Handbook of Psychology

Definitional, Epidemiological, and Assessment Issues 395

alteration of bowel habit is too strict for the diagnosis„some
surveys have suggested that most investigators use a combi-
nation of abdominal pain and two or more of the Manning
Criteria to diagnose IBS (Camilleri & Choi, 1997).
A revised version of the Rome Criteria, known as Rome II,
has been published (Thompson et al., 1999), making the
criteria less restrictive, and addressing some of the other con-
cerns. No changes in the original pain symptoms were made,
since factor analyses of nonpatients (Taub et al., 1995;
Whitehead et al., 1990) continued to support its inclusion.
However, the second part of the Rome I Criteria was elimi-
nated from the de“nition, and is now considered part of the
nonessential symptoms to be used when attempting to de“ne
subgroups and/or improve diagnostic accuracy (Drossman
et al., 2000). In addition, the requirement of two out of three
pain-related symptoms ensures that altered bowel habit is al-
ways present. The Rome II Criteria, as described in
Drossman et al. (2000) are:
At least 12 weeks or more, which need not be consecutive,
in the preceding 12 months of abdominal discomfort or pain
that has two out of three features:

1.Relieved with defecation,

2.Onset associated with a change in frequency of stool,
and/or

3.Onset associated with a change in form (appearance) of
stool.

Symptoms that cumulatively support the diagnosis of
Irritable Bowel Syndrome include:

Abnormal stool frequency,

Abnormal stool form (lumpy/hard or loose/watery stool),

Abnormal stool passage (straining, urgency, or feeling of

incomplete evacuation),

Passage of mucous, and/or

Bloating or feeling of abdominal distention.

As we can see, the term abdominal discomfortwas added
broadening the symptom description. Abdominal distention
was eliminated from the necessary criteria, and stool consis-
tency was replaced by •formŽ to conform with the Bristol
Stool Scale (O•Donnell, Virjee, & Heaton, 1990).

Epidemiology

The dif“culty in de“ning IBS limits our ability to accurately
determine its prevalence. Currently, however, it is estimated

that its prevalence falls somewhere between 11% and 22%

among American adults (Dancey, Taghavi, & Fox, 1998;

Drossman, Sandler, McKee, & Lovitz, 1982; Talley,

Zinsmeister, VanDyke, & Melton, 1991), depending on

which de“nition is used. These prevalence rates tend to be

fairly consistent around the world (Thompson, 1994), al-

though some surveys suggest that the prevalence of IBS is

lower among Hispanics in Texas (Talley, Zinsmeister, &

Melton, 1995) and Asians in California (Longstreth &

Wolde-Tasadik 1993). The occurrence of IBS in the general

population is substantial, especially if we compares it to the

prevalence rates for other common diseases, such as asthma

(5%), diabetes (3%), heart disease (9%), and hypertension

(11%) in the United States (Wells, Hahn, & Whorwell, 1997).

IBS is the seventh most commonly diagnosed digestive

disease in the United States (Wells et al., 1997), has been

known to account for up to 50% of referrals to gastrointesti-

nal specialists (Sandler, 1990; Wells et al., 1997), and is the

most common diagnosis given by gastroenterologists (Wells

et al., 1997). Women appear to be the most commonly

af”icted„with gender ratios ranging from... , females to

males (1.4 to 2.6:1) (Drossman et al., 1993; Talley et al.,

1995) although, as Sandler points out in his epidemiological

study, such a “nding may be biased toward gender dif fer-

ences in health care utilization. For example, while female

patients seeking help for IBS are overrepresented in Western

countries, they represent only 20% to 30% of the IBS patients

in India and Sri Lanka (Bordie, 1972; Kapoor, Nigam, Ras-

togi, Kumar, & Gupta, 1985).

It is estimated that, in the United States, IBS accounts for

nearly$8 billion a yearin medical costs (Talley et al., 1995),

and that people with IBS are more likely to seek medical

attention for nongastrointestinal complaints, and undergo

surgical procedures (Longstreth & Wolde-Tasadik, 1993).

People with IBS have also been shown to miss up to three

times as many days of work as those without IBS (Drossman

et al. 1993).

Empirical Evidence

There are two important epidemiological studies that best

convey the magnitude of the problem. In 1995, Talley and

colleagues surveyed 4,108 residents of Olmstead County,

Minnesota, between the ages of 20 and 95. They used a pre-

viously validated self-report postal questionnaire (Talley,

Phillips, Melton, Wiltgen, & Zinsmeister, 1989) that identi-

“ed GI symptoms experienced over the past year and deter-

mined the presence of functional GI disorders. Follow-up

reminders were sent at two, four, and seven weeks and a tele-

phone call was made at 10 weeks, which yielded a response