Table 2 Inclusion and Exclusion Criteria

• Research and non-research studies

• Documents addressing adults only or children only

• Documents relevant to any mental health and substance use service setting (i.e., community centers, hospitals, primary care)

• Documents not discussing services for mental or behavioral health or substance use (e.g., focus on physical health services)

• Documents focusing on adolescents, youth, young adults, or emerging adults

• Documents mentioning youth friendliness only in passing/not explaining youth friendliness in ways that answer the research question

• Documents irrespective of gender/sex, and ethnicity

• Documents specific to a particular treatment modality rather than the service setting as a whole (e.g., youth adaptations of cognitive-behavioral therapy)

• Only documents addressing mental/ behavioral health or addiction service settings

• Only documents specifically discussing the definition, characteristics, or expected impact of youth friendliness in these settings

• Conference presentation more than 3 years ago

• Documents originating from developing countries, where youth culture may not be generalizable to that in developed countries