The essential feature of Delusional Disorder is the presence of one or more non bizarre delusions that persist for at least 1 month (Criterion A). A diagnosis of Delusional Disorder is not given if the individual has ever had a symptom presentation that met Criterion A for Schizophrenia Criterion B). Auditory or visual hallucinations, if present, are not prominent. Tactile or olfactory hallucinations may be present (and prominent) if they are related to the delusional theme (e.g., the sensation of being infested with insects associated with delusions of infestation, or the perception that one emits a foul odor from a body orifice associated with delusions of reference). Apart from the direct impact of the delusions, psychosocial functioning is not markedly impaired, and behavior is neither obviously odd nor bizarre (Criterion C). If mood episodes occur concurrently with the delusions, the total duration of these mood episodes is relatively brief compared to the total duration of the delusional periods (Criterion D). The delusions are not due to the direct physiological effects of a substance (e.g., cocaine) or a general medical condition (e.g., Alzheimer's disease, systemic lupus erythematosus) (Criterion E).
Although the determination of whether delusions are bizarre is considered to be especially important in distinguishing between Delusional Disorder and Schizophrenia, "bizarreness" may be difficult to judge, especially across different cultures. Delusions are deemed bizarre if they are clearly implausible, not understandable, and not derived from ordinary life experiences (e.g., an individual's belief that a stranger has removed his or her internal organs and replaced them with someone else's organs without leaving any wounds or scars). In contrast, nonbizarre delusions involve situations that can conceivably occur in real life (e.g., being followed, poisoned, infected, loved at a distance, or deceived by one's spouse or lover).
Psychosocial functioning is variable. Some individuals may appear to be relatively unimpaired in their interpersonal and occupational roles. In others, the impairment may be substantial and include low or absent occupational functioning and social isolation. When poor psychosocial functioning is present in Delusional Disorder, it arises directly from the delusional beliefs themselves. For example, an individual who is convinced that he will be murdered by "Mafia hit men" may quit his job and refuse to leave his house except late at night and only when dressed in clothes quite different from his normal attire. All of this behavior is an understandable attempt to prevent being identified and killed by his p resumed assassins. In contrast, poor functioning in Schizophrenia may be due to both positive and negative symptoms (particularly avolition). Similarly, a common characteristic of individuals with Delusional Disorder is the apparent normality of their behavior and appearance when their delusional ideas are not being discussed or acted on. In general, social and marital functioning are more likely to be impaired than intellectual and occupational functioning.
The type of Delusional Disorder may be specified based on the predominant delusional theme:
Erolomanic Type. This subtype applies when the central theme of the delusion is that another person is in love with the individual. The delusion often concerns idealized romantic love and spiritual union rather than sexual attraction. The person about whom this conviction is held is usually of higher status (e.g., a famous person or a superior at work), but can be a complete stranger. Efforts to contact the object of the delusion (through telephone calls, letters, gifts, visits, and even surveillance and stalking) are common, although OCC.1- occasionally the person keeps the delusion secret. Most individuals with this subtype in clinical samples are female; most individuals with...