Invitation to Psychology

408 Chapter 11 Psychological Disorders

to a risk in the general population of only about

1 percent (see Figure 11.4). Researchers all over

the world are trying to identify the genes that

might be involved in specific symptoms, such

as hallucinations, sensitivity to sounds, cognitive

impairments, and social withdrawal (Desbonnet,

Waddington, & O’Tuathaigh, 2009; Tomppo

et  al., 2009). However, efforts to find the criti-

cal genes in schizophrenia have been difficult

because several appear to be involved, and those

are linked not only to schizophrenia but also—as

we noted previously—to bipolar disorder, depres-

sion, and other mental disorders (Walker &

Tessner, 2008).

2

Prenatal problems or birth complications.

Damage to the fetal brain significantly

increases the likelihood of schizophrenia later in

life. Such damage may occur if the mother suf-

fers from malnutrition; schizophrenia rates rise

during times of famine (St. Clair et al., 2005).

Damage may also occur if the mother gets the

flu virus during the first four months of prenatal

development, which triples the risk of schizo-

phrenia (Brown et al., 2004; Mednick, Huttunen,

& Machón, 1994). And it may occur if there

are complications during birth that injure the

baby’s brain or deprive it of oxygen (Cannon

et al., 2000). Other nongenetic prenatal factors

that increase the child’s risk of schizophrenia

include maternal diabetes and emotional stress,

having a father older than age 55, birth during a

tend to have reduced volumes of gray matter in

the prefrontal cortex and temporal lobes; abnor-

malities in the hippocampus; and abnormalities in

neurotransmitters, neural activity, and communi-

cation between neurons in areas involving cogni-

tive functions such as memory, decision making,

and emotional processing (Karlsgodt, Sun, &

Cannon, 2010). Most individuals with schizo-

phrenia also show enlargement of the ventricles,

spaces in the brain that are filled with cerebro-

spinal fluid (see Figure 11.3) (Heinrichs, 2005).

And they are more likely than individuals with-

out schizophrenia to have abnormalities in the

thalamus, the traffic-control center that filters

sensations and focuses attention (Andreasen et al.,

1994; Gur et al., 1998). Many have deficiencies

in the auditory cortex and Broca and Wernicke’s

areas, all involved in speech perception and pro-

cessing; these might explain the nightmare of

voice hallucinations.

Currently, researchers have identified three

contributing factors in this disorder:

1

genetic predispositions. Schizophrenia is

highly heritable. A person has a much greater

risk of developing the disorder if an identical

twin develops it, even if the twins are reared

apart (Gottesman, 1991; Gottesman et al., 2010;

Heinrichs, 2005). Children with one schizo-

phrenic parent have a lifetime risk of 7 to 12 per-

cent, and children with two schizophrenic parents

have a lifetime risk of 27 to 46 percent, compared

FigURE 11.3 Schizophrenia and the Brain

People with schizophrenia are more likely to have enlarged ventricles (spaces) in the brain. These MRI scans of

28-year-old male identical twins show the difference in the size of ventricles between the twin without schizophrenia

(left) and the one with schizophrenia (right).