Delusional disorder is characterized by nonbizarre delusions without other psychotic symptoms. It is rare, its course is chronic, and treatment is supportive.

Epidemiology

This disorder is rare, with a prevalence of <0.05%. Generally, onset is in middle to late life; it affects women more often than men. Its course is chronic and unremitting.

Etiology

The etiology is unknown. Often, psychosocial stressors appear to be etiologic, for example, following migration. In migration psychosis, the recently immigrated person develops persecutory delusions. Many patients with delusional disorder have a paranoid character premorbidly. Paranoid personality disorder has been found in families of patients with delusional disorder.

Clinical Manifestations

History and Mental Status Examination
This disorder is characterized by well-systematized non bizarre delusions about things that could happen in real life (such as being followed, poisoned, infected, loved at a distance, having a disease, being deceived by one’s spouse or significant other). The delusions must be present for at least I month. Other than the delusion, the patient’s social adjustment may be normal.

The patient must not meet criteria for schizophrenia. Any mood disorder must be brief relative to the duration of the illness. The DSM-IV recognizes seven subtypes of delusional disorder (Table 1-5).

Differential Diagnosis

It is important to rule out other psychiatric or medical illnesses that could have caused the delusions. Thereafter, delusional disorder must be distinguished from major depression with psychotic features, mania, schizophrenia, and paranoid personality.

Management

Trials of antipsychotics are appropriate but are often ineffective. The primary treatment is psychotherapy, taking care to neither support nor refute the delusion but to maintain an alliance with the patient.

Without such an alliance, most patients fall out of treatment; with an alliance, over time, the patient may relinquish the delusions.