Alexithymia and fear of pain independently predict heat pain intensity ratings among undergraduate university students

1Department of Psychology; 2School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, Ontario Correspondence: Dr Joel Katz, Department of Psychology, Behavioral Sciences Building, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3. Telephone 416-736-2100 ext 40557, fax 416-736-5814, e-mail jkatz@yorku.ca Over the past decade, alexithymia and its relationship to pain has become a focus of intense research. Alexithymia is a multidimensional construct (1,2) that refers to cognitive and emotional disturbances (3) characterized by four attributes – problems recognizing and explaining emotions, problems distinguishing between emotional and physical sensations, restricted imagination, and externally focused and concrete cognitive style (3-5). Research has shown that patients with chronic pain have higher levels of alexithymia than healthy controls, and alexithymia is associated with over-reporting physical symptoms (eg, somatic complaints, anxiety, and hypochondriasis) (6). Research conducted on healthy subjects has also demonstrated an association between alexithymia and increased pain intensity and sensitivity in laboratory studies of experimentally induced pain (7-9) and in a community sample of originAl Article

Results from these studies highlight the importance of alexithymia in the pain experience.However, most research examining pain and alexithymia has been conducted in isolation from other psychological factors (11)(12)(13) recognized as integral to the pain experience.Research supports the importance of anxiety sensitivity (14,15), fear of pain and pain anxiety (16)(17)(18)(19), pain avoidance (20,21), and pain catastrophizing (22,23) in the expression of pain and pain-related disability.These constructs have been the focus of recent models of pain, such as the diathesis-stress model of chronic pain and disability (24).
According to this model (24), individuals who are high in anxiety sensitivity (diathesis) and who are exposed to a painful trauma or event (stress) are likely to develop chronic pain and disability through well-articulated cognitive and emotional processes involving fear and avoidance (eg, fear of pain, catastrophizing, self-efficacy, and escape-avoidance) (25).Despite the growing body of research demonstrating the relationship between alexithymia and pain, there is very little integration of these findings with existing models of pain, such as Turk's diathesisstress model (24).An exception is the study by Lumley et al (26), which examined the relationship between alexithymia, self-efficacy, catastrophizing, depression, and pain severity and impairment in patients with chronic myofascial pain.Alexithymia showed a moderate to strong correlation with self-efficacy, catastrophizing, and depression, and was also associated with pain affect and impairment, but not with pain sensitivity (26).
The objective of the current study was to examine the relationship between alexithymia and integral components of the pain experience highlighted in Turk's diathesis-stress model of chronic pain and disability (24).The relationships among alexithymia, fear of pain, anxiety sensitivity, pain avoidance, catastrophizing, sex, and heat pain intensity were assessed in a sample of undergraduate university students.

Participants
The study sample comprised 67 undergraduate students (44 women and 23 men) 17 to 45 years of age, who had a mean (± SD) age of 20.39±3.77years, and were proficient in English.Individuals received course credit for their participation.
heat pain stimuli and subjective pain ratings Thermal stimuli were delivered using a Peltier thermode with a skin contact surface of 16 mm 2 (TSA-III NeuroSensory Analyzer; Medoc Ltd, Israel).This computerized device is capable of generating heat or cold stimuli that range from approximately 0°C to 50°C.Pressing a button stops the rise or drop in temperature and the thermode rapidly returns to room temperature at a rate of 10°C/s.Even at the extreme high (50°C) and low (0°C) temperatures, the thermode does not damage the skin, although participants may temporarily feel sensitive at the site where the thermode is applied.
The contact thermode was applied to the ventral aspect of the participant's nondominant forearm and affixed in place with a Velcro strap (Velcro USA Inc).Consistent with previous work in magnitude estimation of thermal stimuli (27), four suprapain threshold heat stimuli (46°C, 47°C, 48°C, and 49°C) were administered in random order.All trials began at a baseline temperature of 32°C, increased at a rate of 4°C/s and remained at the preset peak temperature for a duration of 5 s.A 30 s interval was maintained between successive stimuli to avoid sensitization of cutaneous receptors.During the 5 s period when the thermode reached its peak temperature, participants were asked to rate the intensity of the pain they experienced on a numerical rating scale (NRS) ranging from no pain at all (0) to the most intense pain imaginable (100).These temperatures were selected to be consistent with previous work (27) and to ensure that these stimuli were above the mean heat pain threshold (as previously established in these subjects; data not shown).

Questionnaires Anxiety sensitivity index:
The Anxiety Sensitivity Index (ASI) ( 28) is a widely used, 16-item scale that measures concerns that anxiety and anxiety-related symptoms will lead to harmful negative consequences.Each item is rated on a fivepoint scale ranging from 0 (very little) to 4 (very much).The ASI yields a total score and three factor analytic-derived subscale scores, including fear of somatic symptoms/physical concerns, fear of cognitive symptoms/mental incapacitation concerns, and fear of publicly observable symptoms/social concerns (29).The ASI demonstrates good test-retest reliability (r=0.72) and research demonstrates some evidence for the discriminant validity of the three subscales among anxiety disorder outpatients (30).The internal consistency of the ASI in the present study was excellent (alpha = 0.87).Pain Catastrophizing scale: Pain catastrophizing is characterized by unrealistic beliefs that the current situation will lead to the worst possible pain outcome (31), negative thoughts about the future and self (24), and "an exaggerated negative 'mental set' brought to bear during actual or anticipated pain experience" (32).The Pain Catastrophizing Scale (PCS) (33) consists of 13 items describing thoughts and feelings that individuals may experience when they are in pain.Each item is rated on a five-point scale ranging from 0 (not at all) to 4 (all the time).The PCS yields a total score and three subscale scores assessing rumination, magnification, and helplessness.The PCS demonstrates adequate to excellent internal consistency in community (alpha = 0.88 to 0.95) and pain outpatient samples (alpha = 0.75 to 0.92) (34).The PCS has moderate convergent validity; the correlation coefficient between the PCS and a self-report measure of anxiety is r=0.32 and negative affectivity is r=0.70 (33).The PCS shows good test-retest reliability at six (r=0.75) and 10 (r=0.70)weeks (33).The internal consistency of the PCS in the present study was excellent (alpha = 0.92).

Pain Anxiety symptoms scale-20:
The Pain Anxiety Symptoms Scale-20 (PASS-20) ( 35) is a shortened 20-item version of the original 40-item PASS (36) designed to assess fear and anxiety responses specific to pain.The PASS-20 consists of four five-item subscales, including cognitive anxiety responses, escape and avoidance, fearful thinking, and physiological anxiety responses.Each item is rated on a six-point scale ranging from 0 (never) to 5 (always), with total scores ranging from 0 to 100.The PASS-20 has been shown to have good internal consistency (alpha = 0.81) and good convergent validity with the original 40-item PASS (r=0.95) (35).Concurrent validity of the PASS-20 is demonstrated through its moderate to high correlations with related measures such as anxiety sensitivity (ASI; r=0.56), fear of pain (Fear of Pain Questionnaire III [FPQ-III]; r=0.53), and pain catastrophizing (PCS; r=0.38) (37).The internal consistency of the PASS-20 in the present study was excellent (alpha = 0.93).Consistent with previous research (38,39), the escape and avoidance subscale of the PASS-20 (PASS-AVO) was used as a measure of pain avoidance.

FPQ-iii:
The FPQ-III ( 40) is a 30-item self-report measure designed to assess fear of pain in nonchronic pain populations.The FPQ-III assesses fear of severe pain, fear of minor pain, and fear of procedural pain due to medical interventions.Each item is rated on a five-point scale ranging from 1 (not at all) to 5 (extreme).The FPQ-III has good internal consistency (alpha = 0.88 to 0.92) and test-retest reliability (r=0.69 to 0.74) at three-week follow-up (40).Furthermore, high fear of pain scores correlate significantly with avoidance/escape behaviour during a pain-relevant Behavioral Avoidance Test, suggesting predictive validity (40).The internal consistency of the FPQ-III in the present study was excellent (alpha = 0.89).toronto Alexithymia scale-20: Alexithymia is a construct that describes a personality style characterized by deficits in the subjective awareness and cognitive processing of affect (41).The Toronto Alexithymia Scale-20 (TAS-20) ( 42) is a 20-item self-report inventory that measures three dimensions of alexithymia -difficulty identifying feelings, difficulty describing feelings, and externally oriented thinking.Each item is rated on a five-point scale ranging from 1 (strongly disagree) to 5 (strongly agree).Total TAS-20 scores range from 20 to 100.The TAS-20 demonstrates good internal consistency (alpha = 0.70 to 0.86) (43) and test-retest reliability (r=0.77) over a three-week period (42).The internal consistency of the TAS-20 in the present study was good (alpha = 0.80).nRs for pain intensity: Pain intensity in response to the four heat pain stimuli was measured using a self-report NRS (44).The NRS consists of a series of numbers ranging from 0 ('not at all') to 100 ('the most pain imaginable').Participants were asked to choose the number that best corresponded to the intensity of each heat pain stimulus.The NRS is commonly used in clinical settings (45) and is the preferred pain rating scale among patients (46).The NRS is highly correlated (r=0.94) with the visual analogue scale (45) and is sensitive to change following pharmacological interventions (44).

Procedure
The research study was reviewed and approved by the Human Participants Review Committee at York University (Toronto, Ontario).Following informed written consent, participants underwent thermal sensory testing and completed the ASI, PCS, PASS-20, FPQ-III, and TAS-20.The order of administration of questionnaires was randomized within participants.The order of thermal testing and questionnaire completion was counterbalanced across participants such that one-half of the participants underwent thermal testing and then completed the questionnaires, and the other one-half completed the questionnaires followed by the thermal testing.

ResuLts descriptive statistics
Means and SDs of each score are presented on the main diagonal of Table 1.Scores on the TAS-20, PCS, PASS-AVO, and FPQ-III were similar to those obtained in large community samples.Ten per cent of participants (n=7) in the present study had scores on the TAS-20 above the cut-off score of 61 or greater that corresponds with clinical levels of alexithymia (47).Scores on the ASI were higher compared with scores obtained in other community samples (eg, mean ASI score 21.85±10.14 in reference 48).Correlations between average pain intensity across the four heat pain stimuli, anxiety sensitivity, fear of pain, pain catastrophizing, pain avoidance, alexithymia, and sex are presented in Table 1.Pain catastrophizing, pain avoidance, and sex were not significantly correlated with average pain intensity.

Relationship between alexithymia and average pain intensity after controlling for anxiety sensitivity, pain avoidance, fear of pain, pain catastrophizing, and sex
A two-step multiple linear regression analysis was used to test the relative contribution of alexithymia in predicting average pain intensity after controlling for sex and some of the factors in Turk's diathesis-stress model of chronic pain and disability.Results of the analyses are presented in Table 2.
First, fear of pain, anxiety sensitivity, pain avoidance, pain catastrophizing, and sex were entered in the regression analysis to create model 1. Results indicated that these five variables together accounted for 27% of the variance in average pain were the only three significant predictors of average pain intensity.Fear of pain and sex accounted for 20.0% and 6.8% of the variance, respectively; alexithymia accounted for an additional 9.6% of unique variance.
Further analyses were conducted to determine which aspects of alexithymia accounted for the observed relationship with average pain intensity.A series of three linear regression analyses were conducted.Each of the three subscales of the TAS-20 -difficulty identifying feelings (factor 1), difficulty describing feelings (factor 2), and externally oriented thinking (factor 3) -was entered in three separate models after controlling for variables in model 1. Results of these analyses are presented in Table 2.For all three models, the overall model predicting average pain intensity was significant (Factor 1: F [6,60]

examining possible interactions among significant predictors of pain intensity
To examine whether fear of pain and alexithymia interacted to predict average pain intensity, a linear regression model was constructed that included the two variables and their interaction (multiplying the two variables after centering).The overall model significantly predicted average pain intensity (F [3,63]=8.44;R 2 =0.29;P<0.001).Fear of pain (β=0.39,t=3.58,P=0.001) and alexithymia (β=0.35,t=3.12,P=0.003) significantly predicted average pain intensity but the fear of pain × alexithymia interaction did not (β=-0.02,t=-0.18,P=0.86), which suggests alexithymia and fear of pain are independent predictors of average pain intensity.

disCussion
The purpose of the present study was to investigate what role, if any, alexithymia plays in predicting pain intensity ratings, relative to fear-and anxiety-based constructs outlined in Turk's diathesis-stress model (24) and commonly assessed in the pain literature.The results indicate pain catastrophizing, anxiety sensitivity, pain avoidance, fear of pain, and alexithymia accounted for 35% of the variance in average heat pain ratings.Fear of pain, sex, and alexithymia were the only significant predictors in the final regression model, accounting for 20.0%, 6.8%, and 9.6% of unique variance, respectively.Follow-up analyses failed to find a significant interaction between fear of pain and alexithymia, or between sex and fear of pain, or sex and alexithymia, indicating that these variables independently predict heat pain ratings.Additional analyses found the difficulty identifying feelings and difficulty describing feelings subscales of the TAS-20 were significant predictors of average heat pain ratings, while the externally oriented thinking subscale was not.The present study is the first to measure both fear of pain and alexithymia in participants undergoing heat pain stimulation.The results are consistent with previous research examining the relationships between pain and fear of pain, and pain and alexithymia.Research has shown a significant positive correlation between alexithymia and pain ratings in healthy subjects during medical procedures (8,49) and in response to experimentally induced pain (7,9).Alexithymia has also been shown to correlate positively with pain severity, after controlling for depressed mood, in patients with painful temporomandibular disorder (50).Research also demonstrates a significant association between the minor pain subscale of the FPQ-III and pain intensity scores during an ischemic pain test, as well as an association between FPQ-III total scores and pain tolerance during electrical stimulation and thermal pain testing (51).High fear of pain, as measured by a Dutch version of the FPQ, has also been associated with increased cold pressor pain ratings (52).
The results of the present study indicate both fear of pain and alexithymia predict pain intensity ratings to thermal stimuli between 46°C and 49°C.Numerous studies have documented a link between alexithymia and over-reporting of physical symptoms (10), as well as physical illness, including chronic pain (50,53,54).Lumley et al (55) suggest individuals with alexithymia may experience physiological hyperarousal and a biased perception and reporting of somatic sensations, leading to increased physical illness.Alexithymia correlates significantly with measures of somatosensory amplification (56,57), lower tolerance to painful electrical stimulation (7), and is associated with higher baseline levels of sympathetic activity (55).In the present study, individuals with higher scores on the TAS-20 may have had a tendency to be excessively aware of or attentive to their bodies, relative to individuals with lower scores, resulting in amplified pain experiences and/or pain ratings in response to the unpleasant thermal stimulation.It is also possible, however, that individuals with higher TAS-20 scores have lower thresholds to painful stimuli reflecting a difference at an earlier phase of sensory processing (eg, at the spinal cord level).Future research may consider using the nociceptive flexion reflex paradigm (58) to help distinguish between these two possibilities.The nonsignificant interactions between sex and fear of pain and sex and alexithymia suggest that the influence of the latter two on pain intensity ratings was not due to a sex effect.
Hypervigilance to bodily sensations may also account for the relationship observed between fear of pain scores and heat pain ratings.Fear-avoidance models of chronic pain suggest that individuals who interpret pain as threatening may experience increased fear of pain, which may, in turn, promote a hypervigilance to body sensations, among other responses such as avoidance and guarding behaviours (39,59).
Interestingly, pain catastrophizing, pain avoidance, and anxiety sensitivity were not significant predictors of heat pain intensity ratings in the present study.One possible explanation for the lack of a significant association between catastrophizing and pain ratings is that catastrophizing, as measured by the PCS, may differ from actual catastrophizing experienced during experimental pain testing.Studies examining the administration of a standardized questionnaire, such as the PCS, and measures of catastrophizing in vivo during pain testing have found only a moderate correlation between in vivo catastrophizing and PCS scores (r=0.46).Moreover, only in vivo catastrophizing, and not PCS scores, correlated with cold pressor pain ratings and pain tolerance (49,60).
The lack of a significant association between pain avoidance and average pain intensity suggests pain avoidance responses, as measured by the PASS-AVO, which was designed to measure avoidance in the context of chronic pain, may not generalize to avoidance behaviours in the context of acute experimental pain.Anxiety sensitivity also did not have a significant direct effect on heat pain ratings.However, this does not rule out the possibility that anxiety sensitivity had an indirect effect on pain ratings through its relationship with alexithymia and/or fear of pain.Anxiety sensitivity has been shown to correlate with higher sensory pain ratings in experimental settings (61)(62)(63), as well as with fear of pain (14,38,(64)(65)(66) and alexithymia (67,68).
It is important to note that the present study had a limited number of participants (n=7) with alexithymia scores in the clinical range.Therefore, caution should be taken in generalizing the present results to individuals with alexithymia.Furthermore, the present study focused on pain-free undergraduate university students; the relationships between alexithymia and the variables in Turk's diathesis-stress model may differ in individuals with chronic pain.Future research exploring the relationships among fear of pain, alexithymia, and pain perception in individuals with clinical levels of alexithymia and/or chronic pain will help further elucidate the relationship among these variables.suMMARy Individuals who fear pain or have difficulty describing and identifying emotions reported greater pain intensity to thermal stimulation.These findings add to the growing body of literature linking alexithymia to pain and suggest that difficulties with emotion regulation, either through reduced emotional awareness via alexithymia or heightened emotional awareness via fear of pain, may negatively impact the pain experience.

ACKnoWLedGeMents:
The present study was supported in part by infrastructure grants from the Canadian Foundation for Innovation and the Ontario Innovation Trust.JK is supported by a Canadian Institutes of Health Research (CIHR) Canada Research Chair in Health Psychology at York University.MGP is supported by a CIHR Canada Graduate Masters Award.ALM is supported by a CIHR Doctoral Award.MGP and ALM are Strategic Training Fellows in Pain: Molecules to Community.