ORIGINAL ARTICLE Psychology and counselling
Catastrophizing: a predictor
of persistent pain among women
with endometriosis at 1 year
C.E. Martin1,2, E. Johnson1,3,4, M.E. Wechter5, J. Leserman1,6,
and D.A. Zolnoun1,7,*
1Pelvic Pain Research Unit, Division of Advanced Laparoscopy and Pelvic Pain, Department of Obstetrics and Gynecology, University of
North Carolina School of Medicine, Chapel Hill, NC 27599, USA2School of Medicine, Johns Hopkins School of Medicine, Baltimore, MD
21231, USA3Georgia State University School of Nursing, Atlanta, GA 30303, USA4Department of Obstetrics and Gynecology, University of
North Carolina, Chapel Hill, NC 27599, USA5Department of Gynecology, Mayo Clinic Florida, Jacksonville, FL 32224, USA6Department of
Psychiatry, University of North Carolina, Chapel Hill, NC 27599, USA7Department of Obstetrics & Gynecology & Center for Neurosensory
Disorders, University of North Carolina, Chapel Hill, NC 27599, USA
*Correspondence address. email@example.com
Submitted on August 18, 2010; resubmitted on August 2, 2011; accepted on August 9, 2011
background: Endometriosis is the most common gynecological diagnosis among women with chronic pelvic pain, but the underlying
mechanisms of endometriosis-associated chronic pelvic pain remain unclear. Therefore, the objective of this study was to determine the
biopsychosocial predictors of pain improvement among women with endometriosis.
methods: One hundred and fifteen women who presented for treatment of endometriosis-associated chronic pelvic pain at a tertiary
referral center at a university-based hospital participated in this prospective observational study of clinical practice. Participants completed
questionnaires assessing pain, mental health and catastrophizing at entry and 1 year follow-up. The main outcome measure assessed was the
interval change in pain report using the McGill pain 1uestionnaire.
result(s): On average, participants experienced a 37.4% reduction in interval pain (P , 0.001). Adjusted for baseline pain, nulliparity
(P ¼ 0.002) and catastrophizing (P ¼ 0.04) were associated with decreased probability of interval improvement in pain. Those referred for
physical therapy had less interval pain improvement (P ¼ 0.04). However, undergoing hysterectomy was a strong predictor of improvement
in pain (P ¼ 0.008).
conclusion(s): Our study suggests that chronic pain in endometriosis may be more akin to other idiopathic pain disorders. Specifi-
cally, biopsychosocial variables, such as catastrophizing, play an important role in reported severity. Further research on biopsychosocial cor-
relates of chronic pelvic pain in endometriosis is warranted.
Key words: chronic pelvic pain / endometriosis / catastrophizing / pain-related outcomes / psychological factors
Among women with chronic pelvic pain, endometriosis has an esti-
mated prevalence of 33%, making it the most common gynecological
diagnosis in this population (Guo and Wang, 2006). To date, the
classification and treatment of endometriosis has been based on a bio-
molecular conceptualization. However, the underlying mechanisms of
endometriosis-associated chronic pelvic pain remain unclear. In recent
years, there has been a growing interest in the standardized assess-
ment of clinical outcomes in endometriosis. In accordance with the
initiative on methods and measurement and pain assessment in clinical
trials, such an approach will necessitate the objective assessments in
both biomedical and psychosocial domains (Vincent et al., 2010). To
this end, this study examines the biopsychological correlates of pain
report at 1 year in a group of women undergoing treatment for
endometriosis-associated chronic pelvic pain.
Within the larger community of chronic pain patients, there is a
growing recognition that biomedical variables, such as disease severity,
cannot sufficiently explain levels of pain and psychological adjustment
(Vercellini et al., 2007; Taylor and Williams, 2010). We speculate that
persistent pain in endometriosis may be similar to other pain disorders
in that psychosocial variables may play as great of a role as biomedical
factors in pain report. Therefore, the assessment of coping mechan-
isms such as catastrophizing—a well known modifier of chronic pain
treatment outcomes—may shed light on the influence of psychosocial
domains on gynecological pain report and treatment outcomes.
& The Author 2011. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.
For Permissions, please email: firstname.lastname@example.org
Human Reproduction, Vol.26, No.11 pp. 3078–3084, 2011
Advanced Access publication on September 7, 2011doi:10.1093/humrep/der292
Catastrophizing is a term that was originally used by Beck et al.
(1979) to describe a maladaptive coping style used by patients with
anxiety and depressive disorders. More recently, it has been defined
as a negative cognitive and emotional coping response to pain, and
it includes the tendency to amplify and focus on pain symptoms as
well as feelings of helplessness and pessimism (Sullivan et al., 2001).
Catastrophizing has emerged as an important determinant of short-
and long-term pain-related outcomes and consistently been associated
with higher pain levels. This relationship holds true in a variety of
conditions such as neuropathic pain, low back pain and scleroderma
(Buer and Linton, 2002; Turner et al., 2002; Sullivan et al., 2005;
Edwards et al., 2006a,b; Hanley et al., 2008). Across both non-patient
and chronic pain populations, it has been shown that individuals
reporting high levels of catastrophizing demonstrate increased muscu-
loskeletal tenderness and heightened pain sensitivity; they also appear
to be at a higher risk for the development of post-surgical and persist-
ent pain syndromes (Severeijns et al., 2001, 2004; Granot and Ferber,
2005; Turner et al., 2005).
The exact mechanism through which catastrophizing is related to
pain is not entirely understood. It has been postulated that the
emotional and cognitive changes that characterize catastrophizing
may disrupt descending endogenous pain-inhibitory pathways (Sullivan
et al., 2001). Furthermore, catastrophizing is shown to be associated
with enhanced activity in the pain-processing regions of the brain
(Gracely et al., 2004; Seminowicz and Davis, 2006; Lloyd et al.,
2008). Most notably, however, since endometriosis is an inflammatory
process, findings of a positive association between catastrophizing and
inflammatory cytokines in conditions such as rheumatoid arthritis may
be relevant to the study of pain in endometriosis (Evers et al., 2003;
Yin et al., 2005; Edwards et al., 2008).
In this study, we hypothesized that among women with endome-
triosis, those with higher levels of catastrophizing would experience
greater pain at baseline and at 1-year. Specifically, we sought to inves-
tigate the effect of the following variables on pain report at baseline
and 1-year follow up: demographic factors (e.g. age, education,
parity), clinical histories (e.g. pain duration, prior treatments), interval
treatments (e.g. medical, surgical) and psychosocial factors (e.g.
mental health, catastrophizing). For validation purposes, we also inves-
tigated whether or not we were able to replicate the findings of others
with respect to the beneficial effects of hysterectomy in our cohort
Materials and Methods
Sample and procedure
A total of 115 women with endometriosis were consecutively recruited
from a tertiary referral pelvic pain clinic between April 2003 and Septem-
ber 2006. The Institutional Review Board of the University of North
Carolina (UNC) approved the study. All English-speaking and literate
women between the ages of 18 and 65 who were new referrals for evalu-
ation of endometriosis-associated chronic pelvic pain at the UNC pelvic
pain clinic were eligible for participation. We did not exclude anyone
based on pre-existing psychological and/or physical condition. These
patients were part of a larger, previously published study on psychosocial
correlates of chronic pelvic pain (Meltzer-Brody et al., 2007). From the
larger study (n ¼ 628 enrolled of 722 eligible), 459 were new referrals
to the clinic and were asked to be in a longitudinal study. Of those, 310
agreed to participate and returned at least one follow-up questionnaire
(67.5% return rate). For the current paper, we studied only those new
longitudinal patients with endometriosis-associated chronic pelvic pain
(n ¼ 123). We excluded eight patients for whom we could not identify
medical record data; thus, our cohort consists of 115 participants. Later,
wedescribe in detailour methodology
endometriosis-associated chronic pelvic pain case status.
Following informed consent and prior to examination, participants com-
pleted a battery of questionnaires assessing severity of pain, quality of life
and psychosocial variables such as catastrophizing. In addition, participants
completed a baseline demographic and medical history questionnaire
before undergoing standard evaluation by the clinical team. The examining
physicians, regionally recognized as experts in the field of pelvic pain, did
not review participants’ questionnaire responses. Their findings, diagnostic
impressions and recommended treatments [e.g. medications, surgery,
referral to physical therapy (PT)] at baseline and over the follow-up year
were recorded in electronic medical records. A team of four trained
research associates then abstracted these data.
We used two complimentary methods for ascertaining case status as
endometriosis- associated pelvic pain: (i) patient self-report on entry per
demographic questionnaire and (ii) review of electronic medical records.
Based on our record review, we could confirm a surgically based diagnosis
of endometriosis for 111 patients; four women were surgically diagnosed
during the study period. Therefore, our cohort consists of 115 women
who were surgically diagnosed with endometriosis and experienced
intractable pelvic pain despite conventional treatment modalities; 93%
completed the 1 year pain questionnaire.
Demographic and clinical history
The baseline study entry questionnaire provided demographic and medical
history information concerning age, years of education, race, marital status,
duration of pelvic pain, number of prior surgeries for pelvic pain and pre-
vious hysterectomy. Number of prior surgeries for pelvic pain was trun-
cated to six surgeries in order to reduce outliers. As a result of our
population demographics, the race and marital status variables were
treated as bivariates in data analyses (e.g. Caucasian versus other,
married versus not married). When self-reported data were missing for
the duration of pelvic pain and previous hysterectomy variables, infor-
mation on these variables was obtained from the medical records.
Medical records were abstracted for additional demographic and clinical
variables (e.g. parity, co-morbid pain disorder) as well as treatments (e.g.
surgical versus medical) utilized over the study period. For secondary ana-
lyses, we examined those having the most common type of surgery (e.g.
hysterectomy) versus other types of pelvic surgery (e.g. oophorectomy,
lysis of adhesions). We also abstracted information about the three
common types of medical treatments used before the study and during
the follow-up year: (i) PT, (ii) hormonal therapies (e.g. oral contraceptive
pills, leuprolide, levonorgestrel-releasing intrauterine system) and (iii)
central nervous system medications (e.g. antidepressants, anticonvulsants,
sleep aids, muscle relaxants). Patients were considered to have another
co-morbid pain disorder if any of the following were noted in the elec-
tronic medical records from the initial visit: chronic headaches (migraines),
irritable bowel syndrome, interstitial cystitis, fibromyalgia, chronic fatigue
syndrome, temporomandibular disorder or chronic lower back pain.
To determine the severity of pelvic pain at baseline and follow-up, the
short form McGill pain questionnaire (SF-MPQ) was used (Melzack,
1987). The SF-MPQ has two components, the present pain intensity
(PPI) and pain rating index (PRI). The PPI component of the questionnaire
Catastrophizing and chronic endometriotic pain
consists of a visual analog scale and is conventionally used to assess the
present pain levels. Consistent with conventional practice, we used the
PRI component (McGill total pelvic pain score) in this study since it pro-
vides a global multi-dimensional pain severity rating over time. The
McGill total pelvic pain score (PRI component) is composed of 15
groups of qualitative descriptors (11 sensory and 4 affective) that are
rated on an intensity scale (0 ¼ none, 1 ¼ mild, 2 ¼ moderate and 3 ¼
severe). Participants were asked to rate the descriptors of the pelvic
pain they had experienced in the previous 2 weeks. The McGill total
pain score was calculated from the sum of the 15 items, with a range of
0–45. The SF-MPQ is highly correlated with the longer version of the
MPQ (Katz et al., 1999). It has demonstrated a high test-rest reliability
of 0.96 (Grafton et al., 2005) and a high internal consistency with a Cron-
bach’s a of 0.86 (Mason et al., 2008). Cronbach’s a was 0.90 at baseline in
the current study.
To assess mental health, we used the mental health subscale (norm-based
scoring) of the short form 12 Health Survey (SF-12) where a high score
indicates better mental health. The SF-12 has a high internal consistency
and reproducibility with a Cronbach’s a of 0.87 (Ware et al., 2002). It
has been shown to be able to discriminate between types and severity
of disease between patients with medical disorders alone as well as
those with both medical and psychological disorders (McHorney et al.,
1993, 1994). The mental health subscale has strong predictive properties
for health outcomes with a test-retest reliability of 0.76 (Ware et al.,
1996). SF-12 Cronbach’s a was 0.89 at baseline in the current study.
To measure catastrophizing of pain, we used the catastrophizing subscale
of the Coping Strategies Questionnaire: CSQ (Rosenstiel and Keefe,
1983). The CSQ was designed to evaluate cognitive and behavioral
coping strategies in chronic pain syndromes. The catastrophizing scale
ranges from 0 to 6, with a high score indicating higher catastrophizing
(e.g. ‘I feel I can’t stand it anymore’; ‘It is terrible and I feel it’s never
going to get any better’). This scale has been shown to predict poor
health in other clinical samples, such as Irritable Bowel Syndrome patients
(Drossman et al., 2000). Data analyses were performed with the continu-
ous measure; however, in the text, we report the following groups based
on their catastrophizing score (range 0–6): mild (1–2), moderate (3–4)
and severe (5–6). The catastrophizing subscale of the CSQ has extensively
been utilized in the literature. It has high internal consistency and reliability
with a Cronbach’s a of 0.78 (Rosenstiel and Keefe, 1983). This scale has
been found to have strong predictive properties for health outcomes
among patients with painful conditions (Robinson et al., 1997; Schanberg
et al., 1997) witha test-retest reliability varying from 0.80 to 0.91
(Rosenstiel and Keefe, 1983). Cronbach’s a was 0.73 at baseline in the
Statistical analyses were performed using SAS 9.1. Descriptive statistics
(mean and standard deviation for continuous variables; frequency and per-
centages for bivariate variables) for demographics, pain report and psycho-
logical variables are reported for the entire cohort in the ‘Descriptive
Analyses’ section of the results below. We examined the distributions
of the pain variables at baseline and at 12 months to ensure approximate
normality. Continuous variables (e.g. catastrophizing) were analyzed as
continuous variables but were grouped into categories of mild, moderate
and severe for presentation and clarity purposes only. Paired Student’s
t-tests were used to compare changes in pain over time for the group
as a whole.
In order to determine predictors for pain severity at baseline and at 12
months, we ran multiple regression analyses allowing variables with P ,
0.10 or those with clinical interest to stay in the models (Table I). For
regression analyses of baseline pain (McGill total pelvic pain), we tested
the significance of the following predictor variables: (i) demographic
factors (age, education, race, marital status, parity), (ii) previous medical
history (duration of pelvic pain, number of surgeries for pelvic pain,
PT for pain) and (iii) baseline mental health (catastrophizing, SF-12
For regression analyses of McGill total pelvic pain at 1 year, we first
entered baseline pain into the regression models in order to assess the
change in pain over time. We then investigated the joint and independent
contributions of baseline variables and treatments used during the 1-year
Predictor variablesLS mean
≤30 (n ¼ 38; 33%)
31–39 (n ¼ 40; 35%)
≥40 (n ¼ 36; 32%)b
Years of education
High school diploma or less
(n ¼ 34; 30%)
Some college (n ¼ 32; 28%)
College degree or more
(n ¼ 48; 42%)c
# Prior pelvic surgeries
None (n ¼ 23; 20%)
1–2 (n ¼ 59; 52%)
≥3 (n ¼ 32; 28%)d
Past PT treatment
Yes (n ¼ 9; 8%)
No (n ¼ 105; 92%)
Mild (n ¼ 64; 56%)
Moderate (n ¼ 37; 33%)
Severe (n ¼ 13; 11%)e
Table I Factors associated with baseline pain severitya.
Baseline McGill total pelvic pain (n 5 114)
LS, least squared; SE, standard error; b, standardized beta coefficient showing the
following: (i) the direction of the relationship and (ii) the amount in standard
deviation units that the pain score changed for each unit of the predictor variable.
aTable shows the results of stepwise multiple regression analyses of pain at baseline
predicted by demographic, clinical and psychological variables. Only those variables
with P , 0.10 are in the final models. P values are based on the non-grouped
variables. General linear models controlling for all variables were used to obtain
least-squared means and standard errors. Continuous variables (age, years of
education, # prior pelvic surgeries, catastrophizing) were grouped for the purposes
of presentation and comparison.
bThose who were ≥40 years old had less pain at baseline than those aged younger
than 30 years (P ¼ 0.02).
cThose who had at least a college degree had less pain at baseline than those with
some college (P , 0.001) or no more than a high school diploma (P ¼ 0.004).
dThose who had undergone ≥3 past pelvic surgeries had more pain at baseline than
those who had undergone 1–2 past pelvic surgeries (P ¼ 0.01).
eThose who had severe catastrophizing had more pain at baseline than those with
mild catastrophizing (P , 0.001).
Martin et al.
follow-up period. Thus, the following variables were included in the pre-
dictive models of total pelvic pain at 1 year: (i) baseline McGill total
pelvic pain score, (ii) baseline mental health (catastrophizing, SF-12
mental health), (iii) demographic factors (age, race, marital status, edu-
cation) and (iv) interim treatments (surgery, PT, medications) (Table II).
These regression models were run with the continuous form of predictor
variables (e.g. catastrophizing, education, age, number of prior pelvic sur-
geries). For presentation purposes though, we also ran post hoc general
linear models with least-squared means (Student’s t-tests) for categorical
predictors in order to determine which categories of patients (e.g.
severe catastrophizing, less than college degree) had more pain. To
reduce the number of variables (maximum of nine in all our analysis),
we first tested demographic and medical history variables and only
included the significant ones in the final model. In addition, due to
co-linearity, mental health variables (SF-12 and catastrophizing) were run
Our cohort primarily consisted of Caucasian (85%), married women
(67%), aged 19–45 (85%) with at least some college education (70%);
46% were parous. With a mean duration of 5.6 (+5.3) years of pelvic
pain, the majority of our subjects had underwent two previous surgeries
(mean 1.9+1.7) for treatment of pelvic pain; 34% (n ¼ 39) had a pre-
vious hysterectomy at entry into the study. Slightly over half of our partici-
pants (n ¼ 64; 55.6%) had been diagnosed with at least one other
co-morbid pain condition (e.g. fibromyalgia, migraine headache).
Compared with women in the US population, women in our study were
considerably below average (approximate 25th percentile) in their mental
health status, with a mean SF-12 score of 42.8+10.3 (Ware et al., 2002).
Overall, 43.47% of participants scored moderate to severe on catastro-
phizing (Fig. 1). Most experienced moderate levels of pain (mean McGill
pain score 19.45+10.0), with scores higher than those reported for
fibromyalgia (15+6.7) patients (Geisser et al., 2003).
Most demographic, clinical and psychosocial characteristics did not differ
between patients undergoing medical therapy or medical in conjunction
with surgical therapy. However, on average, the non-surgical group
entered the study having a longer duration of pelvic pain by 2.4 years
(P ¼ 0.01), one additional past surgery for pelvic pain (P ¼ 0.05) and a
greater likelihood of having a previous hysterectomy (P ¼ 0.008).
Most patients improved in their pain scores from entry to follow-up
(74.8%). Patients reported an average of a 37.4% decrease in pain (P ,
0.001) during the year. Both surgical and non-surgical patients improved
significantly over time (P , 0.001), with a trend for those having surgery
to have a greater mean pain improvement (50.3%) compared with
those without surgery (31.2%; P ¼ 0.05). The most common medical
treatments included hormonal therapies (59.1%) and central nervous
system medications (34.8%). The most common surgeries performed
over the year included hysterectomy (11.3%), oophorectomy (11.3%)
and lysis of adhesions (10.4%). In further analysis, we found that the
trend for improved 1-year pain outcomes among those undergoing
surgery was attributable to interval hysterectomy. Thus, in later analyses,
we focused on hysterectomy rather than all surgeries.
Baseline pain analyses
We first analyzed the demographic, previous medical history and mental
health correlates of baseline total pelvic pain. Greater pain at study
entry was associated with younger age (P ¼ 0.02), less education (P ¼
0.01), more previous pelvic surgeries (P ¼ 0.05), past PT treatment
(P ¼ 0.03) and coping with pain by catastrophizing (P , 0.001). Specifi-
cally, further analysis showed that those 30 years or younger, those
having less than a college degree, those having three or more pelvic sur-
geries and those who cope via severe catastrophizing had the worst
pain at baseline. These predictors accounted for ?35% of the variance
in baseline pain scores. Catastrophizing alone in these models explained
21% of the variance in pain scores, with those coping by severe catastro-
phizing having about a 9-point higher pain score (range 0–45) than those
who cope by mild catastrophizing. Since the mental health (SF-12) and cat-
astrophizing measures were highly correlated (r ¼ 20.53; P , 0.001),
they could not be in the statistical model simultaneously due to
co-linearity. Good mental health (i.e. high SF-12 mental health score)
was also associated with less pain at baseline when catastrophizing was
not included in the model (b ¼ 20.25; P , 0.001).
Baseline McGill pain
Years of education
High school diploma or less
(n ¼ 31; 29%)
Some college (n ¼ 29; 27%)
College degree or more
(n ¼ 46; 44%)b
0 (n ¼ 55; 52%)
≥1 (n ¼ 51; 48%)
Yes (n ¼ 13; 12%)
No (n ¼ 93; 88%)
Other pelvic surgery
Yes (n ¼ 22; 21%)
No (n ¼ 84; 79%)
Yes (n ¼ 49; 46%)
No (n ¼ 57; 54%)
Mild (n ¼ 61; 58%)
Moderate (n ¼ 33; 32%)
Severe (n ¼ 12; 11%)c
Table II Predictors of pain severity at 1 year follow-upa.
12 months McGill pelvic pain (n 5 106)
LS, least squared; SE, standard error; b, standardized beta coefficient showing the
following: (i) the direction of the relationship and (ii) the amount in standard
deviation units that the pain variable changed for each unit of the predictor variable.
aTable shows results of stepwise multiple regression of pain at 1 year predicted by
demographic, baseline pain, interval treatment and psychological variables. Only
those variables with P , 0.10 orof interestarein the final models. P values arebased
on the non-grouped variables. General linear models controlling for all variables
were used to obtain least-squared means and standard errors. Continuous variables
(years of education, catastrophizing) were grouped for the purpose of presentation
bThose who had at least a college degree tended to have less pain at 1 year than
those with a high school diploma or less (P ¼ 0.06), controlling for baseline pain.
cThose with severe catastrophizing had more pain at 1 year than those with
moderate catastrophizing (P ¼ 0.03) and those with mild catastrophizing (P ¼ 0.03),
controlling for baseline pain.
Catastrophizing and chronic endometriotic pain
Pain at 1 year
Controlling for baseline pain, we examined the demographic, medical
history, mental health and interval treatments predicting pelvic pain at 1
year (Table II). Those who had higher pain scores at 1 year after control-
ling for entry pain were nulliparous (P ¼ 0.002), less likely to have a hys-
terectomy during the follow-up period (P ¼ 0.008), more likely to
receive PT during the follow-up (P ¼ 0.04), slightly more likely to be
less educated (P ¼ 0.07) and more likely to cope via catastrophizing at
study entry (P ¼ 0.04). Having a hysterectomy explained ?8% of the var-
iance in pain at 1 year, after controlling for baseline pain. Of the 13 people
who had a hysterectomy during follow-up, only one reported follow-up
pain above the median pain score for the entire cohort, compared with
59% of those who did not have this surgery.
The predictors of pain at 1 year did not change when we excluded those
subjects who entered the study with a previous hysterectomy. Specifically,
the standardized parameter estimate and significance (b ¼ 20.287; P ¼
0.01) for the effect of interim hysterectomy were still notable when those
with a prior hysterectomy were excluded from the analyses, compared
with the results for the entire cohort shown in Table II.
Catastrophizing wasasignificantpredictorof painat1year,explaining3%
of the variance in pain outcomes. At baseline, however, catastrophizing
accountedfor 21% of the variance in pain levels. This seemingly unexpected
observationis attributable to theinclusion of baselinepain in the1 yearstat-
istical model. Since baseline pain explained a large portion of the variance
(41%) in 1 year pain outcomes, not much variance was left to be accounted
for by catastrophizing despite its significant association with 1 year pain
levels. Changes in pain scores within and between catastrophizing groups
(mild, moderate, severe) are shown in Fig. 1. Although all groups tended
to decreasein their pain scores, thosewho exhibited severecatastrophizing
at baseline started and ended the study with higher pain levels. Only those
with mild (P , 0.001) and moderate (P , 0.001) levels of catastrophizing
showed significant pain improvement at 1 year.
Our data suggest that biopsychosocial factors, specifically catastrophiz-
ing, may play a pivotal role in pain experience among women with
endometriosis-associated intractable pain. In our cohort, pain severity
at entry and at 1 year was more related to catastrophizing than demo-
graphic and conventional clinical variables. This effect is more pro-
nounced when evaluating group differences, with women who
demonstrated severe catastrophizing at baseline having a mean pain
score 1.5 standard deviation units higher (effect size d) than those
demonstrating mild catastrophizing, indicating a large effect size.
The exact mechanism by which catastrophizing influences baseline
pain report and its interval improvement—or lack thereof—is not
endometriosis-associated pelvic pain may be more complex in some
patients in that pre-existing biopsychosocial factors may play a key
role in pain-related outcomes.
Within the pain literature, there continues to be a debate over
whether catastrophizing is a cause or a result of chronic pain. To
date, there are no longitudinal studies that examine whether catastro-
phizing is modified by a persistent pain state. There is, however, evi-
dence that in both healthy adults and in those with chronic pain,
catastrophizing remains stable over weeks and months, and it may
not change even after the resolution of acute pain (Keefe et al.,
1989; Sullivan et al., 1995; Edwards et al., 2004).
Consistent with findings of other investigators, we found that nulli-
parity (Bulletti et al., 2010), lower levels of education (Dmowski et al.,
1997) and younger age (MacDonald et al., 1999) were associated with
higher pain report. Specifically, younger women with lower education
were more likely to experience higher pain levels at 1 year following
initiation of therapy in our clinics. Nevertheless, the majority of the
subjects (74.8%) reported an average of 37.4% reduction in pain at
1 year. Since treatment modalities are guided by clinical judgment
and a host of individualized variables, we cannot comment about
any specific treatment (surgical versus medical)-related outcomes.
However, we can assert that the variables associated with assignment
to therapy were consistent with conventional clinical practice. For
example, women with previous hysterectomy (P ¼ 0.008), longer dur-
ation of pain (likely to be a proxy for previously failed surgical interven-
tion; P ¼ 0.01) and multiple past surgeries for pelvic pain (P ¼ 0.05)
were more likely to be managed medically.
We also found that surgical history was related to pain severity and
improvement (Leserman et al., 2006). Specifically, women entering the
study with three or more past pelvic surgeries had more pain at base-
line than those entering with fewer surgeries. This may be due to mul-
tiple surgeries being an indicator of intractable pain that does not
improve with treatment. Our study additionally confirms the findings
pilot studysuggests that
Figure 1 Differences between baseline and 1-year McGill total pelvic pain within catastrophizing groups (P-values are from paired Student’s t-tests
between baseline and 1-year McGill total pelvic pain scores within each catastrophizing group).
Martin et al.
of others concerning the beneficial effect of hysterectomy (Carlson
et al., 1994; Farquhar et al., 2006), while other types of surgery
(e.g. oophorectomy) and medical treatments comparatively were
not as effective. In fact, those who had prior PT and/or were referred
to PT in the intervening year had more pain at both baseline and
follow-up. The association between referral to PT and poorer pain
outcomes, which is likely to be a surrogate marker for pelvic
floor muscle pain, is consistent with our ‘clinical observation’ in
that women with severe pelvic pain often have co-morbid pelvic
floor muscle pain and a poor quality of life. This in turn prompts
the clinician to make a referral to PT for further evaluation and
There are potential limitations that are important in the interpret-
ation of our findings. First, the diagnosis of endometriosis was based
on medical records and patient self-report. While all participants
had undergone surgical evaluation with subsequent diagnosis of
endometriosis-associated intractable pain, we did not have medical
record data on histological findings at the time of surgery. Second,
due to small sample size, we were unable to investigate the joint
and independent contributions of other known psychosocial variables
(e.g. histories of trauma and abuse) on interim pain report. Lastly, we
were unable to compare the merits of specific treatment modalities in
symptom improvement. Treatment allocation was reflective of phys-
icians’ practice pattern and patient preference. Since treatment assign-
ment was based on the doctor patient interaction, it is reasonable to
assume the ‘best case scenario’, in that the selected course of therapy
had the greatest odds of success in a given patient (Joyce and Piper,
1998; Horne, 1999). Nonetheless, the magnitude of improvement in
pain in this study is analogous to that of other chronic pain conditions
(Spiegel et al., 2009).
Our data suggest that endometriosis is a complex condition in
which the traditional one-dimensional focus on end-organ gynecologi-
cal factors may not be sufficient in advancing our understanding of the
optimal treatment of this condition. In our cohort, psychological
factors had a significant influence on pain report. Larger studies are
urgently needed to parse out the contributions of the neurobiological
and psychosocial domains in the genesis and treatment of
persistent pain states in women with endometriosis (Edwards et al.,
2006a,b, 2009).Untilthen, future
into account the role of psychological factors in pain-related
investigations should take
In the spirit of horizontal collaboration, each author contributed
equally to (i) drafting the article or revising it critically for important
intellectual content as well as (ii) final approval of the version to be
published in addition to (iii) individual contributions to the conception
and design, or acquisition of data, or analysis and interpretation of data
as follows: C.E.M. was involved in data acquisition, analysis, interpret-
ation of data; E.J. played a role in data acquisition, interpretation, con-
ceptualization/design and analysis;
conceptualization/design, interpretation of data; J.L. took part in
analysis, conceptualization/design, acquisition and interpretation of
data; D.Z. played a role in conceptualization, data acquisition and
interpretation, as well as analysis.
The authors thank the Hannah family for their charitable donations
which were the seed grant for the inception of the Pelvic Pain
Research Unit and its subsequent collaborative work at UNC.
This research was funded in part by a Summer Undergraduate
Research Fellowship and the Department of Obstetrics and Gynecol-
ogy at the University of North Carolina at Chapel Hill, National Insti-
tute of Heath awards K23 HD 053631 and UL1RR025747 from the
National Center for Research Resources.
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