We hypothesized that AS and task-specific anticipatory anxiety would predict laboratory-induced pain responses in a sample of healthy children and adolescents, after controlling for sex, age, and anxiety symptoms. Our hypothesis was partially confirmed in that anticipatory anxiety significantly predicted incremental variance in pain intensity for all three tasks. Anticipatory anxiety accounted for 35-38% of the variance in pain intensity over and above that explained by the other variables, suggesting that it is an important predictor of self-reported pain. Although our models were less successful in explaining tolerance, anticipatory anxiety predicted 10% of additional, unique variance in thermal tolerance, after all other variables were taken into account. Contrary to our hypothesis, AS did not predict incremental variance in pain response. In fact, AS was largely unrelated to pain responses, with the exception of modest correlations with thermal and cold pressor pain intensity (see ). In multivariate analyses, these relationships were no longer significant after controlling for anxious symptomatology.
Our findings are consistent with existing studies reporting positive associations between anticipatory anxiety and procedural pain in children (Hilgard & LeBaron, 1982
; Palermo & Drotar, 1996
). As noted above, we found that anticipatory anxiety showed stronger associations with pain intensity than with pain tolerance. Possible explanations include shared method variance (i.e., use of the VAS for both anxiety and pain ratings) and the notion that anxiety may be linked primarily to pain report, rather than behavioral expression of pain. Previous studies have found discordance between pain intensity and pain tolerance in laboratory studies with younger samples (Fanurik, Zeltzer, Roberts, & Blount, 1993
; Tsao, Fanurik, & Zeltzer, 2003
), suggesting that these response systems are influenced by different factors. In accord, task-based interventions focused on increasing tolerance have led to immediate and long-term improvements in children’s ability to endure pain but without affecting the degree of subjective discomfort (Fanurik et al., 1993
; Tsao et al., 2003
Our null findings for AS agree with Stewart and Pihl (1994)
, who found that AS did not impact pain ratings in response to aversive noise bursts in healthy adult women. However, our findings contradict those of Keogh and colleagues (Keogh & Birkby, 1999
; Keogh & Cochran, 2002
; Keogh & Mansoor, 2001
), who reported that high AS, relative to low AS, was linked with increased pain report in healthy women (but not men). In all but one of these studies, participants were selected based on AS scores, and it may be that the range of responses in our unselected sample did not allow for sufficient differentiation among high and low AS participants. Another possibility is that high AS participants in the Keogh studies who reported increased pain may have simply been responding to the pain in a more anxious way (Keogh & Cochran, 2002
). Nevertheless, it is conceivable that the relationship between AS and pain response found in adults does not hold in younger samples. It may be that this association in girls emerges only at late stages of pubertal development, at which point their responses would be expected to mirror those of adult women. Our results are more in line with Schmidt and Cook (1999)
, who found that AS is linked to increased pain report via heightened anxiety in response to the cold pressor. These authors suggested that AS may increase vulnerability to experiencing anxiety, which then leads to increased pain (Schmidt & Cook, 1999
). In agreement, we found that AS was significantly related to anticipatory anxiety for the thermal and pressure tasks, although the magnitude of the associations was modest.
Notably, our measure of anxious symptomatology predicted significant variance in pain report for the thermal and cold pressor tasks, after controlling for sex and age. These findings are consistent with reports indicating that pain symptoms are associated with symptoms of anxiety in adult panic disorder patients (Schmidt, Santiago, Trakowski, & Kendren, 2002
), as well as studies showing that high trait anxiety is linked to increased laboratory pain ratings (James & Hardardottir, 2002
). In adult clinical populations, prior investigations have documented high rates of comorbidity between chronic pain and anxiety disorders (Asmundson & Taylor, 1996
). The overlap in these disorders remains understudied in younger populations and warrants further attention.
It is noteworthy that use of experimental pain methods in children has been criticized for ethical concerns regarding the induction of pain in such populations, as well as limited generalizability (McGrath, 1993
). While such ethical concerns are understandable, all of our procedures were approved by multiple IRBs and were piloted to ensure safety/acceptability. Regarding limited external validity, laboratory studies have frequently been used in the adult literature to investigate questions concerning clinical pain (Edens & Gil, 1995
). Their reproducibility allows examination of important determinants of pain response, as well as intervention effects, without confounding variables (e.g., variations in intensity/duration) inherent to clinical and procedural pain. Because the laboratory session is a novel experience for participants, such studies are less influenced by participants’ past history with, and the meanings ascribed to, specific pain stimuli, which have been found to impact children’s pain response to medical procedures (Chen, Zeltzer, Craske, & Katz, 1999
). Finally, laboratory pain response has been shown to predict child/adolescent functional impairment, as indexed by school absences (Tsao, Glover, Bursch, Ifekwunigwe, & Zeltzer, 2002
), suggesting that laboratory pain tasks may have real-world application in helping to identify vulnerable populations. These findings also suggest that laboratory pain studies may assist in identifying vulnerability factors that might contribute to the eventual development of chronic pain, although the utility of laboratory studies in this regard has not yet been tested.
Limitations of our study should be mentioned. As discussed above, the strong association between pain intensity and anticipatory anxiety may be due to the fact that they were both assessed using the VAS. It should also be emphasized that our study does not demonstrate that intervening with anticipatory anxiety actually results in changes in pain ratings. In addition, we did not formally screen for anxiety disorders, so it is not known what portion of the sample may have met criteria for an anxiety disorder. However, all participants were attending school and were not taking psychotropic medications. Although we included age as a control variable in our analyses, there was a broad age range in our sample, and it is conceivable that our findings may have differed in older samples with a more restricted age range. It is possible that the relationship between AS and pain found in adults is evident only in older adolescents and additional studies in this population are warranted. Finally, we did not examine which factors were most predictive of task-specific anticipatory anxiety. Muris et al. (2001)
reported that AS is an important predictor of fear of pain in adolescents. Future studies may address the extent to which AS is uniquely related to pain taskspecific anticipatory anxiety, compared with the more general construct of fear of pain.
One clinical implication of our findings is that interventions designed to target anticipatory anxiety may have beneficial effects on pain responses in children and adolescents. Prior research has shown that hypnosis initiated just prior to medical procedures (Zeltzer & LeBaron, 1982
) achieved reductions in acute pain responses. In an uncontrolled study in our clinic, we found that a combined complementary and alternative medicine treatment package incorporating acupuncture and hypnosis resulted in significant reductions in pain for chronic pain patients aged 6-18 years (Zeltzer et al., 2002
). Anxiety about being penetrated with needles is cited as a common fear among children, and clinicians often hesitate to recommend acupuncture for this reason. However, we found acupuncture to be highly acceptable, following sufficient education and hypnosis to reduce anticipatory anxiety. Thus, anxiety-reduction techniques may be useful for increasing the acceptability of invasive treatment procedures in chronic pediatric pain.
In sum, our findings suggest that in healthy children and adolescents, state-specific anxiety in anticipation of pain is an important predictor of pain report, and in certain cases pain tolerance. Anticipatory anxiety demonstrated a unique relationship to pain response, even after taking into account sex, age, and anxious symptomatology. Contrary to expectation, AS showed only weak associations with laboratory pain reactivity. Thus, a proximal measure of the perceived aversiveness or threat value of pain was more strongly linked to pain response than a distal measure of fear of anxiety symptoms. However, future studies should continue to examine the possible role of AS in pediatric pain given the limitations of the present study, as well as prior evidence of significant associations between AS and laboratory pain response in adults. One possibility is that AS may be a vulnerability factor that predisposes certain high-risk populations to chronic pain syndromes, as has been found for panic disorder (Weems, Hayward, Killen, & Taylor, 2002
). Longitudinal studies are needed to examine this possibility with respect to the development of chronic pain. Increased knowledge of how state and trait factors related to anxiety influence pain response may therefore lead to the development of more effective interventions for pain in children and adolescents.