294 Pain Management
episode. Thus, in both recurrent acute pain and chronic pain
the symptom may appear to serve no useful purpose.
Chronic painpersists and can last for months, years, and
even decades beyond any period for which healing of the initial
injury is expected. There have been some suggestions
regarding plasticity within the nervous system where pro-
longed pain leads to neurophysiological changes and increased
sensitization within the central nervous system (CNS) that per-
petuate the experience of pain even when the initial cause has
resolved (Coderre, Katz, Vaccarino, & Melzack 1993). The av-
erage duration of pain noted for patients treated at specialized
clinics typically exceeds seven years (Flor, Fydrich, & Turk,
1992).
As is the case in recurrent acute pain, in chronic pain
syndromes (e.g., spinal stenosis, osteoarthritis), the pain does
not appear to have any obvious useful function. Pain that is
chronic or recurrent can signi“cantly compromise quality of
life and, if unremitting, may actually produce physical harm
by suppressing the body•s immune system. Because of sig-
ni“cant psychological contributions, we focus on chronic
pain in this chapter.
UNIDIMENSIONAL CONCEPTUALIZATIONS
OF CHRONIC PAIN
We contrast two types of models or conceptualizations of
pain:unidimensionalones that focus on single causes of the
symptoms reported and multidimensionalones that empha-
size the contributions of a range of factors that in”uence
patients• experiences and reports of pain.
Biomedical Model of Chronic Pain
The traditional biomedical view of pain is reductionistic. It as-
sumes that reports of pain must be associated, in a proportion-
ate manner, with a speci“c physical cause. As a consequence,
the extent of pain should be directly related to the amount of
detectable neurophysiological perturbations. Health care
providers often undertake Herculean efforts (at great expense)
attempting to establish the speci“c link between tissue dam-
age and the severity of pain. The expectation is that oncethe
physical cause has been identi“ed, appropriate treatment will
follow. Treatment will then focus on eliminating the putative
cause(s) of the pain or chemically (e.g., oral medication, re-
gional anesthesia, implantable drug delivery systems), surgi-
cally (e.g., laminectomy), or electrically (e.g., spinal cord
stimulation) blocking the pain pathways.
There are several perplexing features of chronic pain that
do not “t neatly within the traditional biomedical model, with
its suggestion of an isomorphic relationship between pathol-
ogy and symptoms. For example, pain may be reported even
in the absence of an identi“ed pathological process. It is esti-
mated that one-third to one-half of all visits to primary care
physicians are prompted by symptoms for which no biomed-
ical causes can be detected (Kroenke & Mangelsdorff, 1989).
In 80% to 85% of the cases, the cause of back pain is un-
known (Deyo, 1986). The postulated neural plasticity„
central sensitization explanation for these “ndings„has only
been support in acute, animal pain models and has yet to be
con“rmed for chronic pain.
Conversely, imaging studies using computed tomography
(CT) scans and magnetic resonance imaging (MRIs) have
noted the presence of signi“cant pathology in up to 35% of
asymptomatic people (e.g., M. Jensen, Brant-Zawadzki,
Obuchowski, Modic, & Malkasian Ross, 1994; Wiesel,
Tsourmas, Feffer, Citrin, & Patronas, 1984). Similarly,
asymptomatic individuals may have signi“cant degrees of
degeneration, and more importantly, a similar prevalence
of disk herniation that is comparable to symptomatic people
with back pain (Boos et al., 1995). Yet, they do not appear to
experience any pain. Thus, those who report severe pain with
noidenti“able pathology, and those with demonstrable pa-
thology may notreport pain.
Not all people experiencing pain seek medical care. There
are large numbers of people with recurrent and chronic pain
problems who do not seek medical attention. For example,
Brattberg, Thorslund, and Wikman (1989) observed that
up to 40% of the adult population sampled reported consid-
erable pain lasting longer than six months, yet the majority
did not seek any medical care. Similarly, in a survey of
nurses, Linton and Buer (1995) found that the majority re-
ported moderate to severe pain oftenoralwaysbut they indi-
cated that they had not missed a single day of work due to
pain.Psychogenic Model of Chronic PainAs is frequently the case in medicine, when physical expla-
nations seem inadequate or when the results of treatment are
inconsistent, psychological alternatives are proposed as
causal explanations. Moreover, if the report of pain is recal-
citrant to appropriatetreatment that should eliminate or alle-
viate the pain, it is assumed that psychological processes are
involved. The Psychogenic view is the opposite side of the
coin of the biomedical model. If the pain reported is deemed
to be disproportionate„based on the subjective opinion of
the health care provider„to any objectively determined
pathological process, it may be attributed to psychological
causes and thus are psychogenic.