Table 2 Study Instruments (see Additional file 1 for further descriptions)

 Cardiac Depression (CDS)

The primary outcome of the study was measured using the Cardiac Depression Scale (CDS) by Hare et al., a disease-specific, 26-item questionnaire used to measure depression in patients with CVDs. CDS scores range from 26 to 182, and items are scored on a seven-point Likert scale from 1 (strongly disagree) to 7 (strongly agree) [60]. The CDS can be used as a continuous measure, where higher scores indicate higher depressive symptoms or as an ordinal indicator of possible depression using cut-off points previously used in literature. In this study, the presence of mild-to-moderate depression was defined as a CDS score of 90–100 and the presence of severe depression as a score >100. Scores below 90 indicated no-to-minimal depression [63].

 Depression, anxiety, stress (DASS-42)

Depression (DASS-depression), anxiety (DASS-anxiety) and stress (DASS-stress) were measured using the Depression Anxiety Stress Scale-42 (DASS-42) by Lovibond & Lovibond, a 42-item questionnaire consisting of three subscales, each containing 14 items scored on a four-point Likert scale ranging from 0 (did not apply to me at all) to 3 (applied to me very much), measuring the extent to which each item was experienced over the past week. The scores are classified as: depression 0–9 (normal), 10–20 (mild-moderate), > 21 (severe-very severe); anxiety 0–7 (normal), 8–14 (mild-moderate), > 15 (severe-very severe); stress 0–14 (normal); 15–25 (mild-moderate), > 26 (severe-very severe) [64].

 Somatic Symptoms (PHQ-15)

The Patient Health Questionnaire (PHQ-15) is a 15-item somatic symptom scale derived from the full Patient-Health-Questionnaire to measure the severity of somatization in patients [65].

 Quality of life (SF-12-PCS; SF-12-MCS)

Quality of life was assessed using the 12-item Short-Form Health Survey (SF-12), which is a generic measure of overall health status. The SF-12 is comprised of two components, the Mental Component Summary (MCS) score and the Physical Component Summary (PCS) score [66].

 Post-traumatic stress disorder (PTSD-PCL-S)

The Post-Traumatic Stress Disorder Checklist (PTSD-PCL-S) is a 17-item scale used to assess PTSD symptoms based on the Diagnostic and Statistical Manual of Mental Disorders (DSM IV) criteria. The PTSD-PCL-S is used to link symptom endorsements to a specific stressful or traumatic event or experience [67].

 Social Support (ESSI)

The ENRICHD (Enhancing Recovery in Coronary Heart) Social Support Instrument (ESSI) is a seven-item scale comprised from the Medical Outcomes Survey (MOS). It assesses four components of social support including emotional, instrumental, informational and appraisal [68, 69].

 Self-esteem (SE)

The Single-Item Self-Esteem Scale is a one-item scale developed as an alternative of the Rosenburg Self-Esteem scale [70].

 Resilience (RS-14)

Resilience Scale (RS-14) is a 14-item questionnaire that assesses individual resilience in a general population [71].