(ii) Baseline health questionnaire All participants were invited to complete a questionnaire to ascertain or validate participants' sex, level of education, ethnicity and health. General health functioning was assessed using the EQ-5D, (http://www.euroqol.org/) a 5-item standardised measure of health outcome. Functional chest pain was determined using the Rose angina questionnaire and angina severity using the Canadian Cardiovascular Society (CCS) classification. Symptoms of depression were assessed using the Patient Health Questionnaire-9 (PHQ-9), which scores each of the nine Diagnostic and Statistical Manual of Mental Disorders (DSM-IV 4th Edition, American Psychiatric Association) criteria for depression in the PRIME-MD (Primary Care Evaluation of Mental Disorders screening questionnaire for depressive symptoms) diagnostic instrument for common mental disorders. Anxiety was assessed using the 7-item Generalized Anxiety Disorder (GAD-7) scale, a self-reported measure for screening and quantifying severity of generalized anxiety disorder.