Abnormal Psychology

Dissociative and Somatoform Disorders 357

the body, and as we shall see, both involve catastrophic thinking about aspects of

bodily functioning.

Third, for most patients with SD, their bodily symptoms—or at least some

of them—may be better explained by a different psychological disorder, such as

depression, an anxiety disorder, or a personality disorder, which makes the addi-

tional diagnosis of SD unnecessary. For instance, gastrointestinal symptoms may

arise from signifi cant anxiety. DSM-IV-TR does not distinguish between an indi-

vidual who has enough physical symptoms to meet Criterion B but no comorbid

psychological disorder and an individual for whom some symptoms are directly

related to a comorbid disorder.

Understanding Somatization Disorder

Like other psychological disorders, somatization disorder can be fully under-

stood only by considering multiple types of factors. These factors include genetics,

bodily preoccupation, symptom amplifi cation and catastrophic thinking, and other

people’s responses to illness. Let’s examine the various factors and how they infl u-

ence one another.

Neurological Factors: Genetics

Most of the progress in understanding the neurological factors that underlie SD has

been in the area of genetics. For example, in a large-scale twin study, researchers found

that genetic effects may account for as much as half of the variability in SD (Kendler

et al., 1995). Note, however, that this fi nding does not imply that the disorder itself

is necessarily inherited; it could be that temperament or other characteristics that are

infl uenced by genetics predispose a person to develop the disorder in certain environ-

ments. (This same point can be made about most fi ndings that link genes to disorders.)

Kendler and colleagues (1995) also reported that characteristics of families have no

consistent effect on whether members of the family develop this disorder. This fi nding

suggests that—in addition to genes—specifi c experiences of an individual, not shared

experiences among members of a family, affect whether a person develops the disorder.

An interesting hint about how genes might affect SD came from a study of

relatives of people with another somatoform disorder, hypochondriasis (a preoc-

cupying belief that the individual has serious illness, despite negative medical tests;

this disorder was mentioned earlier, and will be discussed in more detail shortly).

Researchers found that SD was more frequent in the relatives of people with hypo-

chondriasis, compared to relatives of control participants (Fallon et al., 2000; Noyes

et al., 1997). This fi nding might suggest an underlying genetic link between SD

and hypochondriasis, which is consistent with the fact that both disorders involve

abnormal attention to bodily symptoms.

Psychological Factors: Misinterpretation of Bodily Signals

Like all somatoform disorders, SD involves bodily preoccupation and symp-

tom amplifi cation, as well as catastrophic thinking—in this case, about physical

sensations or fears of illness. These patients may believe, for example, that head-

aches indicate a brain tumor. Their mental processes—particularly attention—focus

on bodily sensations, including the beating of their hearts (Barsky, Cleary, et al.,

1993, 1994), leading to symptom amplifi cation and catastrophic thinking. These

effects also arise in part from faulty beliefs about their bodies and bodily sensations.

For example, people with SD may erroneously believe that health is the absence

ofany uncomfortable physical sensations (Rief & Nanke, 1999). However, most

people without SD experience some somatic symptoms, at least some of the time.

The difference is that people who do not have a somatoform disorder do not habit-

ually develop catastrophic misinterpretations of such sensations. Among a group

of healthy college students, for example, 81% experienced at least one somatic

symptom in a 3-day period (Gick & Thompson, 1997). For people with SD, their

erroneous beliefs about health and illness can increase their level of arousal, which—

because of their increased attention to bodily symptoms—can lead to further bodily

sensations that are then misinterpreted (Mayou & Farmer, 2002).

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