A delusion is a fixed false belief based on an inaccurate interpretation of an external reality despite evidence to the contrary. Cultural beliefs also impact the content of delusions. An individual’s cultural beliefs merit consideration before coming to the diagnosis. The belief is not congruent with one’s culture or subculture, and almost everyone else knows it to be false. Other than the delusions(s) the functionality is not impacted, and behavior is not obviously bizarre. There may be social isolation. A unique finding is apparent normal psychological functioning and appearance when not discussing the specific delusion.
Persecutory type: Persecutory – The central theme is being conspired against, attacked, harassed, obstructed in the pursuit of long-term goals. This is one of the most common types of delusions and patients can be anxious, irritable, aggressive, or even assaultive – some patients may be litigious.
Jealous type: Delusional jealousy – That one’s sexual partner is unfaithful. Also known as “Othello syndrome” this type is more common in males. It can sometimes correlate with suicidal or homicidal ideations, and hence safety is an important consideration in evaluation and management.
Erotomanic type: Erotomanic – A delusion that another person, more frequently someone of higher status is in love with the individual. Also known as “psychose passionelle”. These patients are usually socially withdrawn, dependent, sexually inhibited with a poor level of social and/or occupational functioning. “Paradoxical conduct” is an important characteristic wherein all denials of affection are rationalized as affirmations. Males with this type of delusion can be more aggressive.
Somatic type: Somatic – These involve bodily functions and sensations. Also called monosymptomatic hypochondriacal psychosis and the reality impairment is severe. The patient is unarguably convinced of the severity of the symptoms. The most common type of somatic delusions is that of infestation example with parasites, body dysmorphic delusion, and of body odor or halitosis. These patients also have anxiety and nervousness.
Grandiose type: Grandiose – A conviction of great talent, discovery, inflated self-worth, power, knowledge, or relationship with someone famous or deity. Also known as megalomania are notable for increased self-importance.
Mixed type: Mixed – No single theme is prevalent. Patients have two or more delusional themes.
Unspecified type: Sometimes a predominant delusion cannot be identified. Capgras syndrome is a delusional syndrome where there is a belief that a known person has been replaced by an impostor. Cotard syndrome is when a patient believes he has lost his possessions, status, and even bodily organs.
Frequent delusions are also:
Bizarre – A delusion involving a phenomenon that is impossible, not understandable, and unrelated to normal life.
Thought broadcasting – Delusion that one’s thought is projected and perceived by others.
Thought insertion – A delusion that one’s thought is not one’s own but inserted into their mind by an external source or entity.
Delusional disorder is relatively rare, has a later age of onset as compared to schizophrenia, and does not show a gender predominance. The patients are also relatively stable. The exact cause of the delusional disorder is unknown.
Delusional disorder, DSM criteria:
The presence of one (or more) delusions with a duration of 1 month or longer (A).
Criterion A for schizophrenia has never been met. Criterion A for schizophrenia: Two (or more) of the following, each present for a significant portion of time during a 1-month period (or less if successfully treated) (A):
- delusions
- hallucinations
- disorganized speech (e.g., frequent derailment or incoherence)
- grossly disorganized or catatonic behavior
- negative symptoms (i.e., diminished emotional expression and avolition)
Note: Tactile and olfactory hallucinations may be present in delusional disorder if they are related to the delusional theme. Hallucinations, if present, are not prominent and are related to the delusion theme (e.g., the sensation of being infested with insects associated with delusions of infestation (B).
Apart from the impact of the delusion(s) or its ramifications, functioning is not markedly impaired and behavior is not obviously odd or bizarre (C).
If mood episodes have occurred concurrently with delusions, their total duration has been brief relative to the duration of the delusional periods (D).
The disturbance is not attributable to the physiological effects of a substance or another medical condition and is not better explained by another mental disorder, such as body dysmorphic disorder or obsessive-compulsive disorder (E).