Pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage” (Merskey & Bogduk, 1994, p. 226). This definition suggests pain is not limited to physical senses, and is consistent with the claim that pain has sensory and affective aspects (Melzack, 1987; Price, 2000), which have been reported to be independent of each other in many respects (Cano, 2004; Crombez, Van Ryckeghem, Eccleston, & Van Damme, 2013; Di Tella et al., 2017; Loeser & Melzack, 1999). The sensory aspect of pain is responsible for pain intensity, whereas its affective aspect is responsible for unpleasant emotional responses before, during, and after experiencing actual or imagined pain (Boggero & Carlson, 2015). Sensory pain is involved in the protection and recovery of injured areas, whereas affective pain contributes to the avoidance of similar situations and to the induction of social support (Cano, 2004; Loeser & Melzack, 1999). In addition, sensory pain is affected by rapidly conducting spinal systems, whereas affective pain is affected by the brainstem reticular formation and the limbic system (Di Tella et al., 2017).

Both sensory and affective pain have negative effects on pain-related conditions, such as depression, anxiety, and decreased daily function (Boggero & Carlson, 2015). Of the many pain-related variables, pain catastrophizing has emerged as an important factor in the maintenance and exacerbation of pain (Quartana, Campbell, & Edwards, 2009). Pain catastrophizing is defined as exaggerated negative mental activity that occurs during the expectation of pain or actual pain experience (Sullivan et al., 2001). It is a unique phenomenon that can be expressed by magnification, that is, by the individual exaggerating the threatening value of painful stimuli, by helplessness, that is, negatively assessing his or her ability to handle painful stimuli, and rumination, that is, being unable to suppress pain-related thoughts (Sullivan, Bishop, & Pivik, 1995). Pain catastrophizing is associated with pain intensity, depression, anxiety and pain-related disability (Keefe et al., 2000; Sullivan et al., 1995; Sullivan, Stanish, Waite, Sullivan, & Tripp, 1998; Sullivan et al., 2001).

In the fear-avoidance model a clearer path is presented to the relationship between pain and pain catastrophizing (Vlaeyen & Linton, 2000). According to this model, the manner in which individuals interpret and respond to pain affects their future pain experiences (Schütze, Rees, Preece, & Schütze, 2010). When people suffer pain, they become afraid of pain, and even avoid behaviors that might provide relief from pain, because of their negative perceptions of pain (e.g., pain catastrophizing). As a result, pain, pain catastrophizing, and maladaptive pain outcomes create a pain chain whereby pain is maintained and deepened, and pain catastrophizing is a critical factor in this pain chain (Sullivan et al., 1995). The importance of pain catastrophizing to the development and maintenance of this pain chain is also evident in the treatment of pain. During multidisciplinary treatments, reducing pain catastrophizing is regarded as a key treatment factor (Quartana et al., 2009).

Sensory and affective pain may exert different effects on pain catastrophizing. Theoretically, the catastrophizing of pain may have its roots in a stable pain schema consisting of beliefs that pain is harmful, horrible, and disastrous, with few innocuous sensory aspects of pain stimuli. Accordingly, people with high pain catastrophizing will be more vulnerable to the affective aspect of pain because the information is consistent with their pain schema (Michael & Burns, 2004). Consistent with these arguments, in a study conducted by Geisser, Robinson, Keefe, and Weiner (1994) the results indicated that the relationship between depression and affective (but not sensory) pain was mediated by pain catastrophizing. Given that sensory and affective pain have different characteristics, mechanisms, and influences on pain catastrophizing, they need to be studied separately. However, they cannot be seen as completely separate. Boggero and Carlson (2015) showed that the interaction of sensory and affective pain predicts pain interference better than each individual pain aspect does. This result suggests a synergistic effect of sensory and affective pain. However, the relationship between different aspects of pain and pain catastrophizing has not been directly studied.

Given that sensory and affective pain may have a synergistic effect, the mechanism via which they affect pain catastrophizing requires investigation. In addition to the interaction of the different  aspects of pain, research findings suggest that pain and pain catastrophizing could be dependent on gender (Jensen, Nygren, Gamberale, Goldie, & Westerholm, 1994; Keefe et al., 2000; Keogh, Hatton, & Ellery, 2000; Keogh & Herdenfeldt, 2002; Lynch, Kashikar-Zuck, Goldschneider, & Jones, 2007). Some researchers have suggested that women report greater pain sensitivity and pain catastrophizing than do men (Madsen et al., 2018; Wiesenfeld-Hallin, 2005). In another study (Keefe et al., 2000), it was found that attention toward pain was effective in reducing sensory pain in men, but not in women. This result suggests that effective strategies for reducing pain in men and women may be different. The difference in effectiveness of these strategies may be because of differences in gender socialization between women and men. Compared to women, men are rewarded more for gender-congruent behavior, and ignored or punished more for gender-incongruent behavior (Myers, Riley, & Robinson, 2003). This suggests that men may have developed certain behaviors with regard to coping with pain as a means of conforming to strict social stereotypes, and that the way that men and women cope with pain may be different. These results from previous studies, combined with differences in gender socialization, imply that consideration of gender might improve understanding of the relationship between pain and pain catastrophizing.

In the present study, we considered the differences and interactions in pain aspects and gender differences in pain experience and the approach to pain, and examined how the interaction of sensory pain and affective pain affects pain catastrophizing according to gender. We hypothesized that sensory pain would interact with affective pain, and that this interaction would be associated with greater pain catastrophizing in men than in women.

Method

Design

We performed this cross-sectional, descriptive, correlation study to determine whether or not the independent and interactive effects of sensory pain and affective pain on pain catastrophizing in people with chronic pain are gender dependent.

Participants

The study participants were 170 people (men = 63, women = 107) who were receiving treatment for chronic pain at a university pain clinic in Daegu, Republic of Korea. The study inclusion criterion was at least a 3-month history of recurrent or persistent pain. Demographic and clinical characteristics of the study participants are provided in Table 1.

The size of the study sample was calculated using G*Power 3.1 program (Faul, Erdfelder, Lang, & Buchner, 2007), based on medium effect size (f² = .15), a statistical power of 80% at a two-tailed significance level of 5%, and three predictors by linear regression analysis. The calculated minimum sample size was 77 patients, which was slightly larger than the number of male participants in our study, but the number of women was sufficient.

Measures

The short-form McGill Pain Questionnaire (SF-MPQ; Melzack, 1987) is a 15-item self-report measure designed to assess sensory (11 items) and affective (four items) pain experiences. We used a Korean version of the SF-MPQ (Choi, Son, Lee, & Cho, 2015). Each item is rated on a 4-point scale ranging from 0 (none) to 3 (severe). Total possible scores range from 0 to 33 for sensory pain and from 0 to 12 for affective pain, and higher scores represent greater pain. The internal consistencies of the Korean version of the SF-MPQ, as determined in a validation study, were α = .90 for sensory pain and α = .91 for affective pain (Melzack, 1987). Internal consistencies for sensory and affective pain in the current study were α = .80 and .71, respectively.

The Pain Catastrophizing Scale (PCS; Sullivan et al., 2001) is a 13-item self-report measure designed to assess three subscales of catastrophizing: helplessness (six items), magnification (three items), and rumination (four items). We used a Korean version of the PCS (Cho, Kim, & Lee, 2013). Each item of the PCS is rated on a 5-point scale ranging from 0 (not at all) to 4 (all the time). Possible total scores range from 0 to 24 for helplessness, from 0 to 12 for magnification, and from 0 to 16 for rumination, where higher scores represent a greater degree of the type of catastrophizing in the three subscales. The internal consistencies as determined in the validation study of the Korean version of the PCS for helplessness, magnification, and rumination were α = .90, .71, and .86, respectively (Cho et al., 2013). In the present study, corresponding internal consistencies were α = .92, .76, and .76, respectively.>

Ethical Considerations

The study was approved by the Institutional Review Board of Keimyung University Hospital, located in Daegu, Republic of Korea (IRB No. 2015-08-037-003). Before study commencement, we fully explained its purpose and method to prospective participants, ensured personal information was secured and protected, and assured participants that they could withdraw from the study at any time without prejudice. All data were obtained appropriately after participants had provided informed consent.

Data Analyses

The analyses were performed using SPSS v. 18.0 for Windows. Demographic and clinical characteristics of the men and women were compared using the two-sample t test for continuous variables (i.e., age, sensory pain, affective pain, pain catastrophizing) or the chi-square test for categorical variables (i.e., education level, pain medication, financial compensation because of pain, pain-related litigation). Pearson product moment correlations were calculated to examine the relationships among study measures. Three hierarchical multiple regression analyses for both genders were conducted to examine the effects of sensory pain, affective pain, and their interaction on the three components of pain catastrophizing, that is, helplessness, magnification, and rumination. Sensory pain and affective pain were centered to reduce multicollinearity between both aspects of pain and their interactions (Holmbeck, 2002). During Step 1, the main-effect terms (sensory pain and affective pain) were entered, followed by the interaction terms (sensory pain × affective pain) during Step 2. Significant interactions were probed using the PROCESS script for SPSS (Hayes, 2013).

Results

Except for a marginally significant result for sensory pain, no significant differences were found between the demographic or clinical characteristics of the men and women (Table 1). Moderate positive correlations were observed between sensory and affective pain and all subscales of pain catastrophizing, which suggested higher levels of pain were associated with higher levels of pain catastrophizing (Table 2).

The regression results for men are presented in Table 3. The main-effect terms (sensory and affective pain) significantly enhanced the predictions of all pain catastrophizing subscales. Regression coefficients for sensory pain were significant in the equations for helplessness, magnification, and rumination and those for affective pain were significant in the equations for helplessness and magnification, but not rumination. The interaction term (sensory pain × affective pain) also significantly enhanced the predictions of all pain catastrophizing subscales.

Subsequently, the interactions were probed and calculated at a 95% confidence interval (CI). For helplessness, significance was identified at a low (minus one standard deviation) level of affective pain, b = .56, SE = 0.13, p < .001, 95% CI [0.29, 0.81], at an average level of affective pain, b = .40, SE = 0.10, p < .001, 95% CI [0.20, 0.61], and at a high (plus one standard deviation) level of affective pain, b = .25, SE = 0.11, p < .05, 95% CI [0.03, 0.46]. For magnification, significance was identified at a low (minus one standard deviation) level of affective pain, b = .28, SE = 0.08, p < .01, 95% CI [0.11, 0.45], and at an average level of affective pain, b = .19, SE = 0.07, p < .01, 95% CI [0.06, 0.32], but not at a high (plus one standard deviation) level of affective pain, b = .09, SE = 0.07, p = .19, 95% CI [-0.05, 0.23]. For rumination, significance was identified at a low (minus one standard deviation) level of affective pain, b = .47, SE = 0.14, p < .01, 95% CI [0.20, 0.76], and at an average level of affective pain, b = .31, SE = 0.11, p < .01, 95% CI [0.09, 0.53], but not at a high (plus one standard deviation) level of affective pain, b = .14, SE = 0.11, p = .22, 95% CI [-0.08, 0.37]. These findings indicate that higher levels of sensory pain are associated with greater pain catastrophizing at low and average levels of affective pain.

The regression results for women are presented in Table 3. The main-effect term (sensory pain and affective pain) significantly increased the prediction of all pain catastrophizing subscales. The regression coefficients for affective pain were significant in the equation for helplessness, magnification, and rumination, but those for sensory pain were not, and the interaction term (sensory pain × affective pain) did not add a significant increment to the prediction of any of the three pain catastrophizing subscales.

Discussion

We investigated the influence of the gender of people being treated for chronic pain, on the effects of the sensory and affective aspects of pain on pain catastrophizing. We found that, for men, at low and average levels of affective pain, higher levels of sensory pain were associated with greater pain catastrophizing, but sensory pain had little effect on pain catastrophizing only at high levels of affective pain. On the other hand, for women, higher levels of affective pain were associated with greater pain catastrophizing, regardless of the degree of sensory pain. These results suggest that, among people being treated for chronic pain, for sensory pain, affective pain, and their combination there may be gender-dependent effects on pain catastrophizing.

Research findings have consistently shown that women report greater pain and more negative responses to pain than do men (Keogh & Herdenfeldt, 2002). However, we were interested that, in our study, with the exception of a marginally significant gender difference for sensory pain, differences between pain and pain catastrophizing in the men and women were nonsignificant. Furthermore, the men in our study reported more sensory pain than did the women. These findings suggest that gender-dependent relationships between pain aspects and pain catastrophizing are not as straightforward as they might have appeared. As has been previously reported, men and women tend to cope with pain experiences differently, with men adopting a problem-solving approach, whereas women focus on interpersonal and emotional aspects of situations (Robinson, Riley, & Myers, 2000). Given that chronic pain management in Korea is limited to treatment to achieve the reduction of sensory pain (Cho, Lee, McCracken, Moon, & Heiby, 2010), men’s coping strategies seem to be consistent with the Korean primary goal of pain care. However, failure to reduce sensory pain may exacerbate negative cognitive–affective responses to pain (i.e., pain catastrophizing), even at low levels of affective pain. On the other hand, women’s coping strategies seem to be inconsistent with the primary goal of pain care in Korea, and this unmet need in current pain care is likely to exacerbate pain catastrophizing. Thus, it may be necessary, when treating women, for health-care providers in Korea to focus on reducing affective pain rather than on the reduction of sensory pain. Unfortunately, in Korea there is a shortage of health professionals capable of providing such support, and women (as well as men) do not even recognize the need for this type of assistance.

In the present study, the affective aspect of pain was found to be related to pain catastrophizing regardless of gender, which suggests that affective, rather than sensory pain plays an important role in pain catastrophizing. Pain is a conglomerate of unpleasant sensory and emotional experiences, and is not often purely proportional to physiological causes (Davis & Walsh, 2004). Affective pain may be responsible for this divergence, given that it involves secondary unpleasantness derived from sensory pain (Fields, 1999). Such features of affective pain may readily facilitate pain catastrophizing and negative cognitive–affective responses (helplessness, magnification, and rumination). Pain catastrophizing is a recognized critical factor in pain treatment outcomes (Turk & Okifuji, 2002). In the fear-avoidance model, pain catastrophizing is preceded by pain (experience), and the present study findings therefore highlight the importance of early intervention to prevent the establishment of a vicious cycle.

The study findings provide insights for improving clinical applications. For pain catastrophizing, our results show men are affected by both affective and sensory aspects of pain, and women are affected by affective pain. This suggests that approaches to pain catastrophizing need to be specifically tailored for men and women. In general, the primary concern of patients with chronic pain and of health professionals in Korea is the reduction of sensory pain (Cho et al., 2010). Therefore, the focus in most clinical approaches is on medications, medical procedures, or surgery. However, our findings demonstrate the need for additional interventions for affective pain. Given that context and cognitive appraisal have significant impacts on affective pain (Horn, Blischke, Kunz, & Lautenbacher, 2012), Korean health professionals need to be able to offer the appropriate psychological services to their patients who suffer from chronic pain. To this end, it is essential that patients with chronic pain are able to discriminate between the two aspects of pain. For example, mindfulness training can be used to help people to observe their pain as it is.

The limitations of this study are as follows. First, the relatively small sample size of the group of male participants may have reduced the statistical power of the results. Second, because of the cross-sectional nature of this study, and given the vicious cycle of the fear-avoidance model (Vlaeyen & Linton, 2000), it was difficult to interpret the results causally. Third, the study cohort was composed of patients with heterogeneous pain problems who were receiving treatment at a single tertiary pain clinic. Thus, our results cannot be generalized to patients in other health care systems (i.e., primary and secondary) or patients with specific pain-related problems. Fourth, depression and other mental health issues may overlap with affective pain and the pain may be psychosomatic rather than related to actual physical pain. However, we did not control for these possibilities in our participant group in our analyses.

In conclusion, in this study we have provided evidence that the gender of people suffering from chronic pain influences the effects of pain aspects on pain catastrophizing. According to our results, affective pain appears to play a major role in pain catastrophizing, regardless of gender and, for men, the role of sensory pain in pain catastrophizing requires consideration. Given that pain catastrophizing critically affects pain treatment outcomes (Turk & Okifuji, 2002), our findings suggest that more attention should be paid to the affective aspect of pain when treating people with chronic pain. Future research is required to confirm our results and to investigate their relevance in clinical practice.

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This paper was supported by the Post-Retired Research Professor research funds of Chonbuk National University in 2016.

Sungkun Cho, Department of Psychology, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea. Email: [email protected]