The Role of Fear of Pain in Headache
The Role of Fear of Pain in Headache
The FA model, originally developed to explain the transition from acute to chronic pain, has been researched primarily with chronic musculoskeletal pain patients. With a scarcity of research in headache samples, the present study sought to examine the role of pain-related fear in primary headache disorders. As hypothesized, headache sufferers reported greater FOP than non-headache controls, consistent with results from previous cross-sectional studies indicating greater fear of severe and medical pain and cognitive anxiety among headache sufferers than those without headache. Notably, however, non-headache controls differed significantly from migraineurs, but not individuals with TTH, on reported levels of pain-related fear. This finding may be a function of the higher pain severity characteristic of migraine vs TTH, as prior studies from the chronic musculoskeletal pain literature have shown positive associations between pain severity and FOP.
In addition to differences in pain severity, migraine and TTH are associated with differing levels of disability and avoidance behavior, both of which are influenced by FOP and pain chronicity. We thus endeavored to compare FOP also across specific headache diagnoses. As hypothesized, migraineurs reported greater FOP than TTH sufferers, with chronic migraineurs reporting higher FOP than episodic migraineurs. These findings are consistent with the chronic pain literature, indicating that avoidance is related more strongly to chronicity than to pain intensity.
The present study also highlighted the utility of FOP in predicting headache-related variables. Given that headache is among the top 10 most disabling medical conditions worldwide, perhaps the most striking finding was the proportion of variance in disability accounted for by FOP (17.5%), exceeding that accounted for by gender, anxiety, and depression combined (13.8%). Even after controlling for these covariates, FOP remained a strong unique predictor of headache disability, and this relationship approximated a medium effect size. This result parallels findings within a predominantly treatment-seeking headache sample from Nash et al, in which FOP (specifically physiological anxiety) accounted for 14% of variance in disability after controlling for pain, emotional distress, self-efficacy, and locus of control. Considered in conjunction, these findings suggest that existing FA models of pain are relevant not only to chronic musculoskeletal pain, but to headache as well.
Because prior headache studies on FOP have not examined pain-related variables beyond disability, we also assessed its relation to headache severity and frequency, given their established contributions to avoidance behaviors and disability. Increases in FOP were associated with more frequent and more painful headache, which further account for the aforementioned differences across headache diagnostic groups. These findings replicate those from musculoskeletal pain studies showing similar positive associations between FOP measures and measures of severity or disability. In applying the FA model to headache, heightened FOP promotes escape and avoidance behaviors such as avoiding potential headache triggers or situations putatively associated with headache, which can compound pain-related disability by preventing fear extinction, fostering sensitivity to headache triggers, and contributing to social withdrawal. Indeed, a series of experimental studies on exposure to headache triggers suggests that avoidance of triggers may actually sensitize headache sufferers to these triggers over time. In conjunction with the present results, there is a need for increased attention to constructs such as FOP and avoidance in headache disorders, insofar as the traditional clinical advice to merely avoid potential headache triggers, in some cases, may not be a sufficient treatment strategy and may perpetuate headache over time.
As hypothesized, headache severity and headache-related disability were positively associated, indicating the presence of an effect to be mediated. The mediation analysis showed that this association was partially driven by FOP, consistent with findings in chronic back pain. Individuals with higher FOP were more disabled by headache than those with lower FOP scores, even when pain severity was held constant. Pain severity thus influences FOP, which in turn affects disability. Despite the finding that FOP was a statistically significant mediator, the clinical significance of the mediation effect was somewhat modest. Although only 6% of the variance in FOP was explained by headache severity, similar to the findings of French and colleagues, 45% of the variance in headache disability was accounted for by both FOP and headache severity. A substantial amount of unexplained variance in disability remained, however, perhaps because our sample consisted of non-treatment seeking headache sufferers or because other potential mediators were not evaluated. For instance, both coping strategies and perceived self-efficacy influence adjustment to pain but were not a focus of the present study. Given its importance in pain-related functioning, future studies should explore the relationship between FOP and headache self-efficacy to determine how these psychological constructs may influence coping strategies.
Understanding associations between FOP and headache may have significant therapeutic implications, as early detection of FOP may reduce the likelihood of headache chronification and disability, particularly if FOP can be targeted therapeutically before becoming severe. In the chronic pain literature, cognitive-behavioral therapies have shown efficacy in reducing pain-related fear, thereby decreasing disability and improving overall functioning. Specifically, in vivo graded exposure to feared pain stimuli (eg, movement) is effective in reducing FOP and disability in chronic lower back pain patients, but studies on headache patients are lacking. Given the observed role of FOP in headache, behavioral interventions targeting this fear may improve functional improvement in this population, particularly if the present results are confirmed in clinical samples. However, most existing behavioral headache therapies aim primarily to reduce headache frequency by teaching skills of managing headache stressors/triggers and controlling physiological responses rather than altering FOP per se. An increased focus on headache-related disability as a primary outcome could kindle interest in addressing constructs such as FOP in treatment, as well as attempts to integrate exposure-based treatments of this fear into well-established behavioral headache therapies.
Strengths of the current study include a large sample size, a strong statistical methodology, and utilization of a well-validated measure of headache-related disability. However, caution is advised when drawing generalizations from the current study, as limitations exist. Results may have limited generalizability to older adults and clinical settings. However, young adult headache sufferers are a desirable population for investigating potential mediator variables in headache, given their absence of years of medication overuse and headache chronification that can confound the study of mediator variables among treatment-seeking patients. Notably, a substantial proportion of these non-treatment-seeking participants reported being significantly impaired by their headaches as evidenced by interference in everyday responsibilities at home, work, school, and social activities. A second limitation is that the present study was cross-sectional and thus the observed associations should not be interpreted as causal. Although it was assumed that increases in FOP lead to increases in headache-related disability, increases in disability could instead lead to increases in fear, or both may be influenced by a third variable. Mediator analyses by definition involve assumptions about temporal ordering of variables, which in the present study were based on the sequential ordering of these variables in the well-established FA model and previous research showing that FOP predicts pain-related disability. Future studies that experimentally manipulate FOP are needed in order to assess the role of FOP in fostering pain-related attentional biases and escape/avoidance behaviors. Further research is needed also to examine other potential psychological mediators of the headache–disability relationship, such as locus of control and self-efficacy. The need for these studies is underscored by results from the present endeavor, indicating that FOP plays a significant role in primary headache, particularly headache-related disability.
Discussion
The FA model, originally developed to explain the transition from acute to chronic pain, has been researched primarily with chronic musculoskeletal pain patients. With a scarcity of research in headache samples, the present study sought to examine the role of pain-related fear in primary headache disorders. As hypothesized, headache sufferers reported greater FOP than non-headache controls, consistent with results from previous cross-sectional studies indicating greater fear of severe and medical pain and cognitive anxiety among headache sufferers than those without headache. Notably, however, non-headache controls differed significantly from migraineurs, but not individuals with TTH, on reported levels of pain-related fear. This finding may be a function of the higher pain severity characteristic of migraine vs TTH, as prior studies from the chronic musculoskeletal pain literature have shown positive associations between pain severity and FOP.
In addition to differences in pain severity, migraine and TTH are associated with differing levels of disability and avoidance behavior, both of which are influenced by FOP and pain chronicity. We thus endeavored to compare FOP also across specific headache diagnoses. As hypothesized, migraineurs reported greater FOP than TTH sufferers, with chronic migraineurs reporting higher FOP than episodic migraineurs. These findings are consistent with the chronic pain literature, indicating that avoidance is related more strongly to chronicity than to pain intensity.
The present study also highlighted the utility of FOP in predicting headache-related variables. Given that headache is among the top 10 most disabling medical conditions worldwide, perhaps the most striking finding was the proportion of variance in disability accounted for by FOP (17.5%), exceeding that accounted for by gender, anxiety, and depression combined (13.8%). Even after controlling for these covariates, FOP remained a strong unique predictor of headache disability, and this relationship approximated a medium effect size. This result parallels findings within a predominantly treatment-seeking headache sample from Nash et al, in which FOP (specifically physiological anxiety) accounted for 14% of variance in disability after controlling for pain, emotional distress, self-efficacy, and locus of control. Considered in conjunction, these findings suggest that existing FA models of pain are relevant not only to chronic musculoskeletal pain, but to headache as well.
Because prior headache studies on FOP have not examined pain-related variables beyond disability, we also assessed its relation to headache severity and frequency, given their established contributions to avoidance behaviors and disability. Increases in FOP were associated with more frequent and more painful headache, which further account for the aforementioned differences across headache diagnostic groups. These findings replicate those from musculoskeletal pain studies showing similar positive associations between FOP measures and measures of severity or disability. In applying the FA model to headache, heightened FOP promotes escape and avoidance behaviors such as avoiding potential headache triggers or situations putatively associated with headache, which can compound pain-related disability by preventing fear extinction, fostering sensitivity to headache triggers, and contributing to social withdrawal. Indeed, a series of experimental studies on exposure to headache triggers suggests that avoidance of triggers may actually sensitize headache sufferers to these triggers over time. In conjunction with the present results, there is a need for increased attention to constructs such as FOP and avoidance in headache disorders, insofar as the traditional clinical advice to merely avoid potential headache triggers, in some cases, may not be a sufficient treatment strategy and may perpetuate headache over time.
As hypothesized, headache severity and headache-related disability were positively associated, indicating the presence of an effect to be mediated. The mediation analysis showed that this association was partially driven by FOP, consistent with findings in chronic back pain. Individuals with higher FOP were more disabled by headache than those with lower FOP scores, even when pain severity was held constant. Pain severity thus influences FOP, which in turn affects disability. Despite the finding that FOP was a statistically significant mediator, the clinical significance of the mediation effect was somewhat modest. Although only 6% of the variance in FOP was explained by headache severity, similar to the findings of French and colleagues, 45% of the variance in headache disability was accounted for by both FOP and headache severity. A substantial amount of unexplained variance in disability remained, however, perhaps because our sample consisted of non-treatment seeking headache sufferers or because other potential mediators were not evaluated. For instance, both coping strategies and perceived self-efficacy influence adjustment to pain but were not a focus of the present study. Given its importance in pain-related functioning, future studies should explore the relationship between FOP and headache self-efficacy to determine how these psychological constructs may influence coping strategies.
Understanding associations between FOP and headache may have significant therapeutic implications, as early detection of FOP may reduce the likelihood of headache chronification and disability, particularly if FOP can be targeted therapeutically before becoming severe. In the chronic pain literature, cognitive-behavioral therapies have shown efficacy in reducing pain-related fear, thereby decreasing disability and improving overall functioning. Specifically, in vivo graded exposure to feared pain stimuli (eg, movement) is effective in reducing FOP and disability in chronic lower back pain patients, but studies on headache patients are lacking. Given the observed role of FOP in headache, behavioral interventions targeting this fear may improve functional improvement in this population, particularly if the present results are confirmed in clinical samples. However, most existing behavioral headache therapies aim primarily to reduce headache frequency by teaching skills of managing headache stressors/triggers and controlling physiological responses rather than altering FOP per se. An increased focus on headache-related disability as a primary outcome could kindle interest in addressing constructs such as FOP in treatment, as well as attempts to integrate exposure-based treatments of this fear into well-established behavioral headache therapies.
Strengths of the current study include a large sample size, a strong statistical methodology, and utilization of a well-validated measure of headache-related disability. However, caution is advised when drawing generalizations from the current study, as limitations exist. Results may have limited generalizability to older adults and clinical settings. However, young adult headache sufferers are a desirable population for investigating potential mediator variables in headache, given their absence of years of medication overuse and headache chronification that can confound the study of mediator variables among treatment-seeking patients. Notably, a substantial proportion of these non-treatment-seeking participants reported being significantly impaired by their headaches as evidenced by interference in everyday responsibilities at home, work, school, and social activities. A second limitation is that the present study was cross-sectional and thus the observed associations should not be interpreted as causal. Although it was assumed that increases in FOP lead to increases in headache-related disability, increases in disability could instead lead to increases in fear, or both may be influenced by a third variable. Mediator analyses by definition involve assumptions about temporal ordering of variables, which in the present study were based on the sequential ordering of these variables in the well-established FA model and previous research showing that FOP predicts pain-related disability. Future studies that experimentally manipulate FOP are needed in order to assess the role of FOP in fostering pain-related attentional biases and escape/avoidance behaviors. Further research is needed also to examine other potential psychological mediators of the headache–disability relationship, such as locus of control and self-efficacy. The need for these studies is underscored by results from the present endeavor, indicating that FOP plays a significant role in primary headache, particularly headache-related disability.
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