Psychotic Disorder Due to Another Medical Condition 117
been estimated to range from 0.21% to 0.54%. When the prevalence findings are stratified
by age group, individuals older than 65 years have a significantly greater prevalence of
0.74% compared with those in younger age grou ps. Rates of psychosis also vary according
to the underlying medical condition; cond itions most commonly  associated with psy-
chosis include untreated endocrine and metabo lic disorders, autoim mune disorders (e.g.,
systemic lupus erythematosus, N-methyl- D-aspartate (NMDA) receptor autoimmune en-
cephalitis), or temporal lobe epilepsy. Psycho sis due to epilepsy has been further differ-
entiated into ictal, postictal, and interictal  psychosis. The most common of these is postictal
psychosis, observed in 2%–7.8% of epilepsy patients. Among older individuals, there may
be a higher prevalence of the disorder in fe males, although additional gender-related fea-
tures are not clear and vary considerably with  the gender distributions of the underlying
medical conditions.
Development and Course
Psychotic disorder due to another medical condition may be a single transient state or it
may be recurrent, cycling with  exacerbations and remissions of the underlying medical
condition. Although treatment of the underlyi ng medical condition often results in a res-
olution of the psychosis, this is not always  the case, and psychotic symptoms may persist
long after the medical event (e.g ., psychotic disorder due to fo cal brain injury). In the con-
text of chronic conditions such as multiple sc lerosis or chronic interictal psychosis of epi-
lepsy, the psychosis may assume a long-term course.
The expression of psychotic disorder due to  another medical cond ition does not differ