92 Schizophrenia Spectrum and Other Psychotic Disorders
dividual’s belief of being conspired against,  cheated, spied on, followed, poisoned, mali-
ciously maligned, harassed, or obstructed in the pursuit of long-term goals. Small slights
may be exaggerated and become the focus of a delusional system. The affected individual
may engage in repeated attempts to obtain sat isfaction by legal or legislative action. Indi-
viduals with persecutory delusions are often resentful and angry and may resort to vio-
lence against those they believe are hurting them. In somatic type,  the central theme of the
delusion involves bodily functi ons or sensations. Somatic de lusions can occur in several
forms. Most common is the belief that the indi vidual emits a foul odor ; that there is an in-
festation of insects on or in the skin; that ther e is an internal parasite; that certain parts of
the body are misshapen or ugly; or that parts of the body are not functioning.
Diagnostic Features
The essential feature of delusional disorder is the presence of one or more 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 presen tation that met Criterion A for schizophre-
nia (Criterion B). Apart from the direct impact  of the delusions, impairments in psychoso-
cial functioning may be more circumscribed th an those seen in other psychotic disorders
such as schizophrenia, and behavior is not obviously bizarre or odd (Criterion C). If mood
episodes occur concurrently with the delusions , the total duration of these mood episodes
is brief relative to the total duration of the delusional periods (Criterion D). The delusions