Menstrual cycle influences on pain and emotion in women with fibromyalgia

Journal of Psychosomatic Research 57 (2004) 451 – 458

Menstrual cycle influences on pain and emotion in women with fibromyalgia Carmen Alonso*, Barbara L. Loevinger, Daniel Muller, Christopher L. Coe Department of Psychology, University of Wisconsin, 1202 West Johnson Street, Madison, WI 53706-1696, United States Received 30 September 2003; accepted 12 May 2004

Abstract Objective: This study examined the influence of the menstrual cycle on pain and emotion in women with fibromyalgia (FM) as compared with women with rheumatoid arthritis (RA) and to healthy controls. Methods: One hundred and twenty-five premenopausal women (21-45 years old) participated in this study (57 with FM, 20 with RA, and 48 controls). Pain and emotion assessments were conducted during the follicular and the luteal phases of the menstrual cycle. Results: Women with FM experienced more pain,

menstrual symptoms, and negative affect than did women with RA and the controls. All women reported less positive affect during the luteal phase, although this pattern was more pronounced in women with FM and RA than in controls. Conclusion: Although FM pain did not vary across the menstrual cycle, these results point to the importance of considering the lower level and cyclical nature of positive affect when studying women with chronic pain. D 2004 Elsevier Inc. All rights reserved.

Keywords: Emotion; Fibromyalgia; Menstrual cycle; Pain; Rheumatoid arthritis

Introduction The significance of the menstrual cycle in women’s physical and psychological well-being remains controversial. With regard to pain and discomfort, it is typically assumed that pain sensitivity varies across the menstrual cycle and is higher in the luteal phase. This assumption has been verified in studies that found a lower pain threshold in response to experimentally induced pain, such as ischemic pain or cold pressor tasks, during the luteal phase [1,2]. However, Tedford et al. [3] obtained results in the opposite direction, with reduced pain sensitivity during the luteal phase. Hapidou and Rollman [4] further challenged the notion of greater pain sensitivity during the luteal phase when they found that pain sensitivity, identified by tender point palpation, was greater in the follicular phase in normally cycling women. In addition, Johns and Littlejohn [5] reported that pain sensitivity, measured using a dolorimeter at 18 tender and 4 control points, did not correlate with the menstrual phase.

* Corresponding author. Tel.: +1 608 262 5346; fax: +1 608 262 4029. E-mail address: [email protected] (C. Alonso). 0022-3999/04/$ – see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2004.05.003

The relationship between the menstrual cycle and pain sensitivity is of particular relevance to women who experience chronic pain, such as in the case of fibromyalgia (FM). FM is a pain disorder of unknown etiology found in an estimated 3–6 million Americans, including children and the elderly [6]. As many as 90% of the patients are women [7]. The FM diagnosis requires (1) widespread pain affecting the musculoskeletal system and (2) tenderness in at least 11 of 18 defined points [8–10]. In clinical settings, the manifestation of pain and tenderness is often combined with other characteristic symptoms, including nonrestorative sleep, fatigue, stiffness, headache, irritable bowl syndrome, and mood disorders [9]. Women with FM are thought to experience more FM pain during the luteal phase, and perimenstrually, as compared with healthy control women [7,11]. More generally, a premenstrual worsening of FM symptoms has also been reported in the literature [12]. However, Macfarlane et al. [13] conducted a large epidemiological study involving 1178 women, of which 11.2%, or 132 women, experienced widespread pain, and concluded that hormonal factors were not associated with pain symptoms. This lack of consensus led us to reevaluate the influence of the menstrual cycle and to consider whether the women’s presentation and emotional state might influence the effect of the menstrual cycle on pain sensitivity.

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Menstrual influences have also been extensively investigated with regard to emotion. Increased negative affect and decreased levels of self-reported well-being have been documented during the luteal phase (e.g., Ref. [14]). Similarly, women with FM have been shown to experience more psychological distress and less positive affect than do healthy controls during the luteal phase [7,11,15]. Although both pain and affect have been related to the menstrual cycle, the specific relationship between those two factors remains unclear. For instance, Herrera et al. [16] found that among forty 19- to 24-year-old women, depressive subjects reported more pain across the menstrual cycle than the nondepressive subjects did. On the other hand, Laessle et al. [17] found that although somatic complaints, such as abdominal pain and breast tenderness, were significantly related to the phases of the menstrual cycle in 30 healthy young women, the cycle-related hormone fluctuations could not be directly linked to marked changes in affect. Therefore, it seemed critical to combine a study of objective pain measures, including tender point and dolorimetry assessments, with an evaluation of positive and negative affect. In addition to examining the influence that the menstrual cycle has on pain and emotion in women with FM, we compared their responses to women with another chronic pain condition, rheumatoid arthritis (RA). RA has a more established etiology as an autoimmune disorder and is not as likely as FM to be associated with depression and other types of psychological disturbance [18,19]. The primary hypotheses of the study were that (1) women with FM would experience increased pain sensitivity and a worsening of symptoms during the luteal phase, and (2) FM women would manifest more negative and less positive affect than will the women with RA and the healthy controls, especially during the luteal phase of the menstrual cycle.

Method Participants A total of 132 premenopausal women (21– 45 years of age, 92% Caucasian), with regular menstrual cycles, participated in this study: 64 with FM, 20 with RA, and 48 healthy controls. Potential participants were recruited from local rheumatology and pain clinics and from advertisements in a local newspaper and in a local women’s magazine. To be eligible for the study, FM patients had to have been diagnosed by a rheumatologist or primary care physician and had to meet the American College of Rheumatology (ACR) 1990 diagnostic criteria for FM [20]. Seven participants who stated that they had an FM diagnosis but did not meet the 11 positive tender points criterion were omitted from the analyses. The RA patients also had been diagnosed by a rheumatologist and were screened for rheumatoid factor and antinuclear antibody. Healthy control participants were excluded if they reported

any chronic physical illness. Participants were excluded from the study if they had been diagnosed with both conditions, FM and RA, if they had been taking cortisone during the previous 3 months, and if they were taking any narcotic medication. In addition, any other physical illness that could cause pain, such as systemic lupus, diabetes, polycystic ovarian syndrome, or thyroid disease, was considered as an exclusion criterion. The three groups of participants were not significantly different regarding age, education level, employment status, income, partner status, or number of children (see Table 1). Procedure Potential participants were screened via phone interview and were invited to come for a first consent meeting if they met the study criteria. During the first meeting, written consent was obtained, as approved by the Institutional Review Board, and menstrual cycle symptoms were assessed. After the initial meeting, pain and psychosocial evaluations were conducted on two occasions: during the follicular and the luteal phases of the menstrual cycle. The date of the luteal visit was scheduled during the week prior to next menses and the date of the follicular visit during the week after menstruation. The order of the two visits was counterbalanced across participants. When women came for each evaluation, they provided weekly logs of their

Table 1 Sociodemographic profile for the three groups of participants Sociodemographic profile

HC

RA

FM

Age Mean S.D.

33 7.6

35 6.5

36 7.4

Education (highest level completed) (%) High school 4 College level 58 Graduate level 38

10 65 25

12 58 30

Employment status (%) Employed Not employed

92 8

75 25

80 20

Income (%) b US$0 – 29,999 US$30,000 – 69,999 N US$70,000

42 35 23

30 45 25

38 46 16

Partner status (%) Married, living w/partner Single, divorced, widowed

54 46

60 40

58 42

Children (%) 0 1 N1

54 13 33

60 10 30

53 16 31

HC = healthy controls, RA = rheumatoid arthritis, FM = fibromyalgia.

C. Alonso et al. / Journal of Psychosomatic Research 57 (2004) 451–458

menstrual status and pain symptoms for the week prior to the appointment date. In addition, on the date of their appointment, a pain assessment was conducted (tender point and dolorimeter assessments and self-reported pain levels). FM symptoms and negative and positive affect were also assessed on those two occasions. Participants received a total of US$200 for their time and participation at the end of the study. Measures Tender points All participants were assessed by palpation of the 18 tender points specified by the ACR in 1990 (see Fig. 1). Manual palpation was achieved by applying the right thumb on each tender point with a pressure of approximately 1 kg/s. Participants indicated when they first felt pain (as opposed to pressure), and tender point data are reported as the sum of positive tender points. Dolorimeter Dolorimetry evaluation was conducted with a pressure algometer. The algometer had a 1-cm-diameter rubber head, which was applied to 8 of the 18 ACR tender points and to 3 control points (right and left thigh and forehead; Fig. 1). Pressure on each point was increased at a rate of approximately 1 kg/s, and participants indicated when they first felt pain (as opposed to pressure). The reported dolorimetry score is considered a measure of pain threshold

Tender Points (18)

453

and reflects the mean of the eight sites examined. The mean of the three control points was also recorded and used for the analyses. The minimum score was 0 and was recorded for those women for whom the contact of the algometer with any of their eight tender or three control points was already painful (without any pressure). In contrast, if no pain was reported, the threshold maximum of 4 kg was recorded. Self-reported pain A visual analog scale (VAS) was used to assess subjective perception of pain based on a 10-cm line (0 no pain, 10 pain as bad as it could be). Pain diaries A pain diary was created using a modified version of the McGill Pain Questionnaire [21]. The short-form McGill Pain Questionnaire includes 15 descriptors of pain (11 sensory; 4 affective), which are rated on an intensity scale (0 = none, 1 = mild, 2 = moderate, 3 = severe), and VAS (0 = no pain, 10 = pain as bad as it could be). Participants filled out the daily questionnaire for 7 days prior to the hospital visit during both the follicular and luteal phases. Mood and anxiety symptoms The Mood and Anxiety Symptom Questionnaire-Short Form (MASQ; Ref. [22]) is a 62-item questionnaire that includes four scales, two of which assess general distress factors associated with anxiety and depression. The Anxious Arousal scale includes symptoms theorized to be specific to anxiety (such as somatic tension and hyperarousal), and the Anhedonic Depression scale was devised to be specific to depression (low positive affect, anhedonia).

Dolorimetry Points (8) Control Points (3)

Positive and negative affect The Positive and Negative Affect Schedule (PANAS; Ref. [23]) is a 20-item questionnaire that includes two 10item mood scales assessing Positive Affect (enthusiastic, active, alert) and Negative Affect (upset, guilty, afraid). FM symptoms The Fibromyalgia Impact Questionnaire (FIQ; Ref. [24]) is a 10-item questionnaire that measures physical functioning, work status, depression, anxiety, sleep, pain, stiffness, fatigue, and well-being. Using the listed items, we created five subscales, including days felt good (well-being), days missed work (work status), physical functioning, FM symptom score (sleep, pain, stiffness, fatigue), and negative emotion (depression, anxiety).

Fig. 1. Location of tender points, dolorimetry, and control pressure points (modified from Freundlich and Leventhal [34]).

Menstrual cycle symptoms The Menstrual Cycle Questionnaire (MCQ; Ref. [25]) is a 30-item standardized instrument including 23 questions about symptoms experienced during a typical menstrual cycle and questions regarding typical cycle and period length. Answers are rated on an intensity scale of 0 (does not apply to me) to 6 (extremely or intense).

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We used a global scale and also, based on the results of a factor analysis, created four subscales (premenstrual pain, perimenstrual negative affect, premenstrual water retention, and menstrual pain) to measure specific menstrual cycle symptoms. Data analysis To analyze the effect of menstrual phase on pain and affect, a series of repeated measures analyses of variance (MANOVAs) were conducted. For all the analyses, menstrual phase (follicular, luteal) was considered as a withinsubject variable and group (healthy controls, RA, FM) as a between-subjects variable. Post hoc analyses were based on the Tukey HSD test. Associations between pain and psychological variables were evaluated with Pearson’s r statistics, and Bonferroni corrections were applied for

Table 2 Means (M) and standard deviations (S.D.) of menstrual scores for the three groups of participants in relation to use of oral contraceptives (OC) Menstrual cycle characteristics

HC M

RA S.D.

M

FM S.D.

M

28.0 28.0 28.0

2.1 0.0 2.6

28.3 27.4 28.6

3.1 1.9 3.3

Typical menses length All 5.0 OC users 4.8 Non-OC users 5.0

1.4 0.9 1.5

4.5 3.9 4.9

1.5 1.8 1.3

5.1 4.9 5.1

1.1 1.0 1.2

Total menstrual symptoms All 33.4 OC users 30.9 Non-OC users 34.1

19.6 20.3 19.6

43.1 35.6 47.4

28.4 23.1 31.2

58.3a 65.2 55.5

24.8 17.3 26.2

1.2 1.2 1.3

1.6 1.0 1.9

1.6 1.0 1.8

2.7a 2.9 2.6

1.6 1.4 1.6

Perimenstrual negative affect All 2.0 OC users 2.0 Non-OC users 2.0

1.4 1.6 1.4

2.4 2.1 2.6

1.4 1.2 1.5

3.2b 3.3 3.2

1.6 1.6 1.6

Premenstrual water retention All 2.8 OC users 2.4 Non-OC users 2.9

1.6 1.7 1.6

3.2 2.9 3.4

1.6 1.8 1.5

3.7b 3.9 3.6

1.4 1.3 1.5

Menstrual pain All OC users Non-OC users

0.9 0.8 0.9

1.7 1.3 2.0

1.5 1.2 1.6

2.1b 2.4 1.9

1.2 1.0 1.2

1.1 0.9 1.1

RA

FM

Pain measures

M

S.D.

M

S.D.

M

S.D.

Tender point number (18 points) Dolorimetry (Kg., 8 points) Dolorimetry (Kg., 3 points) Visual analog scale (0-10) Pain diary

1.9

2.7

4.8

4.7

14.6a

2.5

3.7

0.5

3.2

0.8

2.0a

0.5

3.9

0.2

3.6

0.5

2.8b

0.7

0.4

0.6

2.3

1.9

4.8a

2.3

0.7

0.8

2.5

1.8

4.8a

1.8

a b

FM significantly different from both RA and HC. FM significantly different from HC.

multiple correlations. The SPSS 10.0 software package was employed for all the analyses.

Results Menstrual cycle characteristics

3.3 1.3 3.7

1.4 1.4 1.4

HC

S.D.

Typical cycle length All 29.2 OC users 28.4 Non-OC users 29.4

Premenstrual pain All OC users Non-OC users

Table 3 Means (M) and standard deviations (S.D.) of pain scores for the three groups of participants

HC = healthy controls, RA = rheumatoid arthritis, FM = fibromyalgia, OC = oral contraceptives. a FM significantly different from both RA and HC. b FM significantly different from HC.

Women in the three groups did not differ in typical cycle length or mean duration of menses. However, women with FM endorsed significantly more menstrual symptoms, in general, on the MCQ than did either women with RA and controls [ F(2,122) = 14.3, P b.001; Table 2]. In addition, women with FM also reported higher levels of premenstrual pain, negative affect, water retention, and menstrual pain on each of the four MCQ subscales (all Ps b .02). It is important to note that for the three groups, the use of oral contraceptives did not have a significant effect on typical cycle length, mean duration of menses, total menstrual symptoms, or on any of the four MCQ subscales (see Table 2). Pain Consistent with their diagnosis and reports of increased pain, a series of analyses of variance (ANOVAs) indicated that women with FM had more positive tender points and were less able to tolerate the dolorimetry pressure than did women with RA and the healthy control women (all Ps b .001; Table 3). Women with FM had a mean of 14.6 positive tender points, whereas the RA and healthy control women had 4.8 and 1.9, respectively. RA and healthy control women tolerated significantly more dolorimetry pressure both at the eight tender point locations, as well as at the three control points. The latter difference indicates that women with FM are also more sensitive to pain in areas other than the 18 utilized in the standard diagnostic test. When analyzing all pain measures for the entire sample of women, tender points, dolorimeter scores, self-reported pain, and the pain diary scores were significantly correlated. However, when considering the FM women separately, only

C. Alonso et al. / Journal of Psychosomatic Research 57 (2004) 451–458

455

80

HC RA FM

HC RA

18

Total Number of Tender Points

70

FM

MASQ Score

60 50 40 30 20

16 14 12 10 8 6 4 2 0 Follicular

10 GDA

GDD

AA

AD

MASQ Subscales Fig. 2. Means (mS.E.) of depression and anxiety scores for the three groups of participants. HC = healthy controls, RA = Rheumatoid Arthritis, FM = fibromyalgia, MASQ = Mood and Anxiety Symptom Questionnaire, GDA = general distress anxious symptoms, GDD = general distress depressive symptoms, AA = anxious arousal, AD = anhedonic depression.

the correlations between tender points and dolorimeter scores and between the VAS and pain diary scores remained significant at the P b.001 level (tender points and eight dolorimetry locations: r = .53; tender points and three dolorimetry control locations: r = .49; VAS and pain diary scores: r = .78). Positive and negative affect Women with FM reported higher levels of both general and specific symptoms of anxiety and depression, as measured by the MASQ (Fig. 2), and more negative and

Table 4 Correlations among affect, pain, and menstrual symptoms for the three groups of participants Pain and menstrual symptoms Tender point number (18 points) Dolorimetry (Kg., 8 points) Dolorimetry (Kg., 3 control points) Visual analog scale (0 – 10) Pain diary Total menstrual symptoms

PANAS NA

MASQ PA

AA

Luteal

Menstrual Phase

GDA

GDD

.47

.36

.59

.44

.62

AD .47

.40

.34

.51

.38

.54

.43

.23

.22

.38

.25

.46

.29

.50

.45

.60

.48

.54

.52

.47 .40

.51 .28

.60 .49

.49 .32

.59 .52

.56 .34

Correlations greater than .30 are statistically significant at P b.001 with the Bonferroni adjusted probability for multiple comparisons. PANAS = Positive and Negative Affect Schedule, MASQ = Mood and Anxiety Symptom Questionnaire, NA = negative affect, PA = positive affect, GDA = general distress anxious symptoms, GDD = general distress depressive symptoms, AA = anxious arousal, AD = anhedonic depression.

Fig. 3. Mean (mS.E.) number of tender points for the three groups of participants during the follicular and luteal phases. HC = healthy controls, RA = rheumatoid arthritis, FM = fibromyalgia.

less positive affect on the PANAS than did RA and healthy control women (all Ps b .001). Across all participants, negative affect scores from the PANAS were significantly correlated with the total number of tender points (r = .46, P b.001) as well as with overall menstrual pain (r = .40, P b.001). Similarly, positive affect was inversely correlated with total number of tender points (r = .36, P b.001) and with overall menstrual pain (r = .28, P b.003). In addition, depression and anxiety scores from the MASQ were also significantly correlated with menstrual pain and tenderness (Table 4). Menstrual variation in pain and affect To analyze the effect of menstrual phase on pain and affect, a series of MANOVAs were conducted. FM participants evinced consistently higher levels of pain sensitivity or self-reported more pain during both phases of the cycle1. This invariant pattern of more tender points across the cycle is illustrated in Fig. 3. Similarly, none of the other four pain measures varied significantly across the menstrual cycle for any of the three groups of participants. However, there was a nonsignificant trend for greater sensitivity to dolorimetry pressure for all participants during the luteal phase of the menstrual cycle [ F(2,122) = 3.55, P b.07], suggesting that women, in general, were able to tolerate less pressure from the dolorimeter at that time of the month. While the pain indices were relatively constant across the menstrual cycle, there was a striking shift in emotionality. A

1 Because a high percent of the healthy controls endorsed no pain on the VAS and thus received a 0 score, the results were analyzed with both parametric and nonparametric statistics. The Friedman nonparametric test yielded the same outcome as the MANOVA did, indicating just an effect of group and no differences between the two time periods.

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C. Alonso et al. / Journal of Psychosomatic Research 57 (2004) 451–458 HC RA FM

PANAS Positive Affect Score

40

30

20

10

0 Follicular

Luteal

Menstrual Phase Fig. 4. Means (mS.E.) of positive effect scores for the three groups of participants during the follicular and luteal phases. HC = healthy controls, RA = rheumatoid arthritis, FM = fibromyalgia, PANAS = Positive and Negative Affect Schedule.

main effect for menstrual phase indicated that all women reported less positive affect during the luteal phase in comparison to the follicular phase [ F(2,122) = 4.76, P b.04]. Furthermore, post hoc tests indicated that women with FM and with RA reported significantly less positive affect during the luteal phase than did the controls [ F(2,122) = 3.60, P b.04; Fig. 4]. Based on the MASQ scale, there were some similar trends suggesting that women, in general, seemed to experience more symptoms of anhedonic depression during the luteal phase [ F(2,122) = 3.80, P = .05]. Post hoc tests indicated that this increase in depressive symptomatology was more accentuated in women with FM as compared with control women ( P b.001) and that women with RA also experienced significantly more anhedonic depression than did controls during the luteal phase of the cycle ( P b.008).

Discussion The aim of the present study was to examine the effects of the menstrual cycle in women with FM and RA. Our findings emphasize the importance of considering menstrual cycle variation for understanding the relationship between pain and emotion. Despite similarities in the temporal aspects of the menstrual cycle, in terms of cycle length and duration of menses, the FM participants reported higher levels of premenstrual discomfort and dysmenorrhea. This is consistent with many reports suggesting that women with FM have greater sensitivity to painful stimuli and, perhaps, are even more likely to anticipate that potentially painful experiences will actually be painful

[26]. Nevertheless, we did not find that the specific painful symptoms associated with FM, in terms of the diagnostic tender points, varied across the follicular and luteal phases. This result concurs with those studies that also found consistent and persistent pain across the cycle [5] but differs from reports of hyperalgesia during the follicular [4] or luteal [7] phase. Although it has been reported that reproductive hormones can affect pain perception in other pain conditions, such as myofascial pain [27], in our sample of FM women and in a previous study involving college students [28], we did not find an effect of oral contraceptives on the menstrual pain. More dramatic than any change in the objective measures of pain, however, were the shifts in psychological state, especially with regard to the decrease in positive affect during the luteal phase. Consistent with Anderberg et al. [7], we found that women with FM experienced less positive affect than did the other two groups of women during the luteal phase. This result supports previous work that has emphasized the importance of measuring not only the presence of negative affect, but also the absence of positive affect in chronic pain [29] and in depressed patients [30]. Because women with FM are more likely to de depressed or anxious, a rise in dysphoric mood, accompanied by less positive emotion, might alter the experience and tolerance for pain, as well as color how the individual presents to the treating clinician. Consistent with the FM diagnosis, these women reported higher levels of pain, had more positive tender points, and were less able to tolerate the pressure from the dolorimeter than were women with RA and healthy control women. It is also important to highlight that women with RA were intermediate in these pain evaluations and that our sample of mild RA averaged only 4.8 tender points, significantly below the cutoff of 11 used as diagnostic criterion for FM. These RA participants also reported less premenstrual and menstrual discomfort than did the FM participants. While our exclusion criteria for RA, which included the use of steroidal medications, prevented us from recruiting women with more severe disease, this finding of a difference in pain sensitivity and tolerance when compared with FM concurs with other papers (e.g., Ref. [18]). Moreover, our psychological evaluations of women with these two conditions yielded similar differences, with a greater likelihood of depressive and anxious symptoms in FM. However, it should be reiterated that some shift in general mood across the cycle was evident in many women from the three groups, including the healthy controls. Our analyses from the PANAS and MASQ instruments indicated that there was a significant tendency for more negative and less positive affect during the luteal as compared with the follicular phase. Because women with FM already show a bias for dysphoric mood, when compared with RA and healthy women, this type of monthly variation would tend to make a shift in emotional state of greater clinical significance. From a statistical point of view, the change in

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psychological well-being from the follicular to the luteal phase was not greater in women with FM, but the lability in mood could be pronounced in certain patients. Indeed, if one considers that the pain associated with menstruation would be summative with the generic body pain and tenderness in FM, then these women may have an added pain burden to tolerate. Nevertheless, with regard to our initial and specific hypothesis, we did not replicate the conclusion that FM pain is greater during the luteal phase [7,12]. Thus, our study supports the conclusions of Johns and Littlejohn [5] and Macfarlane et al. [13]. Several factors may have influenced our findings, including the specific way of defining the cycle phases. We focused on the early follicular phase and may have missed some remission in symptoms closer to ovulation. Similarly, our scheduling during the luteal phase did not restrict visits to the days immediately before menses. Thus, we may have missed an accentuation of FM symptoms in conjunction with dysmenorrhea during the perimenstrual days. Because our study was designed to investigate the dual influence of emotional state and menstrual phase primarily, we also did not consider some other important factors known to affect the experience and tolerance for pain. For example, exercise can affect both premenstrual symptoms and dysmenorrhea, and, because of their pain, individuals with FM and RA would be less likely to exercise or would do so in a modified way [31-33]. We and others have also reported that social relationships and, in particular, disruptions of social support can influence the subjective experience and tolerance for dysmenorrhea, even in healthy young women [28]. This may reflect a direct effect of psychological state on hormone and pain-related physiology or, perhaps, the ways in which mood and outlook can sensitize or minimize the attention given to symptoms. Finally, because our sample was composed of women who responded to an announcement of our study, there is a potential for selection bias as compared with a clinic population. In sum, the critical finding of this study was that FM pain was relatively constant across the cycle, but that our participants were more likely to report the occurrence of additional premenstrual pain and dysmenorrhea. With respect to temporal variation, a cyclical shift in mood was perhaps the more important domain to vary, and it was most manifest by a decrease in positive affect. The resulting dysphoria might undermine an individual’s ability to tolerate painful symptoms and could color presentation to a clinician. Indeed, one could imagine that the diagnostician might be biased to perceive a worsening of disease, unless they used objective and quantifiable measures of pain, such as dolorimetry. Finally, our results point to the importance of considering specific interventions designed to increase positive affect not only in general, but especially during the luteal phase, when designing interventions to improve the psychological well-being of women with FM.

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Acknowledgments Special acknowledgments are due to Holly Schleicher and Julie Surbaugh for the invaluable assistance with participant recruitment, evaluations, and data analyses.

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[20]

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