Psychological flexibility in migraine: A study of pain acceptance and values-based action

Introduction

Migraine affects 12% of the population yearly (1) and is the third most common medical condition worldwide (2), resulting in substantial personal disability (1–3). A growing literature attests to the role of psychological factors in migraine. Psychiatric disorders such as major depression and anxiety disorders are commonly comorbid with migraine, and these conditions compound the negative impact of migraine; their presence is associated with a poorer treatment prognosis, increased disability, and lower satisfaction with medical care (3–5).

Most recently, interest in psychological factors relevant to headache has expanded beyond discrete disorders and into dimensional constructs such as fear of pain, maladaptive coping, and avoidance of headache triggers (6–8). These manifestations of experiential avoidance reflect an inability or unwillingness to experience aversive private experiences (e.g. bodily sensations, thoughts, emotions) (9). In chronic pain, avoidance is motivated by fear of pain and of pain-related impairment. Although effective in reducing immediate discomfort and accompanying negative affect, avoidance that is prolonged or unwarranted can foster hypersensitivity to pain stimuli, physical deconditioning, and social isolation (8,10). Acute pain paradigms link avoidance with reduced pain tolerance and poor coping (11,12), and clinic studies with chronic pain patients confirm that avoidance is negatively associated with successful adjustment to pain, independent of pain severity (13,14).

In contrast to the maladaptive response of avoidance, “psychological flexibility” denotes a willingness to experience internal events as they occur (acceptance) and engage in behaviors to achieve larger goals and values (values-based action), even in the presence of pain (14). Therapeutic interventions designed to foster psychological flexibility, principally acceptance and commitment therapy (ACT) (9), endeavor to improve functioning more than to reduce symptoms. These interventions have a rapidly-growing body of evidence for efficacy with patients with recurrent medical conditions such as diabetes (15) and epilepsy (16).

The efficacy of interventions fostering acceptance of pain and values-based action is particularly well-established in chronic pain, such that the American Psychological Association designated ACT as having “strong research support” for chronic pain based on results from numerous randomized controlled trials (17,18). Although most studies have focused on heterogeneous pain samples, recently these interventions have been evaluated in two small studies of chronic headache. In both, interventions emphasizing pain acceptance and values-based action yielded significant reductions in headache-related disability and affective symptoms compared to usual treatment (19,20). Despite these promising findings, the underlying constructs targeted by these interventions merit study among migraine sufferers. The purpose of the present study thus was to examine the roles of acceptance of pain and values-based action in migraine patients. We hypothesized that pain acceptance and values-based action would be inversely associated with migraine severity, frequency, and disability, even after controlling for relevant demographic variables and headache pain itself. A secondary aim was to explore relations between fear of pain and psychological flexibility.

Methods

Results

Regression models

Pain severity, pain frequency, and pain-related medical visits

Results from the hierarchical regression analyses are presented in Table 1. In the first regression, with migraine severity as the criterion variable, the addition of the measures of psychological flexibility in the second block accounted for an additional 10% of unique variance (p =  0.006). Examination of the squared semipartial correlations indicated that CPVI scores contributed 8% of the unique variance (p = 0.004), while CPAQ scores contributed less than 1%. The addition of psychological flexibility scores to the regressions using migraine frequency and number of pain-related medical visits (in the past six months) as criterion variables did not provide a statistically significant change in R².

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Table 1.

Hierarchical multiple regression analyses of psychological flexibility variables in relation to headache-related functioning.

Block (step) predictor	B	95% CI for B	p value	ΔR2 of block	Semi-partial correlation	Total R2
Headache severity
1. Gender	1.57	0.49, 2.63	0.005	0.08
2. CPAQ	−0.00	−0.03, 0.02	0.69	0.10	−0.04	0.18
CPVI	−0.51	−0.85, –0.17	<0.01		−0.28
Headache frequency
1. Headache severity	−1.06	−3.91, 1.79	0.46	0.03
Gender	−9.66	−25.86, 6.58	0.24
2. CPAQ	0.13	−0.17, 0.43	0.40	0.05	0.09	0.08
CPVI	−5.95	−11.16, –0.74	0.03		−0.23
Pain-related medical visits
1. Headache severity	0.51	0.05, 0.97	0.03	0.05
Gender	−0.87	−3.37, 1.63	0.49
2. CPAQ	0.01	−0.04, 0.06	0.76	0.04	0.03	0.09
CPVI	−0.84	−1.68, 0.00	0.05		−0.20
Disability: MIDAS
1. Headache severity	8.14	3.30, 12.97	<0.01	0.11
Gender	−6.98	−33.49, 9.53	0.60
2. CPAQ	−0.52	−0.96,−0.06	0.03	0.20	−0.19	0.30
CPVI	−14.83	−22.86,−6.81	<0.001		−0.32
Disability: HIT-6
1. Severity	1.80	1.18, 2.41	<0.001	0.28
Gender	0.12	−3.27, 3.51	0.95
2. CPAQ	−0.04	−0.11, 0.02	0.19	0.06	−0.11	0.34
CPVI	−1.15	−2.27, −0.04	0.04		−0.17

Bolded ΔR² values indicate statistically significant proportion of unique variance accounted for by Block 2 (after controlling for variables in Step 1). CI: confidence interval; CPAQ: Chronic Pain Acceptance Questionnaire; CPVI: Chronic Pain Values Inventory; MIDAS: Migraine Disability Assessment Scale; HIT-6: Headache Impact Test-6.

Headache-related disability

In the first disability regression, MIDAS scores served as the criterion variable. The addition of psychological flexibility scores provided a unique increase in R² of 20% (p < 0.001), indicating that together the CPVI and CPAQ scores contributed substantially and uniquely to MIDAS scores. As with the relative contributions of the headache severity regression, CPVI scores accounted for considerably more variance than CPAQ scores (10.18 vs. 3.76%). In the second disability analysis using the HIT-6, psychological flexibility provided a significant but smaller change in R² of 0.06 (p = 0.020). CPVI scores contributed a significant 3% of the variance in HIT-6 scores when other variables were held constant, while CPAQ scores contributed only 1.3%.

Discussion

The current study evaluated the constructs of pain acceptance and values-based action, two components of psychological flexibility, in the context of headache-related outcomes among treatment-seeking migraineurs. Consistent with prior findings from musculoskeletal pain studies (14,17,24), psychological flexibility was associated with improved patient functioning independent of headache severity and gender differences.

Inverse relationships were found between the measures of psychological flexibility and migraine severity, disability, and pain-related anxiety, such that greater acceptance of pain and engagement in valued activities was associated with lower impact of headache. Psychological flexibility was most strongly associated with migraine-related disability, showing a medium-to-large effect on MIDAS scores (20% of variance) after controlling for pain severity and gender differences. Sensitivity analyses confirmed that this effect was not attributable to general psychological distress. Notably, pain acceptance and values-based action accounted for more variance in MIDAS scores after controlling for covariates than did headache frequency or severity before any covariate adjustments (19% and 11%, respectively). These findings further underscore the importance of avoidance (low psychological flexibility) in headache, particularly in headache-related disability, but do so more broadly than has the fear-avoidance model of pain (10). That is, the psychological flexibility model encompasses broader patterns of experiential avoidance (vs. situational avoidance) and incorporates psychological processes beyond fear of pain specifically (e.g. values-based action, mindfulness) (32). As such, the present findings build on a growing body of literature suggesting that psychological responses to pain may be more disabling than pain itself (13,14,17,33).

Psychological flexibility was uniquely associated with disability also when measured by the HIT-6, though the relationship was not as strong as with the MIDAS, possibly because of differences in response formats of the two disability measures. The MIDAS quantifies days of impairment from headache, while the HIT-6 primarily measures the affective and cognitive impact of headache using a Likert-type scale. We included both measures in light of data suggesting that using both with treatment-seeking headache patients provides a more comprehensive picture of disability than either measure alone (28). Psychological flexibility and headache severity shared a significant inverse relationship. However, psychological flexibility did not exhibit a similar relationship with migraine frequency or number of pain-related medical visits, suggesting that psychological flexibility is most strongly associated with pain perception and impairment. This finding is also consistent with the theoretical tenets of ACT, which prioritizes improvements in functioning above symptom (pain) reduction (9).

Examination of the squared semipartial correlation coefficients showed that the significant effects were driven by values-based behavior more than pain acceptance. The predominant role of values-based action across these three clinic samples underscores that values-based action is not only distinct from pain acceptance (25), but that these two constructs differentially account for unique variance in the domains of disability and quality of life (14,17,23,34). To this end, treatments fostering both pain acceptance and values-based action may hold promise for migraine patients, and the efficacy of these interventions for chronic musculoskeletal pain is already very well established (17,18).

In light of the present findings and empirical challenges to the longstanding clinical advice to avoid headache triggers (8), an alternative approach of promoting psychological flexibility may have far-reaching clinical implications that are yet fully realized in migraine. Two small trials have shown promise for interventions principally targeting psychological flexibility as applied to chronic headache sufferers (19,20), and the present study provides additional impetus for pursuing further research on this construct within migraine specifically.

Strengths of the present study include strong external validity as treatment-seeking patients were recruited both from general practice and neurology clinics across three states, adherence to ICHD diagnostic criteria, and a large sample size dictated by a priori power analysis. Despite the contributions of the current study to understanding the role of psychological flexibility within migraine, limitations exist. First, the cross-sectional design does not lend itself to inferences of causality. Possibly reductions in migraine-related disability increase pain acceptance and values-based action, but that notion is not supported by results from prospective (23) studies and clinical trials (16,19,20). Longitudinal studies and assessment of treatment mediators may further establish temporal relations between psychological flexibility and headache. A second limitation is that the measures of pain acceptance (CPAQ) and values-based action (CPVI) are frequently used in musculoskeletal pain studies but are rather uncommon in headache research. Important differences often manifest between musculoskeletal and headache pain patients, such as differential expectations for improvement and more constant pain vs. episodic attacks characteristic of migraine. No headache-specific measures of pain acceptance or valued action exist, however, and our selection of these measures was informed in part by a recent study suggesting they are viable among headache samples (35). The migraine patients in the present study and the Dindo et al. study (35) obtained similar scores on both the CPAQ and CPVI as musculoskeletal pain patients presenting to primary care settings (14). In conjunction with the included reliability analyses, both measures appear psychometrically sound for further use in headache. As interest in psychological flexibility grows among headache researchers and practitioners, developing headache-specific measures of these and other processes of psychological flexibility may prove useful.

Other valuable future directions include longitudinal studies assessing psychological flexibility processes as potential mediators of long-term headache outcomes and as resilience factors that may reduce one's likelihood of headache progression or chronification. From a treatment perspective, needed are larger trials of ACT for migraine using active control groups and follow-up periods of long duration. To the extent that interventions targeting psychological flexibility prove efficacious and complement established pharmacologic and behavioral migraine interventions, their integration may yield added clinical benefit.

Article highlights

Acceptance of pain and values-based action were strongly associated with headache frequency and disability.