A person with Delusional Disorder will have the presence of delusions for at least one month. Daily functioning is usually not impaired (aside from the impact of the delusions) and the person's behavior is not odd or bizarre in an obvious way. There are either no hallucinations or hallucinations are not prominent. Personality is usually preserved and there is no disorganized behavior or grossly confused thought processes as in Schizophrenia. Delusions are often of persecution, but may also include infidelity, grandiosity, somatic change, or erotomania. Delusions are usually specific to a certain person, a given place, time, or activity.

The delusions are usually well organized with elaborate reasons for what the individual is doing. The delusions are generally grandiose.

These patients generally do not seek out treatment on their own; they are usually identified by a family member. Diagnosis is difficult because these individuals are so mistrustful. The therapist has to be careful not to become "the enemy".

When dealing with Delusional Disorder, the theoretical approach is usually supportive. It is most important to gain the trust of the individual through a neutral and accepting attitude. These patients are extremely sensitive to criticism, making rapport building very difficult.

The goals associated with Delusional Disorder are to conduct an assessment and address any safety issues as well as establish a working alliance. When doing the assessment you must be cautious. The patient may be testing you to determine whether you should be perceived as dangerous. You will assess the client to find out if he/or she poses a danger to self or others and take any necessary action to ensure safety. Intervention is a very gradual process. Engage the patient in his/or her world; get inside to really understand things from the patient's perspective. With empathic and sensitive involvement, you may be able to slowly allow the patient to see things from your perspective.

Antipsychotic medication may be helpful to take the "power" out of the delusion. Antidepressants may also have some positive effects. Medication compliance is very important and should be monitored as well.

Two unusual conditions have been observed in patients with Delusional Disorder: Capgras Syndrome, in which a patient believes that a person close to him/or her has been replaced by a double, and Fregoli Syndrome where the patient identifies various people encountered as "psychologically identical" to a familiar person. With Fregoli Syndrome, the patient acknowledges that there is no physical similarity to the other person but continues to insist that they are identical.