Table 1.

PICOS framework

Concept	Concept details
Population (P)	Youth (12–25 years, inclusive) experiencing non-acute, emerging, mild-to-moderate mental ill-health symptoms. Therefore, we examined indicated populations and excluded universal and selected prevention populations, as well as all treatment and recovery populations. Studies were also excluded if participants had an existing psychiatric diagnosis. We also included studies whose sample fell outside of 12–25, provided the study’s mean age was within 12–25 years (inclusive)
Intervention (I)	Interventions were youth and young-adult specific, intended for those aged between 12 and 25 years. General adult interventions were excluded. The scope of interventions was mental health. Combination interventions that focus on mental ill-health and alcohol and other drugs (AOD) interventions were also included. Entirely AOD interventions were excluded. Interventions were evidence-based or informed and developed by a mental health expert (clinician, researcher, and/or expert by experience). The intervention duration was brief, defined as intervention length ranging from 1 to 12 sessions and duration ranging from 0 to 12 months. Interventions were standardized and manualized (solely or partially). The intervention was digitally delivered by any digital delivery method (e.g., telehealth, email texts, online chats smartphone applications). Interventions were individually delivered, with dyadic or group-based interventions excluded. Intervention delivery channel could be: 1. Combination delivery (partially guided and partially self-guided) or 2. Entirely guided. Such guided delivery could be synchronous (i.e., live contact) or asynchronous (delayed contact). Guidance could include support from a clinician, researcher, expert by experience, or a mix of experts. Self-guided interventions were excluded. There were no theoretical framework parameters around included interventions
Comparison (C)	To be included in this review, studies contained between group data with comparison group being any of the following: placebo, control, group receiving an equivalent in-person program, or any other varied intervention. Thus, no comparisons were imposed. Within-group studies were also included (i.e., where no comparison group data were included)
Outcome (O)	All studies were required to report on pre-post intervention socioemotional outcomes
Study design (S)	Primary research from published and unpublished sources in the form of experimental and quasi-experimental (i.e., randomized controlled trials, non-randomized controlled trials, before and after studies, and interrupted time-series studies) were included. Case control studies were also included. All included studies needed to report on clinical pre-post mental health program efficacy data related to reducing psychological distress