Table 2.

Instruments used in the Healthy Teens @ School trial and measurement time points.

Instrument	Abbrev.	Aim/domain	Purpose	Measurement time points
				T1	TM	T2	T3	T4
Intuitive eating scale – 2 (Tylka and Kroon Van Diest, 2013)	IES-2	Intuitive eating	PO	x		x	x	x
Eating disorders examination-questionnaire (Hilbert et al., 2007)	EDE-Q	Eating disorder symptomatology	SCR, SO	x		x	x	x
Weight concerns scale (Killen et al., 1994) - females Male body image concerns scale – males (Weisman et al., 2014)	WCS MBICS	Body image	SO	x		x	x	x
Body mass index	BMI	Weight status	SCR, SO	x		x	x	x
Child depression inventory (Kovacs, 2004)	CDI	Depression	SO, MOD	x	x	x	x	x
State & trait anxiety inventory (Spielberger, 2010)	STAI	Trait anxiety	MOD, MED, SO	x	x	x	x	x
Food frequency questionnaire (adapted from Truthmann et al., 2011)	FFQ	Fruit and vegetable consumption	SO	x		x	x	x
international physical activity scale – adolescents (Hagströmer et al., 2008)	IPAQ-A	Physical activity, sedentary activities	SO	x		x	x	x
KIDCOPE (Spirito et al., 1988)	KIDCOPE	Stress coping	SO	x		x
Credibility & expectancy questionnaire (adapted for online interventions from Devilly and Borkovec, 2000)a	CEQ	Participants expectancy and motivation	MOD, SO	x
Rosenberg self-esteem scale (Rosenberg, 1965)	RSE	Self-esteem	MOD, MED, SO	x	x	x	x	x
Alcohol use test (Bohn et al., 1995)	AUDIT-C	Alcohol consumption/misuse	MOD, MED, SO	x	x	x	x	x
Inventory of life quality in children and adolescents (Mattejat and Remschmidt, 2006)	ILC	Health-related quality of life	SO	x		x	x	x
Working alliance inventory SR (adapted)a (Hatcher and Gillaspy, 2006)	WAI-SR	Satisfaction with treatment	MED		x
Client satisfaction questionnaire (adapted for online interventions from Attkisson and Greenfield, 2004)	CSQ	Satisfaction with treatment	SO			x
Client service receipt inventory (Beecham and Knapp, 2001)	CSRI	Economic evaluation	ECO	x		x	x	x
Platform meta-data		Adherence and engagement	MOD, MED		+
Sociodemographic information		Sex, age, level of education, migration background, household size, relationship status, place of residence, school type, school grade, diagnosed mental disorders and treatments	MOD	x

Abbreviations: PO = primary outcome, SO = secondary outcome, SCR = screening for eating disorders, MOD = moderator, MED = mediator, ECO = economic evaluation; + assessed automatically on the platform during the whole intervention phase; T₁ = baseline, T_M = Mid Intervention, T₂ = post-intervention, T₃ = follow-up 6 months, T₄ = follow-up 12 months.

^aIn intervention group only.