Psychological mediators related to clinical outcome in cognitive behavioural therapy for coronary heart disease: A sub-analysis from the SUPRIM trial

Background The Secondary Prevention in Uppsala Primary Healthcare Project (SUPRIM) was a randomized controlled trial of a group-based cognitive behavioural therapy stress management programme for patients with coronary heart disease. The project was successful in reducing the risk of fatal or non-fatal first recurrent cardiovascular events. The aim of this study was to analyse the effect of cognitive behavioural therapy on self-rated stress, somatic anxiety, vital exhaustion and depression and to study the associations of these factors with the reduction in cardiovascular events. Methods A total of 362 patients were randomly assigned to intervention or usual care groups. The psychological outcomes were assessed five times during 24 months and analysed using linear mixed models. The mediating roles of the outcomes were analysed using joint modelling of the longitudinal and time to event data. Results The intervention had a positive effect on somatic anxiety ( p < 0.05), reflecting a beneficial development over time compared with the controls. Stress, vital exhaustion and depression did not differ between the groups over time. Mediator analysis suggested that somatic anxiety may have mediated the effect of treatment on cardiovascular events. Conclusions The intervention had a small positive effect on somatic anxiety, but did not affect stress, vital exhaustion or depression in patients with coronary heart disease. Somatic anxiety was associated with an increased risk of cardiovascular events and might act as a partial mediator in the treatment effect on cardiovascular events. However, the mechanisms between the intervention and the protective cardiovascular outcome remain to be identified.