What Is Delusional Disorder?

Delusional disorder is a psychotic disorder that can make it hard for a person to distinguish between what’s real and what’s imagined to be true. The primary symptom of this condition is the presence of delusions, which are irrational, unshakeable beliefs that are untrue.

People with delusional disorder may experience bizarre or non-bizarre delusions:

• Bizarre delusions: These are delusions that are physically impossible in our reality. For instance, the person may believe that an organ has been removed from their body without there being any evidence of the procedure.
• Non-bizarre delusions: These are delusions that could possibly occur in real life, although they are often highly exaggerated misinterpretations of situations. For instance, the person may believe that their neighbor is plotting to kill them or that someone walking behind them on the pavement is actually following them.

This article explores the types, symptoms, causes, diagnosis, and treatment of delusional disorder.

Types of Delusional Disorder

Delusional disorder is classified into different types, depending on the type of delusions the person experiences:

• Persecutory type: Persecutory delusions, also known as paranoid delusions, can cause the person to believe that someone is trying to follow, spy on, mistreat, or harm them in some way. As a result, they may make repeated complaints to the authorities for help. 
• Grandiose type: The person has a conviction of some great but unrecognized talents, knowledge, status, or identity. For instance, they may believe they are exceptionally talented or that they have made an important discovery.
• Jealous type: The person may believe that their partner or spouse is cheating on them, even though there is no evidence to support this belief.
• Erotomanic type: The person may believe that someone—often someone famous or important—is in love with them. They may try to contact the person or stalk them, and get into trouble with the authorities as a result.
• Somatic type: Somatic delusions are related to the person’s body, health, or appearance. The person may have a conviction that they have a health condition, a strange appearance, a parasite in their body, or a foul odor emanating from them.
• Mixed type: The person has more than one delusional theme.
• Unspecified type: Where the person's dominant delusional belief is not clearly described in the other specific types.

Symptoms of Delusional Disorder

These are some of the symptoms that may be present with different types of delusional disorder:

• Lack of awareness that the delusions are imaginary
• Inability to accept that the delusions are untrue
• Defensiveness in response to confrontation of the delusion
• Preoccupation with hidden motives of friends and family members
• Fear of being tricked, mistreated, or taken advantage of
• Intense, irrational suspicion and mistrust
• Bizarre or aggressive behavior in response to delusions

Causes of Delusional Disorder

While the exact causes of delusional disorder are unknown, these are some of the risk factors that can contribute to the development of the condition:

• Genetic factors: Delusional disorder has a genetic component and people may be more likely to have this condition if a biological relative has delusional disorder or schizophrenia.
• Biological factors: Abnormalities in certain parts of the brain and imbalances in brain chemicals known as neurotransmitters have been linked to delusional symptoms.
• Environmental factors: Factors such as stress, social isolation, alcohol use disorder, and substance use disorder can make a person more likely to experience delusions.
• Psychological factors: Personality traits such as hypersensitivity, suspicion, distrust, envy, and low-self esteem can cause a person to seek explanations for these feelings, contributing to the formation of delusions.

Diagnosing Delusional Disorder

Healthcare providers diagnose delusional disorder by determining whether the person’s symptoms meet the diagnostic criteria listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), a guiding manual published by the American Psychiatric Association.

The diagnostic process may involve a complete medical history, a physical examination, a comprehensive psychiatric interview, and perhaps other screening tests or questionnaires, in addition to other tests or scans to help rule out other health conditions.

It’s important to note that delusions can occur as a symptom in several mental health and neurological conditions, such as schizophrenia, bipolar disorder, fronto-temporal dementia, Alzheimer’s disease, and Parkinson’s disease, among others.

However, these conditions tend to be accompanied by several other symptoms in addition to delusions, such as hallucinations, disorganized thinking, and abnormal motor behavior, for instance.

Therefore, the diagnostic criteria distinguishes between delusional disorder and other conditions by noting the lack of other psychotic, affective, behavioral, or neurological symptoms.

Treating Delusional Disorder

People with delusional disorder may be unlikely to seek treatment because they may not realize that their delusional beliefs are not true.

This condition can be difficult to treat, because the person’s suspicious nature and delusional beliefs can cause them to believe their loved ones and healthcare providers are trying to harm them. However, recovery is possible, especially if the healthcare provider is able to earn the person’s trust.

Treatment for delusional disorder typically involves:

• Antipsychotic medication: Antipsychotic medications work by improving the balance of neurotransmitters in the brain, thereby reducing delusions. They may also help reduce agitation.
• Cognitive behavioral therapy (CBT): CBT and other types of psychotherapy can help people better recognize and challenge the underlying distorted thinking contributing to the delusions, and help make them less distressing and impairing in everyday life.

A Word From Verywell

If you or a loved one are experiencing delusions, it can be helpful to visit a mental healthcare provider such as a psychologist or psychiatrist as soon as possible. Your primary care doctor can provide a reference, if you need one.