Table 2.

Outcome and Engagement Measures Used.

2020 Studies	Outcome Measures	Engagement Measurement
Fulmer et al. 19	(1) Depression (PHQ-9) (2) Anxiety (GAD-7) (3) Positive and Negative Affect Scale (4) User satisfaction (survey)	(1) Number of messages exchanged between the participant and the conversational agent, Tess, compared to the participant and the e-book
Inkster et al. 20	(1) Self-reported PHQ-9	(1) Engagement effectiveness: User’s in-app feedback responses were performed using thematic analysis (2) Engagement efficacy: Analysis of objections raised by users—conversation messages were tagged for “objection” or “no objection.” Objections were either refusals (user says: “I don’t want to do this” to a bot’s understanding of what was said) or complaints (“That’s not what I said” to a bot’s response)
Jungmann et al. 21	Agreement between main diagnosis of case vignette in textbook and result given by the app	Not specified
Martínez-Miranda et al. 22	(1) Hamilton Depression Rating, using the validated Spanish version (2) Plutchik Suicide Risk Scale, validated Spanish version (3) Hamilton Anxiety Rating Scale, validated Spanish version	(1) Average number of sessions carried by users with ECA (2) Total duration in minutes
Philip et al. 23	(1) 12 Survey questions regarding credibility, benevolence, satisfaction, and usability	(1) Surveyed “are you willing to engage in a new interaction with the virtual agent?” after the interview with the virtual medical assistant to assess future engagement
Provoost et al. 24	(1) Agreement between algorithm and human judgment	Not specified
Suganuma et al. 25	(1) WHO-5 score (2) Kessler 10 score (3) BADS	Not specified

Note. WHO = World Health Organization; GAD-7 = General Anxiety Disorder-7; BADS = Behavioral Activation for Depression Scale; PHQ-9 = Patient Health Questionnaire-9; ECA = embodied conversational agent (chatbot).