disorder. The delusions should occur in the absence
of prominent mood symptoms and should not be the
result of substance intoxication or withdrawal or of
general medical conditions.Psychotic Disorder Due to a General Medical
Condition. This is characterized by prominent delusions
or hallucinations that arose during or shortly after and
apparently in response to the physiological result of a
general medical illness, which has been confirmed by
history, physical examination, or laboratory findings.
The symptoms should not occur only during periods of
clouded consciousness (i.e., delirium). Two subtypes are
recognized, With Delusions and With Hallucinations,
based on which psychotic symptoms are predominant.Substance-Induced Psychotic Disorder. This is identi-
cal to Psychotic Disorder Due to a General Medical
Condition, except that history, physical examination,
or laboratory findings indicate that the symptoms arose
during or shortly after and apparently in response to
substance intoxication or withdrawal. Two subtypes
are recognized, With Onset During Intoxication and
With Onset During Withdrawal.Epidemiology
The lifetime prevalence of psychotic disorders in the
general population is about 3% to 4%; the most com-
mon psychotic disorder is schizophrenia, with a
lifetime prevalence of about 1% to 2%. Psychotic
symptoms occur with much greater frequency; the
lifetime prevalence of isolated delusions of hallucina-
tions may be as high as 4% to 8%, and the lifetime
prevalence of any psychotic symptom may be as high
as 10% to 20%. The prevalence of psychotic disorders
apparently varies little across nations, although within
various nations, they may be diagnosed more often
among members of ethnocultural minority groups and
among recent immigrants. There is evidence of a
small gender difference, with slightly higher rates
among men than among women.Etiology
Considerable research indicates the importance of neu-
robiological factors in the etiology of psychotic disor-
ders, most likely as vulnerabilities or predisposing
factors. Behavioral genetic studies indicate that psy-
chotic disorders, and especially schizophrenia, are sub-
stantially heritable; however, molecular genetic studies
have not been successful in isolating which genes, oreven which chromosomes, are involved. The strength
of the genetic contribution seems to vary as a function
of the type of schizophrenia, with the strongest genetic
loading associated with negative and disorganization
symptoms. Many behavior geneticists agree that a
polygenetic model is most likely, although there is also
some support for a multifactorial model in which spe-
cific genes produce major effects and polygenes poten-
tiate or insulate against the effects of the specific genes.
Other studies have found that psychotic disorders are
associated with a history of pregnancy and birth com-
plications, including increased rates of maternal
influenza in the second trimester, smoking and nutri-
tional deprivation, and mother-child Rh incompatibility
during pregnancy; obstetrical complications during
delivery; and congenital abnormalities evident follow-
ing delivery. Neuroimaging and postmortem studies
have found an increased rate of structural brain abnor-
malities in people with psychotic disorders, as well as
in their first-degree biological relatives, including
enlarged ventricular and sulcal spaces; decreased brain
volume, especially in the frontal and temporal regions,
thalamus, amygdale, and hippocampus; reduced inter-
region connectivity; cytohistological abnormalities in
the prefrontal and temporal regions, thalamus, hip-
pocampus, and parahippocampal gyrus; and changes in
regional activity during performance of cognitive tasks.
Pharmacological studies indicate that disturbances
of the dopaminergic neurotransmitter system in the
brain (e.g., elevated frequency and activity of dopamine
receptors) may be related to positive psychotic symp-
toms, whereas the serotonergic and glutamate systems
may be related to both positive and negative symptoms.
Psychosocial factors may also be important in the
etiology of psychotic disorders, most likely as triggers
or precipitating factors. Life event studies indicate that
active phases of psychotic disorders—both first
episodes and recurrences—may occur shortly after, and
apparently in reaction to, major life stressors. Also, a
high level of negative expressed emotion in close per-
sonal relationships is associated with increased risk
for development of psychotic disorders, as well as the
recurrence of active phases. Both these factors, how-
ever, may be of limited importance in the absence of a
neurobiological vulnerability or predisposition.Treatment
Pharmacological treatments have been used for more
than 50 years during the active phase of psychotic
disorders. In the 1950s through the 1970s, the mechanismPsychotic Disorders——— 653P-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 653