Element	Inclusion criteria
Participants	Inclusion: •Interventions focused on young people aged 14–24 years either as disclosers or as recipients of self-disclosure. (Interventions themselves may include self-disclosure by other age groups provided that the recipients are within the 14–24-year-old age bracket.) •Disclosers are required to have a current or past experience of depression and/or anxiety based on (a) a clinical diagnosis or formulation made by a mental health professional, (b) elevated symptoms confirmed by a standardized assessment tool, or (c) subjective self-report •In the case of preventive interventions, the recipients of personally disclosed information about anxiety and depression may be young people who have not (yet) experienced either condition Exclusion: •Studies where a majority of participants fall outside the 14–24-year-old age cohort
Interventions	Inclusion: •Interventions employing intentional self-disclosure, defined as revealing personal information about lived experiences of anxiety or depression, with the goal to prevent onset of, treat, manage, or prevent relapse of anxiety and/or depression for the disclosers and/or recipients of such information Exclusion: Studies focused on therapists’ self-disclosure were not included
Study design and context	•For comparative trials, the outcomes of self-disclosure interventions are compared against any other comparator or control (which could include alternative delivery formats for self-disclosure) •Outcomes for uncontrolled pre-post evaluations of self-disclosure interventions •Studies from any geographical location, encompassing any health, community, educational or online setting
Outcomes	For the analysis of potential benefits: •The primary quantitative outcomes of interest are improvements in depression and anxiety, measured by validated symptom-based or diagnostic instruments •We are also interested in qualitative reports of symptomatic/diagnostic and functional improvements (e.g., in interpersonal, occupational, and educational domains) For the analysis of potential harms: •Quantitative outcomes of interest are deteriorations in depression and anxiety, measured by validated symptom-based or diagnostic instruments, and serious adverse events defined according to the original study protocols (where reported) •We are also interested in qualitative reports of negative effects on self (e.g., symptoms, functioning, dependency) or others (e.g., stigma experienced from family, friends, peers, community members) For the analysis of mechanisms: •Quantitative outcomes of interest are assessed mediators of intervention effects on anxiety and depression •We are also interested in qualitative reports of how intervention content and materials are taken up and used by recipients/disclosers in self-disclosure interventions; and accounts of how recipients/disclosers describe the ensuing intervention mechanisms and pathways to beneficial outcomes (and potential harms)