Table 1.

Outcome assessments and assessment time point

Variables	Measurement	Screening	T0	T1	T2	T3
Inclusion/exclusion criteria
Chronic Back pain	MR + TI	x	x
Depressive symptomatology	PHQ-9	x	x	x	x	x
Inclusion criteria a), c), d)	TI/SRQ		x
Acute/past 6 months depressive episode, dysthymia or bipolar disorder	SCID		x			x
Current/past 6 months/on waiting list for psychotherapy	TI		x
Suicidality	SCID/HAM-D/QIDS		x			x
	PHQ-9	x	x	x	x	x
Primary outcome
Onset of Depression	SCID		x			x
Secondary outcomes
Severity of depressive symptoms	PHQ-9	x	x	x	x	x
	HAM-D/QIDS		x			x
Quality of life	AQOL-6D/EQ-5D-5 L		x	x	x	x
Pain intensity	Rating scale		x	x	x	x
Pain related disability	ODI		x	x	x	x
Pain self-efficacy	PSEQ		x	x	x	x
Ability to work	SPE		x	x	x	x
Economic evaluation
Costs	TiC-P		x		x	x
Quality of life	AQOL-6D/EQ-5D-5 L		x	x	x	x
Covariates
Demographic variables	SRQ/MR	x	x
Depression type and chronicity	SCID		x			x
Patient adherence	Attrition rate			x	x
Patient satisfaction	CSQ-8a			x
Side-effects of intervention	INEPa			x	x
Back Pain type and chronicity	MR	x
Internet affinity	IAS		x

AQol-6D Assessment of Quality of Life, CSQ-8 Client Satisfaction Questionnaire, EQ-5D-5 L European Quality of Life scale, HAM-D Hamilton Rating Scale for Depression, IAS Internet Affinity Scale, INEP Inventory for the Assessment of Negative Effects of Psychotherapy, MR Medical record, ODI Oswestry Disability Index, PHQ-9 Patient Health Questionnaire, PSEQ Pain Self-Efficacy Questionnaire, SCID Structured Clinical Interview for DSM, SPE Subjective Prognostic Employment scale, SRQ Self-report assessment questionnaire, TI telephone interview, TiC-P Trimbos/iMTA questionnaire for costs associated with psychiatric illness

^aintervention group only