Why does migraine improve during a clinical trial? Further results from a trial of cervical manipulation for migraine.

It is generally accepted that migraine is sensitive to intervention, whether in a treatment situation or in a clinical trial, and a "placebo effect" is often suggested. The influence of a number of non-specific therapeutic ingredients was examined in a recent six-month trial of cervical manipulation for migraine, and results of a 20-month follow-up are reported. During the trial migraine attacks reduced significantly by 28%, and reduced a further 19% up to the follow-up period. The possibility of a trial effect, whereby improvement might stem from circumstances of the trial, was dismissed as an explanation for improvement. There was some evidence to suggest that placebo influences made a slight contribution to improvement, with sex, social class and subjects' optimism about the therapist at the initial treatment being weakly associated with initial improvement. The possibility that improvement levels reflected spontaneous improvement in migraine symptoms is suggested. If this possibility proves valid, clinical trials assessing migraine therapies should be designed so as to consider the natural course of migraine. Degree of improvement at follow-up could be predicted clearly from degree of improvement during the treatment phase and from degree of improvement at the end of the trial. This appears to be important to manipulative therapists who appear to practise without the benefit of valid predictors of response to therapy.

RCT Entities:   Population Interventions Outcomes