376 Chronic Fatigue Syndrome
disorder occurring since their CFS diagnosis, 66.7% of those
without psychiatric comorbidity had MRI abnormalities ver-
sus only 22.2% with psychiatric comorbidity. The CFS with-
out psychiatric diagnosis group had the highest frequency of
lesions, and these lesions were most often found in the frontal
lobes.
Several investigators have also argued for the presence of
important subgroups of patients including the presence ver-
sus absence of a premorbid psychiatric condition and gradual
versus sudden onset of the illness (DeLuca et al., 1997).
Johnson, DeLuca, and Natelson (1999) also suggest that there
might be two groups of CFS patients, one with sudden onset,
nonpsychiatric, and serious cognitive impairments, and the
other with slow onset, psychiatric comorbidity, and mild cog-
nitive impairment. However, in a community-based sample,
higher frequency of symptoms was not associated with a
greater number of psychiatric diagnoses (Jason, Taylor,
Kennedy, Jordan, et al., 2001), but sudden onset of illness
was associated with psychiatric comorbidity (Jason, Taylor,
Kennedy, Song, et al., 2000). In addition, when patients with
and without a premorbid psychiatric diagnosis were com-
pared, there were no signi“cant differences on sociodemo-
graphic variables, measures of fatigue and symptom severity,
disability, stress, and coping (Jason, Taylor, Kennedy, Song,
et al., 2001). Possible differences between these “ndings and
those of DeLuca and associates (1997) may be attributed to
different ways in which the participants were recruited. In the
Jason, Taylor, Kennedy, Jordan, et al. (2001); Jason, Taylor,
Kennedy, Song, et al. (2000); and Jason, Taylor, Kennedy,
Song, et al. (2001) studies, participants with CFS were re-
cruited using randomized, community-based telephone sam-
pling. In the DeLuca et al. (1997) study, participants with
CFS were self-referred based on media reports about a CFS
treatment center and also recruited by physician referral.
Patients diagnosed with CFS and “bromyalgia have been
found to be substantially more disabled than patients with ei-
ther condition alone (Bombardier & Buchwald, 1996). Jason,
Taylor, Kennedy, Song, et al. (2001) also found that those
with CFS and comorbid FM compared to those with only
CFS had increased symptoms and functional impairment.
Jason, Taylor, and Kennedy (2000) found in a community
sample of individuals with CFS that 15.6% also had FM,
40.6% had multiple chemical sensitivities (MCS), and 3.15%
had FM and MCS, whereas only 40.6% had pure CFS. Future
studies should subclassify patients according to whether they
are pure types or have FM and or MCS.
It is possible that CFS is experienced differently by indi-
viduals depending on the particular illness phase. Fennell
(1995) has proposed a four-phase model for understanding
the phases individuals undergo when coping with CFS: In
Phase 1 of the CFS illness, the individual moves into a crisis
mode after illness onset, wherein he or she experiences the
traumatic aspects of a new illness. In Phase 2, the person
with CFS continues to experience chaos and dissembling,
followed by the eventual stabilization of the individual•s
symptoms. In Phase 3, the person with CFS moves into the
resolution mode, as he or she works to accept the chronicity
and ambiguity of this chronic illness and create meaning out
of the illness experience. Finally, in Phase 4, the person with
CFS achieves integration, wherein he or she is able to inte-
grate the pre- and post-illness self-concepts.
Jason, Fennell, and associates (1999) examined the factor
structure of the Fennell Phase Inventory using a sample of 400
participants, who self-reported that a physician diagnosed
them with CFS on a mail-in questionnaire. A three-factor
solution emerged, yielding a crisis score, a stabilization score,
and an integration score for each individual. A cluster analysis
was then conducted using the three mean factor scores for
each individual, and four clusters emerged. These clusters
matched the four phases predicted by Fennell (Jason,
Fennell, Taylor, Fricano, & Halpert, 2000).
In another study (Jason, Fricano, et al., 2000), 65 patients
diagnosed with CFS by a physician were recruited and ad-
ministered the Fennell Phase Inventory and other measures
assessing CFS-related symptoms, disability, and coping.
Each of the 65 patients was classi“ed as one of four prede-
“ned clusters measuring a crisis phase, a stabilization phase,
a resolution phase, and an integration phase. Results con-
“rmed Fennell•s model, revealing signi“cant dif ferences be-
tween the clusters in terms of levels of disability and modes
of coping. Results suggest that the Fennell Phase Inventory
accurately differentiates phases of adaptation to illness expe-
rienced by individuals with CFS. Phase models might help
researchers better deal with the mass of con”icting re-
search studies in the “eld of CFS. If patients experience these
phases in qualitatively different ways, their responses on
standardized questionnaires could be dramatically different,
depending on the phase of their illness. If a researcher col-
lapses the responses of patients in different phases, the “nd-
ings might be obscured because the patients are experiencing
fundamentally different processes.
Even the construct of fatigue must be better differenti-
ated into various dimensions (e.g., postexercise symptoms,
”are-up symptoms, remission symptoms, aller gy fatigue;
Dechene, Friedberg, MacKenzie, & Fontanetta, 1994). Until
better-differentiated subgroups are developed, it will be ex-
ceedingly dif“cult to identify characteristics common to all
people with the diagnosis of CFS (Friedberg & Jason, 1998).