Table 1.

Measures to be obtained and proposed target mechanisms adolescents and parents.

Construct and method of operationalization		Measure	Timepoint
			Baseline	6 weeks	3 months
Health beliefs
	1. Stigma	1. Depression Stigma Scale [60]	1, 2, 3	1, 2, 3	N/Aa
	2. Beliefs about antidepressants	2. Resistance to Antidepressant Use Questionnaire, Antidepressant Meanings Scale [61]	1, 2, 3	1, 2, 3	N/A
	3. Beliefs about therapy	3a. Adolescent: Barriers to Adolescents Seeking Help [62,63]; 3b. Parent: Parental Barriers to Help Seeking Scale [64]	1, 2, 3	1, 2, 3	N/A
Mental health knowledge
	1. Depression knowledge	1. Depression Literacy Questionnaire [65]	1, 2	1, 2	N/A
	2. Anxiety knowledge	2. Anxiety Literacy Questionnaire [65]	1, 2	1, 2	N/A
Peer emotional /informational support
	1. Perceived emotional/informational support	1. Emotional/Informational Subscale from the Medical Outcomes Study Social Support Survey [66]	1	1, 2	N/A
	2. Actual/observed emotional/informational support	2. Online coding of peer and moderator comments for types of social support [67]	1	1, 2	N/A
Communication quality
	1. Parent-adolescent communication quality	1. Parent-Adolescent Communication Scale [68]	1	1	N/A
Perceived need for treatment
	1. Perceived need for treatment	1a. Open-ended question about whether adolescent/child needs any mental health service [21]; 1b. the General-Practice Users Perceived-Need Inventory [69]	1a, 1b	1a, 1b	N/A
Proposed main outcome: mental health service use
	1. Intention to seek services	1. General Help Seeking Questionnaire [58]
	2. Receipt of any mental health treatment	2a. Combined measure using Electronic Health Record Chart Review and parent/adolescent self-report [14]; 2b. Actual Help Seeking Questionnaire [58,59]	1	2a, 2b	N/A
Exploratory clinical outcomes
	1. Depressive Symptoms	1. Adolescent: Depressive Symptoms: Patient Health Questionnaire-9 item [47]	1, 2, 3, 5	1, 2, 3, 4a, 4b, 5	4a, 4b
	2. Anxiety Symptoms	2. Adolescent: Anxiety Symptoms: Generalized Anxiety Disorder Scale-7 item [49]	1, 2, 3, 5	1, 2, 3, 4a, 4b, 5	4a, 4b
	3. Functioning	3a. Adolescent: Multidimensional Adolescent Functioning Scale [70]; 3b. Parent: Columbia Impairment Scale-Parent [71]	1, 2, 3, 5	1, 2, 3, 4a, 4b, 5	4a, 4b
	4. Continued mental health service use	4a. Combined measure using Electronic Health Record Chart Review and parent/adolescent self-report [14]; 4b. Actual Help Seeking Questionnaire [58,59]	1, 2, 3, 5	1, 2, 3, 4a, 4b, 5	4a, 4b
	5. Relationship quality	5. Parent-child connectedness [72]
Descriptive covariates
	1. Demographics	1. Age, gender, sexuality (adolescent only), race, ethnicity, education, health insurance (parent only – asked of child), transportation, socioeconomic status	1, 2, 3, 4a, 4b	4b	N/A
	2. Treatment history	2. History of medication/therapy in adolescent [73]	1, 2, 3, 4a, 4b	4b	N/A
	3. Treatment provider recommends	3. Chart review for treatment recommendation	1, 2, 3, 4a, 4b	4b	N/A
	4a. Parental mental health history; 4b. Parental receipt of mental health treatment	4a. Parent: Parental self-report mental health history [14]; 4b. Parent: Actual Help Seeking Questionnaire [58,59]	1, 2, 3, 4a, 4b	4b	N/A

^aN/A: not applicable.