Discussion
chronic headache disorders, pain, headache-related disability, headache, migraine
MIGRAINE, CHRONIC PAIN, SECONDARY, HEADACHE DISORDERS
There was no indication that the CHESS intervention had any important beneficial effects on clinically relevant outcomes. Only at 4 months was there an indication, on balance, that there was beneficial effect on the HIT-6, −1.0 (95% CI −1.91 to −0.006); In our secondary outcomes, only for pain self-efficacy was there a benefit from treatment, observed at 4 and 12 months but not at 8 months. This may just be a chance finding because of multiple comparisons. However, it might indicate that our intervention does improve self-efficacy, one of our key intervention targets, but that this does not translate into a measured patient benefit.During trial design, the most appropriate measure for a population that may not have been given a headache diagnosis was the HIT-6.A quarter of people in the intervention group did not attend any treatment sessions. This was despite participants confirming they were available on proposed dates before randomization. Nonattendance is common in trials of group interventions for chronic pain, for example, 17% and 11% in 2 similar studies.Although diaries were poorly completed, the findings were consistent with main results. Defining the population of interest is important for trials of interventions of headache disorders. It is also important that criteria developed for evaluating drug treatments for pain are not inappropriately applied to studies on nonpharmacological treatments.The CHESS intervention in the absence of a clinical effect seems to generate additional QALYs and has a high probability of cost-effectiveness given UK cost-effectiveness thresholds. The EQ-5D-5L might be measuring nonspecific effects not captured by the HIT-6 or it might be that the early effect on headache-related disability has had a larger proportional effect in the area under the curve analysis.The control intervention was more than just usual care; the results of the classification interview were fed back to participants and their GPs, which might have reduced any potential effect size from the CHESS intervention if people in the control group used medication more appropriately in light of our feedback. However, the absence of any differences over time in either group in the use of prophylactic medications make it unlikely that improved diagnosis in the control group affected our findings.The trial found no evidence of any clinically relevant benefit from the CHESS intervention across multiple outcomes, at multiple time points, or in any sensitivity or subgroup analyses. It clearly demonstrates the intervention tested here is ineffective and not detrimental. This is surprising because the CHESS intervention targeted the key modifiable psychological variables known to be predictive of poor prognosis in chronic headache disorders, had a solid theoretical underpinning, intervention fidelity was high, and it was well regarded by participants and facilitators.In conclusion, our data effectively exclude the possibility that this short intervention is effective for the treatment of chronic migraine or chronic tension–type headache and episodic migraine. There remains a need to identify more effective treatments for people living with, the sometimes disabling, symptoms of chronic migraine or chronic tension–type headache and episodic migraine.