Abnormal Psychology

Schizophrenia and Other Psychotic Disorders 541

Neurological Factors in Schizophrenia

Perhaps more than for any other psychological disorder, neurological factors play

a crucial role in the development of schizophrenia. These factors involve brain

systems, neural communication, and genetics.

Brain Systems

People who have schizophrenia have abnormalities in the struc-

ture and function of their brains. Early research on this topic came

from autopsy studies in which researchers compared the brains

of people who had schizophrenia with those of people who did

not (Rosanoff, 1914; Southard, 1910). These researchers found

that the brains of people who had schizophrenia were atrophied

(shrunken) relative to the brains of people without the disorder.

Neuroimaging studies have since documented more specifi c differ-

ences in brain structure and function between those with schizo-

phrenia and those who do not have the disorder.

The most striking example of a structural abnormality in the

brains of people with schizophrenia is enlarged ventricles, which are

cavities in the center of the brain that are fi lled with cerebrospinal

fl uid (Vita et al., 2006). Larger ventricles means that the size of the

brain itself is reduced. This reduction in size is especially signifi cant

for people with schizophrenia because, in general, even before devel-

oping the disorder, they have brains that are smaller than normal.

This is true, in part, because their brains never grew to “full” size.

In addition, research suggests that schizophrenia causes parts of the

brain to shrink (DeLisi et al., 1997; Gur, Ragland, & Gur, 1997;

Rapoport et al., 1999).

One possible reason for the differences in brain structure (and brain function-

ing) between those who have schizophrenia and those who do not could be effects

of the medications used to treat schizophrenia—and not the disorder itself. With

the development of neuroimaging techniques, scientists began to address this pos-

sibility. Researchers used longitudinal studies to follow people from the time of

their fi rst schizophrenic episode. Such studies have shown that even at the time

of their fi rst episode, people who have schizophrenia have smaller overall brain

volume and less cerebral cortex than people who have no known risk of develop-

ing schizophrenia (Velakoulis et al., 1999). In fact, the less cortical matter pa-

tients had, the more poorly they fared 2 years after their fi rst episode (Cahn et al.,

2002). Thus, these abnormalities in brain structure are not primarily a result of

taking medication.

In 1981, the Genain sisters, then 51 years old, returned to NIMH for a 3-month

evaluation; during that time they were taken off their medications. CT scans of

the quads showed similar brain abnormalities in all four sisters (Mirsky & Quinn,

1988). However, even though they were basically genetically identical, their perfor-

mance on neuropsychological tests varied: Nora and Hester showed more evidence

of neurological diffi culties, and they were more impaired in their daily functioning

when not taking medication. Thus, once again, we see that genes are not destiny

and that brain function cannot be considered in isolation. The brain is a mecha-

nism, but how it performs depends in part on how it is “programmed” by learning

and experience—which are psychological factors.

In the following sections, we consider the likely role of the following brain

abnormalities: a frontal lobe defect, an impaired temporal lobe and thalamus, an

abnormal hippocampus, and abnormal interactions among brain areas. We then

turn to possible causes of such abnormalities in the brain, considering the effects of

the mother’s diet or illness, as well as early oxygen deprivation. Finally, we examine

possible “biological markers”; telltale neurological, bodily, or behavioral signs that

may indirectly reveal that a person is vulnerable to developing schizophrenia.

These brain scans of identical twins show, for one

of them, the enlarged ventricles that typically are

associated with schizophrenia. The twin on the

right has schizophrenia, the twin on the left

does not.

Joe McNally/Getty Images