102 Schizophrenia Spectrum and Other Psychotic Disorders
and persons with schizophrenia, including ev idence from neuroimaging, neuropatholog-
ical, and neurophysiological studies. Differences  are also evident in cellular architecture,
white matter connectivity, and gray matter volume in a vari ety of regions such as the pre-
frontal and temporal cortices. Reduced overall brain volume has been observed, as well as
increased brain volume reduction with age. Brain volume reductions with age are more
pronounced in individuals with schizophrenia than in healthy individuals. Finally, indi-
viduals with schizophrenia appear to differ from individuals withou t the disorder in eye-
tracking and electrophysiological indices.
Neurological soft signs common in individuals with schizophrenia include impairments
in motor coordination, sensory integration, and motor sequencing of complex movements;
left-right confusion; and disinhibition of associated mo vements. In addition, minor phys-
ical anomalies of the face and limbs may occur.
Prevalence
The lifetime prevalence of schizophrenia appears to be approximately 0.3%–0.7%, al-
though there is reported variation by race/ethnicity, across countries, and by geographic
origin for immigrants and children of immigr ants. The sex ratio differs across samples and
populations: for example, an emphasis on nega tive symptoms and longer duration of dis-
order (associated with poorer outcome) show s higher incidence rates for males, whereas
definitions allowing for the inclusion of more mood symptoms and brief presentations
(associated with better outcome) show  equivalent risks for both sexes. 
Development and Course
The psychotic features of schizophrenia typically emerge between the late teens and the
mid-30s; onset prior to adolescence is rare. The peak age at onset for the first psychotic ep-