Does pain self-efficacy predict, moderate or mediate outcomes in people with chronic headache; an exploratory analysis of the CHESS trial

Abstract Background Chronic headache disorders are disabling. The CHESS trial studied the effects of a short non-pharmacological intervention of education with self-management support for people affected by migraine and/or tension type headache for at least 15 days per month for at least three months. There were no statistically significant effects on the Headache Impact Test-6 (HIT-6) at 12-months. However, we observed improvement in pain self-efficacy questionnaire (PSEQ) and short-term HIT-6. We explored the impact of the CHESS intervention on PSEQ, and subsequently, on the HIT-6 and chronic headache quality of life questionnaire (CH-QLQ) at four, eighth and 12 months. Methods We included all 736 participants from the CHESS trial. We used simple linear regression models to explore the change of HIT-6 and CH-QLQ with treatment and PSEQ at baseline (predictor analysis), and the interaction between treatment and baseline PSEQ (moderator analysis). We considered the change of PSEQ from baseline to four months as a mediator in the mediation analysis. Results Baseline PSEQ neither predicted nor moderated outcomes. The prediction effect on change of HIT-6 from baseline to 12 months was 0.01 (95% CI, -0.03 to 0.04) and the interaction (moderation) effect was −0.07 (95% CI, -0.15 to 0.002). However, the change of PSEQ from baseline to 4-month mediated the HIT-6 (baseline to 8-, and 12-month) and all components of CH-QLQ (baseline to 8-, and 12-month). The CHESS intervention improved the mediated variable, PSEQ, by 2.34 (95% CI, 0.484 to 4.187) units and this corresponds to an increase of 0.21 (95% CI, 0.03 to 0.45) units in HIT-6 at 12-months. The largest mediated effect was observed on the CH-QLQ Emotional Function, an increase of 1.12 (95% CI, 0.22 to 2.20). Conclusions PSEQ was not an effective predictor of outcome. However, change of short-term PSEQ mediated all outcomes, albeit minimally. Future behavioural therapy for chronic headache may need to consider how to achieve larger, and more sustained increases level of self-efficacy than that achieved within the CHESS trial. Trial registration ISRCTN79708100.