Delusional Disorder (ICD-11: 6A24) - Complete Coding and Diagnostic Guide
1. Introduction
Delusional disorder represents a singular psychiatric condition characterized by the presence of fixed and unshakeable beliefs that persist despite contrary evidence, maintaining themselves over prolonged periods without the presence of other prominent psychotic symptoms. This condition is distinguished by its peculiar nature: patients maintain relatively preserved functioning in areas unrelated to the delusion, unlike other more severe psychotic disorders.
The clinical importance of delusional disorder resides in its challenging diagnosis and the significant impact it can cause on the lives of patients and their families. Although considered relatively rare when compared to other psychiatric conditions, its lifetime prevalence is around 0.2% of the general population, affecting men and women in a relatively balanced manner. The condition typically manifests in middle adulthood, although it can emerge at any phase of life.
The impact on public health is considerable, especially because delusional disorder frequently goes unnoticed or is diagnosed late. Patients rarely seek treatment spontaneously, as they do not recognize their beliefs as pathological. This results in significant social, occupational, and family consequences, in addition to potential involvement with legal systems in specific cases.
Correct coding of delusional disorder is critical for multiple reasons: it enables appropriate epidemiological tracking, facilitates clinical research, ensures appropriate access to treatment resources, and assures precise medical-legal documentation. The transition to ICD-11 brought important refinements in the classification of this condition, making it essential that healthcare professionals understand the specific criteria and diagnostic nuances.
2. Correct ICD-11 Code
Code: 6A24
Description: Delusional disorder
Parent category: Schizophrenia or other primary psychotic disorders
Official definition: Delusional disorder is characterized by the development of a delusion or set of related delusions, which typically persists for at least 3 months and often for much longer, in the absence of a depressive, manic, or mixed mood episode. The content of the delusions varies between individuals, but is typically stable for each individual, although the delusions may evolve over time.
The definition clearly establishes that other characteristic symptoms of schizophrenia should not be present. This includes clear and persistent hallucinations, prominent negative symptoms, disorganized thinking or experiences of influence, passivity, or control. However, various forms of perceptual disturbances related to the theme of the delusion are still compatible with the diagnosis, including occasional hallucinations, illusions, or misidentification of people.
A fundamental aspect is that, except for actions and attitudes directly related to the delusion or delusional system, affect, speech, and behavior typically remain preserved. This characteristic significantly differentiates delusional disorder from other more deteriorating psychotic conditions.
The definition also establishes important exclusions: symptoms cannot be a manifestation of another medical condition (such as brain tumor) and should not be attributable to the effect of substances or medications on the central nervous system (including corticosteroids) or withdrawal effects.
3. When to Use This Code
Code 6A24 should be applied in specific clinical scenarios where diagnostic criteria are clearly met:
Scenario 1: Isolated Persecutory Delusion A 45-year-old patient presents with an unshakeable conviction that specific neighbors are conspiring to harm him through constant surveillance and sabotage of his belongings. He meticulously documents "evidence" of these actions, has altered routines to "avoid attacks," and has repeatedly sought legal assistance. Despite this, he maintains stable employment, preserved family relationships (except when discussing his beliefs), does not present persistent auditory hallucinations, disorganized thinking, or negative symptoms. The condition has persisted for 8 months without significant mood episodes.
Scenario 2: Erotomania Delusion A 38-year-old woman developed the belief that a senior colleague at work is secretly in love with her, interpreting neutral professional gestures as coded declarations of love. She sends frequent messages, attempts to arrange meetings, and refuses to accept explicit denials as genuine. Outside of this specific theme, she functions adequately in all areas of life, does not present other psychotic symptoms, and the condition has remained stable for 5 months.
Scenario 3: Somatic Delusion A 52-year-old man is convinced that he has a specific parasitic infestation on his skin, despite multiple negative dermatological evaluations. He describes specific cutaneous sensations, brings "samples" for analysis (which consist of normal skin debris), and has consulted various specialists insisting on antiparasitic treatments. He maintains excessive hygiene related to the belief but preserves cognitive, social, and occupational functioning in other areas. The condition has persisted for 7 months.
Scenario 4: Jealous Delusion A 41-year-old patient developed an inflexible conviction of marital infidelity, interpreting neutral evidence (work delays, phone conversations, specific clothing) as proof of betrayal. She constantly checks her spouse's belongings, hires investigators, and repeatedly confronts her partner. She does not present significant depressive symptoms, hallucinations, or other psychotic symptoms. She functions adequately at work and in other social relationships. The condition has persisted for 6 months.
Scenario 5: Delusion of Reference A 50-year-old patient believes that television programs, news, and public conversations contain messages specifically directed at him, often with derogatory or threatening content. He records these "messages," has altered media consumption habits, and developed specific avoidance behaviors. He does not present disorganized thinking, clear auditory hallucinations, or negative symptoms, maintaining employment and self-care. The condition has persisted for 4 months.
Scenario 6: Mixed Delusion with Preserved Functioning A 55-year-old woman presents with a delusional system involving the belief that she is being monitored by specific organizations due to special knowledge she possesses, combined with interpretations that environmental signals provide instructions on how to proceed. Despite these complex beliefs, she maintains adequate social and occupational functioning, does not present typical schizophrenic symptoms, and the condition has remained stable for 10 months.
4. When NOT to Use This Code
Code 6A24 should not be applied in various situations where other conditions better explain the clinical presentation:
Presence of Prominent Schizophrenic Symptoms: When the patient presents with clear and persistent auditory hallucinations (especially voices commenting on behaviors or conversing with each other), significant negative symptoms (affective blunting, alogia, avolition), evident disorganized thinking, or experiences of control and passivity, the appropriate diagnosis is schizophrenia (6A20), not delusional disorder.
Concomitant Mood Episodes: If delusions occur exclusively during major depressive or manic episodes, or if there is simultaneous presence of psychotic and mood symptoms of equivalent magnitude, the correct diagnosis is schizoaffective disorder (6A21) or mood disorder with psychotic features.
Generalized Functional Deterioration: When there is significant impairment in multiple areas of life not directly related to delusional content, including self-care, broad social functioning, and occupational capacity, other psychotic conditions should be considered.
Delusions Secondary to Medical Conditions: When delusions are clearly attributable to neurological conditions (brain tumors, dementias, delirium, temporal lobe epilepsy), endocrine conditions (hyperthyroidism, Cushing's disease), or other general medical conditions, the appropriate code is that of the underlying medical condition.
Substance-Induced Delusions: If delusions clearly arise in the context of intoxication, chronic use, or withdrawal from substances (alcohol, stimulants, corticosteroids, antiparkinsonian agents), the appropriate code belongs to the category of substance-related disorders.
Insufficient Duration: When delusions persist for less than 3 months, the diagnosis of delusional disorder should not be established, and it may be more appropriate to consider brief psychotic disorder or await clinical evolution.
Culturally Sanctioned Beliefs: Beliefs shared by specific cultural, religious, or subcultural groups do not constitute pathological delusions, even when they seem implausible to observers external to the group.
5. Step-by-Step Coding Process
Step 1: Assess Diagnostic Criteria
Diagnostic confirmation requires comprehensive psychiatric evaluation including detailed clinical history, mental status examination, and frequently collateral information from family members or other informants. The clinician must establish:
Presence of Delusion: Identify fixed, unshakeable, and false belief maintained with absolute conviction despite contrary evidence. The delusion must be clearly implausible and not merely an extreme interpretation of real experiences.
Adequate Duration: Confirm that delusions persist for at least 3 months. Document onset, evolution, and stability of delusional content.
Absence of Schizophrenic Symptoms: Systematically assess absence of persistent and clear auditory hallucinations, prominent negative symptoms, disorganized thinking, and experiences of passivity or control.
Preserved Functioning: Verify that, except in areas directly related to the delusion, the patient maintains adequate functioning, including self-care, basic cognitive abilities, and social skills.
Useful instruments include structured interviews such as the SCID (Structured Clinical Interview for DSM), delusion assessment scales, and questionnaires of social and occupational functioning.
Step 2: Verify Specifiers
ICD-11 allows additional specification of delusional disorder through subtypes based on predominant thematic content:
Persecutory Type: Delusions that the individual is being conspired against, deceived, spied on, or persecuted.
Erotomanic Type: Delusions that another person, usually of superior status, is in love with the individual.
Somatic Type: Delusions involving bodily functions or sensations, including infestations, deformities, or diseases.
Also document course characteristics: first episode versus recurrent, continuous versus episodic, and response to previous treatments when applicable.
Step 3: Differentiate from Other Codes
6A20 - Schizophrenia: The key difference is the presence of additional characteristic symptoms in schizophrenia. Patients with schizophrenia typically present with persistent auditory hallucinations, prominent negative symptoms (affective blunting, avolition, alogia), disorganized thinking or behavior, and broader functional deterioration. In delusional disorder, delusions occur in isolation without these additional symptoms.
6A21 - Schizoaffective Disorder: The fundamental difference is the presence of complete mood episodes (major depressive or manic) occurring simultaneously with psychotic symptoms of equivalent magnitude. In delusional disorder, there are no significant mood episodes, or delusions persist even in the absence of mood changes.
6A22 - Schizotypal Disorder: This condition is characterized by a persistent pattern of deficits in interpersonal relationships, cognitive or perceptual distortions, and eccentric behavior, but without true fixed delusions. Patients with schizotypal disorder may have ideas of reference or magical thinking, but these do not reach the unshakeable conviction characteristic of true delusions.
Step 4: Necessary Documentation
Adequate documentation should include:
Checklist of Mandatory Information:
- Detailed description of specific delusional content
- Date of onset and symptom duration
- Systematic assessment of absence of schizophrenic symptoms
- Assessment of functioning in multiple life areas
- Exclusion of general medical causes (complementary tests when indicated)
- Exclusion of substance use (toxicological history, tests when appropriate)
- Collateral information from family members or other informants
- Risk assessment (to self and others)
- Previous treatments and responses
- Specific functional impact related to delusions
Adequate Documentation: The medical record must clearly document the diagnostic reasoning, criteria met, differential diagnoses considered and excluded, and justification for the specific coding chosen.
6. Complete Practical Example
Clinical Case
Initial Presentation: A 48-year-old male patient, accountant, married, is brought to psychiatric consultation by his wife who is concerned about "strange" behaviors over the last 6 months. The patient is reluctant to attend, stating that "there is nothing wrong with me, I am just being cautious".
During the evaluation, the patient reveals, initially with hesitation and subsequently with increasing elaboration, that he discovered he is being monitored by work colleagues who wish to harm him professionally to assume his position. He describes having noticed "meaningful glances", conversations that cease when he approaches, and documents that were "subtly altered" on his computer.
In recent months, the patient began photographing his work environment daily to "document evidence", installed monitoring software on his personal computer, and avoids informal conversations with colleagues. He approached the human resources department three times in the last 4 months with complaints of "conspiracy", being repeatedly informed that there is no evidence of irregularities.
Evaluation Performed:
Mental Status Examination: Patient presents appropriately dressed and groomed, cooperative but cautious. Euthymic mood, affect congruent except when discussing his work concerns (becomes anxious and defensive). Thought content with persecutory delusional content, but thought process preserved - without disorganization, tangentiality, or circumstantiality. Denies auditory, visual, or other modality hallucinations. Denies depressive or manic symptoms. Absent insight regarding the pathological nature of his beliefs.
Functioning: The wife reports that, except for work-related issues, the patient maintains normal functioning. He continues to fulfill household responsibilities, maintains adequate family relationships (although has become "more withdrawn"), cares for himself appropriately, and maintains hobbies. There are no alterations in sleep or appetite unrelated to work anxiety.
Collateral History: The wife denies history of previous psychotic symptoms, substance use, or significant medical conditions. Denies current or past depressive or manic symptoms. Confirms that her husband's beliefs emerged gradually about 6 months ago following a minor work disagreement.
Complementary Evaluation: Laboratory tests (complete blood count, thyroid function, electrolytes) within normal limits. Denies use of medications, alcohol, or other substances.
Diagnostic Reasoning
The patient presents with a well-systematized persecutory delusion, persisting for 6 months, with unshakeable conviction despite repeated contrary evidence. The delusional content is specific and relatively circumscribed to the work environment.
Crucially, the patient does not present other psychotic symptoms characteristic of schizophrenia: no persistent auditory hallucinations, no negative symptoms (affective blunting, alogia, avolition), no thought or behavior disorganization, and no experiences of control or passivity.
Functioning is preserved in areas not directly related to the delusion. The patient maintains self-care, family relationships, cognitive capacities, and basic social skills. Behavioral changes (photographing environment, avoiding colleagues) relate directly to the delusional content.
There are no concomitant depressive or manic mood episodes. There is no evidence of general medical condition or substance use that could explain the symptoms.
Step-by-Step Coding
Criteria Analysis:
- ✓ Delusion present (persecution)
- ✓ Duration ≥ 3 months (6 months)
- ✓ Absence of mood episodes
- ✓ Absence of characteristic schizophrenic symptoms
- ✓ Functioning preserved except in areas related to delusion
- ✓ Not attributable to medical condition
- ✓ Not attributable to substances
Code Selected: 6A24 - Delusional Disorder
Complete Justification: The diagnosis of delusional disorder is established based on the presence of persistent persecutory delusion for 6 months, in the absence of other psychotic symptoms characteristic of schizophrenia, relatively preserved functioning, and exclusion of medical or substance-related causes. The presentation does not meet criteria for schizophrenia due to the absence of additional characteristic symptoms. Does not meet criteria for schizoaffective disorder due to the absence of significant mood episodes.
Complementary Codes: Additional coding may be considered for anxiety related to delusional content, if clinically significant and requiring specific intervention.
7. Related Codes and Differentiation
Within the Same Category
6A20 - Schizophrenia
When to use: Use 6A20 when the patient presents, in addition to possible delusions, two or more of the following symptoms for a significant period: persistent hallucinations (especially auditory), disorganization of thought, grossly disorganized or catatonic behavior, negative symptoms (affective blunting, alogia, avolition), or experiences of passivity and control.
Main difference: In schizophrenia, there is presence of multiple characteristic psychotic symptoms and typically broader functional deterioration. In delusional disorder, delusions occur in relative isolation, without the additional symptoms characteristic of schizophrenia, and functioning is preserved except in areas directly related to delusional content.
Differentiating example: A patient with persecutory delusions who also hears voices commenting on their behaviors, presents significant affective blunting and deterioration in self-care would receive a diagnosis of schizophrenia (6A20), not delusional disorder.
6A21 - Schizoaffective Disorder
When to use: Apply 6A21 when there is simultaneous presence of prominent psychotic symptoms and complete mood episodes (major depressive or manic) of equivalent magnitude and duration, occurring during the same phase of the illness.
Main difference: Schizoaffective disorder requires concomitant presence of psychotic symptoms and complete mood episodes. In delusional disorder, there are no significant mood episodes, or delusions clearly persist outside of any mood alterations.
Differentiating example: A patient with delusions of grandeur who also presents a complete manic episode with elevated mood, increased energy, decreased need for sleep and impulsivity would receive a diagnosis of schizoaffective disorder (6A21) or bipolar disorder with psychotic features, not delusional disorder.
6A22 - Schizotypal Disorder
When to use: Use 6A22 when there is a persistent and pervasive pattern of interpersonal deficits, cognitive or perceptual distortions and behavioral eccentricities, but without true fixed delusions or other clear psychotic symptoms.
Main difference: Schizotypal disorder is characterized by peculiar personality traits, ideas of reference (not true delusions), magical thinking and unusual perceptual experiences, but without the unshakeable conviction characteristic of true delusions. Delusional disorder involves genuine fixed delusions.
Differentiating example: A patient who believes they have weak telepathic abilities, feels uncomfortable in social situations, has vague and circumstantial thinking, but does not maintain fixed delusional conviction would receive a diagnosis of schizotypal disorder (6A22), not delusional disorder.
Differential Diagnoses
Obsessive-Compulsive Disorder: There may be overvalued beliefs about contamination, order or harm, but patients with OCD generally recognize that their concerns are excessive or irrational (preserved insight), unlike delusions where there is absolute conviction.
Body Dysmorphic Disorder: Involves excessive preoccupation with perceived defect in appearance, but typically there is some degree of fluctuating insight, unlike somatic delusion where conviction is unshakeable.
Paranoid Personality Disorder: Characterized by generalized distrust and suspicion, but without true fixed delusions. Suspicions are more diffuse and do not reach delusional conviction.
Dementias and Other Neurological Conditions: May present with secondary delusions, but there is clear evidence of global cognitive impairment or other neurological signs that are not present in primary delusional disorder.
8. Differences with ICD-10
In ICD-10, delusional disorder was coded as F22 - Persistent delusional disorders, with subdivisions including F22.0 (Delusional disorder), F22.8 (Other persistent delusional disorders) and F22.9 (Persistent delusional disorder, unspecified).
The main changes in ICD-11 include:
Structural Reorganization: ICD-11 integrated delusional disorder more cohesively within the category of "Schizophrenia or other primary psychotic disorders", with alphanumeric code 6A24, facilitating navigation and understanding of the relationships between different psychotic conditions.
More Specific Criteria: ICD-11 provides more detailed and operationalized definitions, more clearly specifying the minimum duration (typically 3 months), the necessary absence of characteristic schizophrenic symptoms, and the permissibility of perceptual disturbances related to the delusional theme.
Emphasis on Functioning: The new classification more explicitly emphasizes that functioning, affect, speech and behavior typically remain unaffected except in areas directly related to the delusion, facilitating differentiation of more deteriorating conditions.
Clearer Exclusions: ICD-11 specifies exclusions in greater detail, including general medical conditions and substance effects, with specific examples such as brain tumors and corticosteroids.
The practical impact of these changes includes greater diagnostic consistency among different professionals and regions, better differentiation of similar conditions, and more standardized documentation facilitating research and epidemiological tracking. The transition requires familiarization with the new criteria and codes, but offers a clearer framework for diagnosis and coding.
9. Frequently Asked Questions
How is delusional disorder diagnosed?
Diagnosis is established through comprehensive psychiatric evaluation including detailed clinical interview, mental status examination, and frequently information from family members or other informants. The clinician must identify the presence of delusions (fixed, false, and unshakeable beliefs) persisting for at least 3 months, systematically assess the absence of characteristic schizophrenic symptoms (persistent hallucinations, negative symptoms, disorganization), verify preserved functioning in areas unrelated to the delusion, and exclude medical or substance-related causes through clinical history, physical examination, and complementary tests when indicated. There are no specific laboratory or imaging tests to diagnose delusional disorder; diagnosis is fundamentally clinical.
Is treatment available in public health systems?
Treatment for delusional disorder is generally available in public health systems through mental health and psychiatry services. Specific access varies according to local organization of health services, but typically includes psychiatric outpatient care, antipsychotic medications (which frequently are part of essential medication lists), and in some cases psychotherapy. Patients can access services through primary health care units with referral to specialists, community mental health centers, or psychiatric hospital services when necessary. The availability of specific treatment modalities may vary, but basic treatment with antipsychotic medications is widely accessible.
How long does treatment last?
Delusional disorder typically requires prolonged treatment, often measured in years rather than months. The specific duration varies significantly among individuals depending on treatment response, symptom severity, and presence of risk factors for relapse. Many patients require maintenance treatment for an indefinite period to prevent recurrence of delusions. After initial treatment response (which may take several weeks to months), continuation is recommended for at least 12 months before considering gradual medication reduction, and even then only with careful monitoring. Premature discontinuation is associated with high relapse rates. Some patients require indefinite continuous treatment, while others may eventually discontinue medication with careful monitoring, although this is less common.
Can this code be used on medical certificates?
Yes, code 6A24 can be used on medical certificates when appropriate to document the condition that justifies leave or necessary accommodations. However, considerations of confidentiality and stigma should be weighed. In many situations, it may be appropriate to use more general terminology such as "psychiatric condition" or "mental health disorder" in documents that will be seen by employers or other non-medical parties, reserving the specific code for internal medical documentation. The decision should balance the need for adequate documentation with protection of patient privacy. When the code is used on certificates, it should be accompanied by information about specific functional limitations and accommodation needs, rather than just the diagnosis alone.
Do patients with delusional disorder recognize that they are ill?
Typically not. The absence of insight (recognition of the condition as pathological) is a central characteristic of delusional disorder. Patients maintain absolute conviction in the veracity of their delusional beliefs and rarely seek treatment spontaneously. They are frequently brought for evaluation by concerned family members or after social, occupational, or legal consequences of behaviors related to the delusions. This lack of insight represents a significant challenge for treatment engagement and medication adherence. Therapeutic approaches should consider this characteristic, initially focusing on establishing therapeutic alliance and addressing practical consequences of the delusions rather than directly confronting the beliefs. With successful treatment, some patients develop partial insight, although this varies considerably.
What is the difference between delusional disorder and paranoia?
"Paranoia" is a broad term referring to distrust, suspicion, or excessive fear of persecution, and can occur in multiple conditions or even as a personality trait. Delusional disorder is a specific psychiatric diagnosis characterized by persistent delusions (which may, but do not necessarily, have persecutory/paranoid content). Not all delusions in delusional disorder are paranoid—they may be erotomania, somatic, grandiose, among others. Conversely, not all paranoia constitutes delusional disorder—it can occur in paranoid personality disorder (without true delusions), paranoid schizophrenia (with additional symptoms), or as a symptom of other conditions. Delusional disorder requires specific diagnostic criteria including duration, absence of other psychotic symptoms, and relatively preserved functioning.
Is delusional disorder hereditary?
There is evidence of a genetic component in delusional disorder, although less studied than in schizophrenia. Family studies suggest slightly increased risk in first-degree relatives of individuals with delusional disorder, but absolute risk remains low. Genetic factors probably interact with environmental factors, life experiences, and personality characteristics in the development of the condition. Family history of psychotic disorders or delusional disorder specifically may be a risk factor, but most individuals with family history do not develop the condition, and many patients with delusional disorder have no identifiable family history. Hereditability is not deterministic, and multiple factors contribute to the development of the condition.
Are people with delusional disorder dangerous?
The majority of individuals with delusional disorder are not violent. However, certain types of delusions may be associated with increased risk of problematic behaviors. Persecutory delusions may lead to defensive or confrontational behaviors. Erotomania delusions may result in pursuit or harassment of the object of the delusion. Jealousy delusions may be associated with violence against partners perceived as unfaithful. Risk assessment is an essential component of clinical evaluation, considering specific content of the delusions, history of violent behavior, access to means, presence of substance use, and protective factors. When risk is identified, appropriate interventions include intensive treatment, possible hospitalization, and in some cases involvement of protective systems. The vast majority of patients, with appropriate treatment, do not represent significant danger.
Conclusion:
Delusional disorder (ICD-11: 6A24) represents a distinct psychiatric condition characterized by persistent delusions in the absence of other prominent psychotic symptoms and with relatively preserved functioning. Correct coding requires detailed understanding of diagnostic criteria, careful differentiation of similar conditions, and adequate documentation. The transition from ICD-10 to ICD-11 brought important refinements that facilitate more precise and consistent diagnosis. Health professionals should familiarize themselves with these updated criteria to ensure appropriate coding, facilitating adequate treatment, clinical research, and epidemiological tracking of this challenging but treatable condition.
External References
This article was prepared based on reliable scientific sources:
- 🌍 WHO ICD-11 - Delusional Disorder
- 🔬 PubMed Research on Delusional Disorder
- 🌍 WHO Health Topics
- 📋 NICE Mental Health Guidelines
- 📊 Clinical Evidence: Delusional Disorder
- 📋 Ministry of Health - Brazil
- 📊 Cochrane Systematic Reviews
References verified on 2026-02-02