misuse. The primary endpoint is improved functioning in daily and social life after 24 months. Secondary outcome measures are psychopathology, quality of life, family stress, retention in treatment and school/employment, and healthcare consumption. The clinical and societal perspective of a large-scale implementation is improved prevention of the negative consequences of early-onset psychosis and a reduced burden of severe mental illness.

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