Table 1.

Overview of study measures

Variable	Domain	Instrument	Items	Source			Assessment
				Y	P	T	T0	T1	T2	T3	T4	T5
Primary outcomes	Psychological flexibility	AFQ-Y (FV)	17	x			x		x		x	x
		AFQ-Y (SV)	8	x				x		x
	Number of DSM-5 diagnoses	SCID-5 Junior	-	x			x				x	x
Secondary outcomes	Presence of the primary DSM-5 diagnosis	SCID-5 Junior	-	x			x				x	x
	Psychopathology	YSR	69	x			x				x	x
		CBCL	74		x		x				x	x
		BFS	12	x			x	x	x	x	x	x
	Personality problems	SIPP-SF	60	x			x		x		x	x
	Global Functioning	CGAS	1			x	x		x		x
		ORS	4	x			x	x	x	x	x	x
	Individual and societal functioning	ISIQ	10	x			x				x	x
	Quality of life	EuroQol	6	x	x		x		x		x	x
	Stress	PSS (FV)	10	x			x		x		x	x
		PSS (SV)	5	x				x		x
	Treatment satisfaction	SSS	4	x							x
	Drop-out	Drop-out questionnaire	5			x					x
	Therapeutic alliance	TASC	12	x		x		x	x	x	x
Moderators	Demographic characteristics	-	-	x	x	x	x				x	x
	Type of problems	SCID-5 junior	-	x			x				x	x
	Severity of problems	SCID-5 junior	-	x			x				x	x
	Psychopathology of parents/caregivers	ASR	69		x		x				x	x
	Treatment expectancy	PETS	7	x			x
	Previous treatments	VEHI	8	x			x
Mediators	Psychological flexibility	AFQ-Y (FV)	17	x			x		x		x	x
		AFQ-Y (SV)	8	x				x		x
	Emotion regulation	ERSQ	27	x			x		x		x	x
		ERSQ (SV)	9	x				x		x
		FEEL-KJ	30	x			x		x		x	x
	Self-compassion	SCS-SF	12	x			x		x		x	x
	Autonomy	AAQ	18	x			x		x		x	x
	Perfectionism	FMPS	26	x			x		x		x	x
	Self-esteem	RSES	10	x			x		x		x	x
	Group cohesion	GCQ-S	12					x	x	x	x
Other characteristics	Treatment integrity	Observation	-
	Content of TAU	TPC	3			x		x	x	x	x
	Life events	LES	23	x			x				x	x
	Costs	Cost diary	79	x			x				x	x

Abbreviations: FV Full-length version, P Parents/caregivers, SV Short version, T Therapist, T0 Baseline assessment, T1–3 mediator assessments, T4 Post-assessment, T5 6-month follow-up assessment, Y Transitional age youths