Delusional disorder is a mental illness in which a person has delusions, but with no accompanying prominent hallucinations, thought disorder, mood disorder, or significant flattening of affect. Delusions are a specific symptom of psychosis. Delusions can be bizarre or non-bizarre in content; non-bizarre delusions are fixed false beliefs that involve situations that could occur in real life, such as being harmed or poisoned. Apart from their delusion or delusions, people with delusional disorder may continue to socialize and function in a normal manner and their behavior does not necessarily generally seem odd. However, the preoccupation with delusional ideas can be disruptive to their overall lives.For the diagnosis to be made, auditory and visual hallucinations cannot be prominent, though olfactory or tactile hallucinations related to the content of the delusion may be present. The delusions cannot be due to the effects of a drug, medication, or general medical condition, and delusional disorder cannot be diagnosed in an individual previously properly diagnosed with schizophrenia. A person with delusional disorder may be high functioning in daily life. Recent and comprehensive meta-analyses of scientific studies point to an association between a deterioration in aspects of IQ in psychotic patients, in particular perceptual reasoning.According to German psychiatrist Emil Kraepelin, patients with delusional disorder remain coherent, sensible and reasonable.
The incidence of first admissions for delusional disorder is lower, from 0.001 to 0.003%.Delusional disorder tends to appear in middle to late adult life, and for the most part first admissions to hospital for delusional disorder occur between age 33 and 55. It is more common in women than men, and immigrants seem to be at higher risk. Criticism
In some situations the delusion may turn out to be true belief. For example, in delusional jealousy, where a person believes that the partner is being unfaithful (in extreme cases perhaps going so far as to follow the partner into the bathroom, believing the other to be seeing a lover even during the briefest of separations), it may actually be true that the partner is having sexual relations with another person. In this case, the delusion does not cease to be a delusion because the content later turns out to be verified as true or the partner actually chose to engage in the behavior of which they were being accused. In other cases, the delusion may be mistakenly assumed to be false by a doctor or psychiatrist assessing the belief, just because it seems to be unlikely, bizarre or held with excessive conviction. Psychiatrists rarely have the time or resources to check the validity of a persons claims leading to some true beliefs to be erroneously classified as delusional. This is known as the Martha Mitchell effect, after the wife of the attorney general who alleged that illegal activity was taking place in the White House.