The essential characteristic of this condition is the presence of non-bizarre delusions that last for at least a month. None of the other symptoms of schizophrenia are present. A diagnosis of delusional disorder may not be made if the patient is experiencing hallucinations unless they are hallucinations of only touch and/or smell that are directly related to the patient's dominant delusion. In addition, the delusion cannot be due to drug use or another disease such as Alzheimer's disease, dementia, or some other identifiable cause.
What psychiatrists consider non-bizarre delusions are often considered quite bizarre by non-psychiatrists. The DSM-IV provides two examples of non-bizarre delusions that might affect someone with delusional disorder:
A delusion of infestation related to a belief that the body is infested with insects; a tactile hallucination
A delusional belief that one is emitting a foul odor; an olfactory delusion
These are considered non-bizarre because they are possible, even if they are unlikely. Examples of bizarre delusions are the belief that others are controlling your thoughts or that you have been chosen by a supreme being to solve humankind's problems.
Criteria for an Accurate Diagnosis of Delusional Disorder
The presence of non-bizarre delusions for at least one month
No other symptoms of schizophrenia
Hallucinations of touch and smell may be present if related to the theme of the delusion
Aside from the direct consequences of the delusion, the patient's life is not affected in any way; in other words, intelligence and ability to function in society are normal
Depression, if present, does not last as long as the delusion has been present
The disorder cannot be traced to any medication, drug, or medical condition
Adapted from the DSM-IV.
Some people with delusional disorder do not function well, depending on the nature of their delusions. If the delusion is one that makes the patient afraid to leave his home for fear of his safety, he may not be able to work or maintain a social life. Again, this poor psychosocial functioning must be due to the delusion and not, for example, to unrelated social withdrawal and the apathy often seen in people with schizophrenia.
Most psychiatrists find that when delusional disorder is present, social relationships, including marriage, are more likely to suffer than is the patient's ability to work or reason. If the delusion does not figure closely into the subject of conversation or the task someone is working on, the person with delusional disorder can function well.
Prominent Types of Delusions
The subtype of delusional disorder is determined by the nature of the delusion. The erotomanic subtype, for example, is diagnosed when a person believes that someone else, often a person of higher social status, is in love with the patient. Lust often plays less of a role in the delusion than does the notion of intense romantic love, an unrealistic idealized connection between two souls. The object of desire is often someone the patient looks up to, such as a celebrity or someone who is obviously successful. It can be someone the patient doesn't know but believes has admirable traits and reciprocates the feeling of devotion.
If a female has an erotomanic delusion, you are likely to find her in a clinic. Men with this disorder more frequently come to the attention of police. While both sexes may try to contact the objects of their affection by repeatedly calling, writing, visiting, and stalking, males tend to be more aggressive in their pursuit.
There are exceptions to the generalized profile of this subtype, of course. For example, some patients may not tell anyone, not even the object of the delusion, about their obsession. The more aggressive pursuer who won't take no for an answer, however, is much more common.
There are several other types of delusions:
A grandiose delusion elevates the importance of someone in his own estimation. This person is convinced he has special or unique knowledge, accomplishments, social connections, or talent. In an extreme case, a person may be convinced he is someone else, a person who is well-known. To explain the presence of the real celebrity, the patient insists that that person is a double or an imposter.
A jealous delusion has as its key theme the imagined infidelity of a lover or spouse. This type of disorder can be traumatic for the partner, who can be subjected to unremitting and unfounded accusations based on innocuous evidence. The ill person may initiate investigations of the partner, follow her, or threaten her with violence.
Persecutory delusions have several features in common with paranoid thinking. The DSM-IV defines this subtype as a person who believes he is “being conspired against, cheated, spied on, followed, poisoned or drugged, maliciously • maligned, harassed, or obstructed in the pursuit of long-term goals.” The person with this disorder may repeatedly write to authorities seeking justice for imagined wrongs. When satisfaction fails to come, the patient's bitterness, anger, and frustration may cause him to attack his imagined enemies.
Somatic delusions are fixated on the body. They can typically be divided into three general categories. The first is the most common: the belief that the patient's skin or a body orifice emits an unpleasant odor. The second imagines an infestation of insects or parasites somewhere in or on the body. The third group concerns the body's appearance or function. Despite the evidence in the mirror, people with this delusion are convinced that a body part is malformed, hideously unattractive, or not functioning properly.
A patient will be diagnosed as having a mixed subtype if one subtype among the previous five categories is not dominant over the others.
A diagnosis of an unspecified subtype is made if a patient's delusion doesn't fit any of the other subtypes.