Delusional Disorder 93
schizophrenia. Delusional disorder has a significant familial relationship with both
schizophrenia and schizotypal personality diso rder. Although it can occur in younger age
groups, the condition may be more  prevalent in older individuals.
Culture-Related Diagnostic Issues
An individual’s cultural and religious backgr ound must be taken into  account in evaluat-
ing the possible presence of delusional di sorder. The content of delusions also varies
across cultural contexts.
Functional Consequences of Delusional Disorder
The functional impairment is usually more ci rcumscribed than that seen with other psy-
chotic disorders, although in some cases, the impairment may be substantial and include
poor occupational functioning and social isola tion. When poor psychosocial functioning is
present, delusional beliefs themselves ofte n play a significant role. A common character-
istic of individuals with delusional disorder is the apparent normality of their behavior
and appearance when their delusional idea s are not being discussed or acted on. 
Differential Diagnosis
Obsessive-compulsive and related disorders. If an individual wi th obsessive-compul-
sive disorder is completely convinced that his or her obsessive-comp ulsive disorder beliefs
are true, then the diagnosis of obsessive-compulsive disorder, with absent insight/delu-
sional beliefs specifier, should be given rath er than a diagnosis of delusional disorder.
Similarly, if an individual with body dysm orphic disorder is completely convinced that
his or her body dysmorphic disorder beliefs are true, then the diagnosis of body dysmor-
phic disorder, with absent insight/delusional beliefs specifier, should be given rather than
a diagnosis of delusional disorder. 
Delirium, major neurocognitive disorder, psychotic disorder due to another medical con-