Table 2

Outcome measures

		Months
	Instrument	0	2	4	6	8	12
Respondent: X=Patient; P=Parent
Primary outcome
Physical health	SF-3656 57	X	X	X	X	X	X
Secondary outcomes
Illness severity	SCL-som58	X	X	X	X	X	X
Illness severity	BDS checklist59	X					X
Symptom interference	LI52	XP			XP	X	XP
Depression and anxiety score	SCL-8-6-458 60–62	X			X	X	X
Mental health	SF-3656 57	X	X	X	X	X	X
Illness worry	Whiteley-763	X	X	X	X	X	X
Perceived stress	PSS64	X					X
Overall impression of change	PGIC65				XP	X	XP
Process measures
Illness perception	BIPQ66	XP	X	X	XP	X	XP
Illness related behaviour	BRIQ67	X	X	X	X	X	X
Psychological flexibility	AFQ-Y853	X	X	X	X	X	X
Psychological flexibility	PIPS-1254	X	X	X	X	X	X
Potential moderators
Family functioning	FAD68	XP					XP
Attachment style	ECR-RS69	X
Negative life events	Negative life events70	X
Physiological measures
HRV	HRV measured with the Vagus device (resting state, standing, slow breathing, valsalva)71	X					X
Hair cortisol	Measurement of hair cortisol in 2 strands of hair closest to the scalp (1–2 cm)	X					X
Inflammatory response	IL-6, TNF-α, high-sensitive CRP, IL-1, neopterin, CD163, HO1, MCP1	X					X
Physical activity	Accelerometer (Actigraph wGT3X-BT) worn for 7 consecutive days72	X					X

AFQ-Y8, Avoidance and Fusion Questionnaire for Youth; BDS, bodily distress syndrome; BIPQ, Brief Illness Perception Questionnaire; BRIQ, Behavioural Responses to Illness Questionnaire; CRP, C reactive protein; ECR-RS, Experience in Close Relationships—Relationship Structure; FAD, Family Assessment Device (general functioning subscale); HO1, heme oxygenase-1; HRV, heart rate variability; IL-6, interleukin 6; LI, Limitation Index (Revised from Pain Interference Index); MCP1, monocyte chemoattractant protein-1; P, parent; PGIC, Patient Global Impression of Change; PIPS-12, Psychological Inflexibility in Pain Scale; PSS, Perceived Stress Scale; SCL-8-6-4, Symptom Checklist Revised-90—depression and anxiety subscales; SCL-som, Symptom Checklist Revised-90—somatisation subscale; SF-36, Short Form Health Survey; TNF-α, tumour necrosis factor-α; X, patient.