Table 1.
Key variables and measurements
| Variables | Measurement | Depression screenings (PHQ-9) | T0 | T1 | T2 | ||
| 1 | 2 | 3 | |||||
| Inclusion/exclusion criteria | |||||||
| Chronic back pain | MR+TI | x | x | ||||
| Mild-to-moderate depression or dysthymia | PHQ-9/HAM-D/QIDS/SCID | x | x | x | |||
| Severe depression (ICD-10 F32.2/F32.3/F33.2/F33.3 diagnosis) | SCID | x | x | x | |||
| Suicidality | HAM-D/QIDS/SCID | x | x | x | |||
| PHQ-9 | x | x | x | x | x | x | |
| Further inclusion and exclusion criteria 1, 4, 5 and 6 | SRQ+TI | x | x | ||||
| Primary outcome | |||||||
| Depression severity | HAM-D | x | x | x | |||
| Secondary outcomes | |||||||
| Depression remission and response | HAM-D/SCID/QIDS | x | x | x | |||
| Quality of life | AQol-6D/EQ-5D-5L | x | x | x | |||
| Pain intensity | Numerical rating scale | x | x | x | |||
| Pain-related disability | ODI | x | x | x | |||
| Pain self-efficacy | PSEQ | x | x | x | |||
| Work capacity | SPE | x | x | x | |||
| Measurements for the economic evaluation | |||||||
| Costs | TiC-P | x | x | ||||
| Quality of life | AQol-6D/EQ-5D-5L | x | x | x | |||
| Covariates | |||||||
| Demographic variables | SRQ/MR | x | x | ||||
| Depression type and chronicity | SCID | x | x | x | |||
| Prior depression treatment | TI | x | x | ||||
| Back pain type and chronicity | MR | x | x | ||||
| Internet affinity | IAS | x | x | ||||
| Patient adherence* | Attrition rate | x | x | ||||
| Patient satisfaction* | CSQ-8 | x | |||||
| Negative effects of the intervention | INEP/SRQ/TI/SReC | x | |||||
*Intervention group only.
AQol-6D, Assessment of Quality of Life; CSQ-8, Client Satisfaction Questionnaire; EQ-5D-5L, European Quality of Life scale; HAM-D, Hamilton Rating Scale for Depression; IAS, Internet Affinity Scale; ICD-10, 10th revision of the International Statistical Classification of Diseases and Related Health Problems; INEP, Inventory for the Assessment of Negative Effects of Psychotherapy; MR, medical record; ODI, Oswestry Disability Index; PHQ-9, Patient Health Questionnaire-9; PSEQ, Pain Self-Efficacy Questionnaire; QIDS, Quick Inventory of Depressive Symptomatology; SCID, Structured Clinical Interview; SPE, Subjective Prognostic Employment Scale; SReC, self-report during treatment to the eCoach; SRQ, Self-Report Assessment Questionnaire, TI, telephone interview; TiC-P, Trimbos/iMTA questionnaire for costs associated with psychiatric illness.