Key attributes of integrated community-based youth service hubs for mental health: a scoping review

Background Community-based, integrated youth service hubs have the potential to address some of the longstanding issues with mental health services for youth, including problems with access and system fragmentation. Better understanding of these approaches, particularly efforts to create a single point of entry to comprehensive, evidence-based services through youth service hubs, is needed to help guide future implementation and evaluation. This scoping review identifies the key principles and characteristics of these models of care, as well as the state of the literature, particularly with regard to implementation and replicability. Method Electronic databases and grey literature sources were searched for material from 2001 to 2019, with diverse search terms capturing the concept of “integrated” or “one-stop shop” youth mental health services. Title/abstract and full text review were conducted, as well as additional focused searching. After screening 4891 texts at the title/abstract level and 496 at the full-text level, 110 documents were included for data extraction. Results Several integrated care hub models for youth mental health services and related frameworks were identified internationally, largely in high-income countries. Common principles included an emphasis on rapid access to care and early intervention, youth and family engagement, youth-friendly settings and services, evidence-informed approaches, and partnerships and collaboration. Program characteristics also revealed similarities (e.g., providing evidence-informed or evidence-based services in youth-friendly spaces), with some differences (e.g., care coordination methods, types of service providers), potentially attributable to lack of available information about key ingredients. Outcome research was limited, with few rigorous evaluations of youth outcomes. Moreover, sufficient information for replication, community evaluation of feasibility or actual implementation was rarely provided. Conclusion Internationally, integrated youth service hubs were found to share common key principles, while providing comprehensive services to youth with mental health difficulties. There is a great need for common language and measurement framework to facilitate replication, rigorous evaluation of outcomes, knowledge exchange, and dissemination of findings.


Introduction
Mental health problems commonly start during childhood or adolescence, with about half of all lifetime cases starting by ages 14-15 and three-quarters by ages 18-24 [1,2]. Worldwide, approximately 10-20% of children and adolescents experience mental health disorders [3,4] and cumulative lifetime prevalence approaches 50% among adolescents and young adults in developed countries [1,5,6]. Mental health problems are also associated with high societal burden [7,8]. Despite the clear need for mental health services, youth often do not receive evidence-based services in a timely, effective manner [9,10]. Longstanding problems with youth mental health service provision, including system fragmentation, poor access to evidence-based services, discontinuation of support at the transition to adulthood and lack of an informed developmental perspective, could be effectively addressed by integrated care approaches offered across the adolescent and young adult developmental stages [11,12]. Indeed, models of care that bring traditionally separate services together into one community-based setting to meet youth's unique needs and span the transition to adulthood have recently gained the attention of researchers, service providers, and policymakers [13][14][15].
Integrated community-based youth service hubs (ICYSHs) reflect models of care that provide comprehensive, youth-focused services, including mental health services, health and other community and social services in a single community-based setting, sometimes referred to as "one-stop shops", with "youth" defined to include both adolescents and young adults. Literature reviews of medical and behavioral health integration in primary care settings have been conducted [16,17] and a meta-analysis suggests benefits [18]. However, although ICYSH models are being adopted internationally [13,14], reviews of these integrated community-based models of care are lacking. One recent exception is a 2017 review by Hetrick et al. [19], which describes select programs and their outcome evaluation efforts. Authors highlight the need to further evaluate outcomes and develop best practice models [19]. They do not, however, examine the common principles across various exemplars of ICYSH. In addition, information on implementation of essential features of ICYSH models is needed to ensure that the components most crucial to their success are included in efforts to replicate the model and evaluate the feasibility and outcomes of the model in different contexts. This review identifies ICYSH models for mental health services, their characteristics, common principles, and aspects critical to implementation and replicability.

Search strategy and identification of relevant studies
Scoping review methodology was deemed particularly well-suited to examine the burgeoning area of ICYSHs. Scoping reviews comprehensively identify important concepts in a structured manner [20], including the extent, range, and nature of research activity in areas in which the available range of materials is unknown [21], e.g., when substantial grey literature is expected. The scoping methodology described in the literature was followed [21][22][23]. For a detailed description of the review methodology, see [24]. An electronic search was conducted in Medline, EMBASE, PsycINFO, CINAHL, ASSIA, and Campbell Collaboration Library and Cochrane Library using a combination of subject heading and text word terms for integration AND mental/behavioral health AND children/adolescents. Work published in English between 2001 and 2019 was included to capture recent developments in ICYSH models. Exclusion criteria included comments or notes, editorials, and letters. A total of 4817 unique citations were retrieved from the initial database search, after removing 1166 duplicates (see Fig. 1 for PRISMA diagram).
A grey literature search was undertaken following a comprehensive checklist [25]. A broad Google Advanced Search was performed and a focused search was conducted on specific youth-relevant mental health sites, resulting in 45 grey literature documents. An additional four documents were gathered by reviewing reference lists. The International Journal of Integrated Care was hand searched, yielding seven more articles. Eighteen additional works (eight articles and 10 grey literature documents) known to the authors were included, resulting in 4891 documents screened.
Inclusion criteria were as follows: presenting problem was mental or behavioral health, substance use concerns, or concurrent disorders; population was children, adolescents, youth, emerging adults, or young adults. The United Nations defines "youth" as the age range spanning from 15 to 24 [26]; the age range accepted for inclusion in the review was flexible to accommodate different definitions retained in the literature. Other inclusion criteria included models of care that brought together multiple service components to improve access to service, service quality, client satisfaction, efficiency [27], or youth outcomes [11], and aimed to make mental health systems or service delivery more fulsome [28]; services were coordinated, co-located (multiple types of services beyond mental health, all in a single setting), and community-based (not hospital, primary care, or school based). Non-research literature (e.g., policy documents) was also included to capture a broad range of work.
Titles and abstracts were independently screened by two raters, with project lead consultation to resolve discrepancies. Covidence [29], the Cochrane-recommended systematic review software, was used for title/ abstract and full text review. Reasons for exclusion were: conference presentations presented > 3 years ago; adults or infants only (age < 2); not mental or behavioral health; not linked/integrated services; only hospital consultation-liaison services; only combination therapymedication in a randomized control trial. Following title/ abstract screening, 496 full-text articles were examined; of them, 450 documents were ineligible (see Fig. 1). At this stage, the authors checked references of included studies for other relevant work and conducted a focused search for related documents, adding 64 documents; 110 documents were ultimately included for data extraction. Information was extracted from these documents using a data extraction tool which was iteratively modified based on the knowledge gathered during the scoping review process (see published scoping review protocol for more information [24]). Members of the research team repeatedly read the extracted data, returning to the full text for context, in order to synthesize the findings by consensus. Following extraction, data were reviewed to identify unique programs and examine the extent of information available for each program.

Results
In total, 87 journal articles and 23 grey literature documents were included in the review. The primary purpose of journal articles was: description of ICYSH model, 30 protocol, 1; position papers, 4; review, 1. The diverse grey literature included: government-commissioned reports, reviews and service frameworks, 5; information related to a program model, efforts, and progress, 6; informal program information, 4; in-depth program descriptions/reports, 3; independent program evaluations, 4; model recommendations, 1. In all, 94 documents described components of 8 unique programs (Table 2). Insufficient information to meaningfully review was provided about 11 models, resulting in their exclusion from the detailed analysis in this report, although they are described in summary Table 1.

Summary of models reviewed
Multiple international ICYSH models were identified (  Table 1 for information on all models identified. The Australian headspace model aims to establish a multidisciplinary, primary mental health services model that is highly accessible and specialized to meet the core needs of young people [30,31]. It also aims to bridge mental health service gaps through co-location and common clinical governance. A key principle is that youth are not turned away from services based on severity or diagnosis. headspace seeks to provide early intervention within an enhanced primary care one-stop shop that is closely linked to local specialist services, schools, and other communitybased organizations [14]. As of early 2019, there are a total of 110 headspace centers established in Australia [32]. Orygen Youth Health in Australia evolved out of the Early Psychosis Prevention and Intervention Centre (EPPIC) model [14]. This service seeks to bridge the gap between child/adolescent and adult mental health services in the Melbourne area [33]. Four specialized clinics focus on youth with first episode psychosis, mood disorders, emerging borderline personality disorder, and youth at ultra-high risk for a psychotic disorder [14]. Each clinic provides a full complement of interventions over a 2-year period of care. A youth access team provides triage, assessment, and crisis response 24 h a day, 7 days a week, as well as community and home-based services [14].
Headstrong, the National Centre for Youth Mental Health in Ireland, established Jigsaw [34] to integrate supports and services for young people through community capacity building, with 13 centers currently providing evidence-based services [35]. Key efforts include engaging young people in service design and planning to improve responsivity to youth needs and minimize stigma, building an integrated community network, improving the availability of programs that teach resilience and core competencies (e.g., interpersonal skills), identifying those at risk for mental health problems earlier, ensuring clearly defined pathways to care, and engaging community leaders [34,36].
In England, Forward Thinking Birmingham advocates prevention, choice, and personalized care and offers youth a range of new services and facilities; this model will likely serve as a United Kingdom template for additional youth mental health service reform efforts [13]. Forward Thinking Birmingham is based on the success of pilot initiative Youthspace, which explored effective clinical approaches among youth up to age 25 [37]. Goals included providing rapidly responsive, youthfriendly early intervention services and utilizing a range of treatments.
New Zealand's Youth One Stop Shops were developed independently in response to local needs and opportunities supported by relationships with other providers and funders, though they share a common goal of promoting youth access to healthcare and social services [38]. In 2009, there were at least 14 Youth One Stop Shops across the country, providing a range of youth-friendly, holistic services at little or no cost to the youth.
Several ICYSH efforts are underway in Canada. ACCESS Open Minds is implementing 14 ICYSHs in urban and rural areas across Canada [13,39,40]. The multi-stakeholder ACCESS network includes youth, families, community organizations, service providers, researchers, and policy makers, and provides rapid access to evidence-informed, youth-friendly services appropriate for varying levels of need [40,41]. Foundry is a British Columbia model that co-locates health and social services through a network of centers and e-health services [42]. By supporting communities to develop youth-friendly ICYSH storefronts, working with provincial resources, and linking to specialized services and community agencies, Foundry aims to strengthen a comprehensive system of care for youth and young adults provincially and improve access to mental health, substance use, and primary care services [43]. YouthCan IMPACT in Toronto involves the development, implementation and evaluation of an Integrated Collaborative Care Team (ICCT) model consisting of linked components that are co-located within community-based, youth-friendly ICYSHs [44].
Most models identified a focus on intervening during early stages of distress, possibly before diagnostic criteria are met [13,36,39,40,43,51,52]. In headspace centers, mood and anxiety symptoms and disorders were the most common presenting problem [46,[52][53][54][55], although formal diagnosis was available for only few clients [46]. Additionally, 69-73% of headspace youth presented with high or very high levels of psychological distress [46,48], and 19-29% of young adult clients were not engaged in education, employment or training [46,56]. Jigsaw similarly reported seeing youth with high levels of psychological distress [49], with four main types of issues identified among youth: developmental, comorbid, anxious and externalizing disorders [57].

Settings
Documents varied in the level of detail provided about service settings. Several documents emphasized efforts to make settings accessible to youth, non-stigmatizing, and youth-friendly. For example, some programs were located in shopping centers and storefronts and involved youth in decisions about design and décor [43,58]. Others were centrally located or close to public transportation [31,38,50]. In headspace centers, physical aspects of the settings described as youth-friendly include couches and bean bag chairs, colorful walls and creative artwork for a vibrant look, and an open waiting area and high ceilings to promote a feeling of safety and openness [59]. Youthfriendly environments were key for Foundry, including an informal, non-clinical space where youth can spend time with peers in addition to attending appointments [43]. Jigsaw discussed plans to develop a youth café with a public youth space and a program delivery area [34]. Some headspace centers encourage recreational use with pool and air-hockey tables [60].

Service providers
Documents describing the types of service providers typically include a range of professionals from several disciplines. For example, the intensive mobile youth outreach service subprogram of Orygen Youth Health consists of two psychologists, two social workers, one occupational therapist, one psychiatric nurse, and a part-time consultant psychiatrist [61]. Very few documents provided detailed information about service providers' roles. Within New Zealand's Youth One Stop Shops, several services are offered by physicians, nurses, counsellors, social workers and youth staff [62], providing primary care, sexual and reproductive health, mental health, drug and alcohol services, counselling, smoking cessation, family planning, and health promotion and education services [38]. For the Foundry prototype, primary care and sexual health services are provided by general practitioners and nurse practitioners, mental health services by psychiatrists, and substance use counseling by social workers and nurses. Additionally, partnerships provide other services, including psychosocial rehabilitation, housing support, income assistance, and peer support. ACCESS Open Minds clinicians include professionals with psychology, nursing, social work, or occupational therapy backgrounds who assess youth needs and provide need-based care [40,43]. In YouthCan IMPACT, each integrated collaborative care team includes youth workers, social workers, psychiatrists, nurse practitioners, peer support workers, access to primary care providers, and a care navigator [52]. For higher-risk youth, psychiatrists and/or nurse practitioners provide psychiatric assessment and medication management, along with other clinically appropriate interventions. Several ICYSH models in this review included peer support workers as service providers [38,40,43,52,63], reflecting the importance of youth with lived experience supporting other youth experiencing similar issues.
Many documents did not provide information on their service provider training process. Some documents broadly indicated that there is training in evidence-based interventions and best practices [36,59,64], in working with youth and youth-friendly approaches [59,65], and professional development or continuing education activities [38,66,67], though difficulties with releasing staff for professional development opportunities were also noted [38]. Some documents mentioned ongoing supervision and regular team meetings [51,68]. As part of Jigsaw, a structured training program addresses adolescent development and mental health, strengths-based and solution-focused approaches, risk assessment, goal setting, crisis response, interagency working and collaboration, consultation processes, and integrated planning and evaluation [34]. Initial training ensures a shared understanding of the Jigsaw philosophy and implementation process, with the plan of extending the training more broadly to others in the community who work with youth to increase service capacity.

Services and interventions
More information was provided on broad types of services included in ICYSHs than on specific interventions ( Table 2). headspace includes four core service streams: mental health, drug and alcohol services, primary care, and vocational assistance (e.g., [31,69,70]). Primary care is a component of several other models (e.g., [38,43,71]). Social services, including vocational assistance, education and training support, and housing support were a component of other models [37,38]. Several models use brief, solution-focused interventions (e.g., [13,34,37,45,52]), as well as peer support and mentoring (e.g., [34,52,72]). Some models provided information on specific psychosocial interventions utilized. Services provided by Jigsaw include case management, problem-solving, mindfulness, cognitive-behavioral therapy (CBT), substance use services, psychoeducation, and social skills [57]. In headspace centers, CBT was reported to be the most common treatment provided for all presenting concerns, followed by supportive counseling and psychoeducation [73]. In YouthCan IMPACT, standardized protocols are used for interventions including solution-focused brief therapy (SFBT) and group dialectical behavioral therapy (DBT) skills [52]. Early intervention approaches for psychosis including CBT were mentioned as part of enhanced headspace services, ACCESS Open Minds, and Orygen Youth Health [13,14,41]. ACCESS Open Minds provides services depending on a youth's needs, including specific therapies (e.g. DBT for emotion dysregulation), transition to a specialist service (e.g. eating disorder program), or admission to a hospital (e.g. high risk of suicide) [40]. Some documents mentioned the use of evidence-based approaches, but not specific interventions (e.g., [42,49]). For example, an independent headspace evaluation interim report indicated that implementation efforts were prioritized over tracking the extent of use of evidence-based treatments [74].
Intake and assessment processes were described in some papers; however, little information was provided on the use of standardized assessment measures. One exception, however, is the use of Kessler Psychological Distress Scale (K-10), Clinical Global Impression (CGI) scale, and the Social and Occupational Functioning Assessment Scale (SOFAS) by ACCESS Open Minds clinicians as part of a measurement-based care approach [40]. Some models mentioned following a stepped-care or clinical staging model (e.g., [51,52]). Other work did not use this terminology, but described analogous processes. For example, headspace interventions are said to be delivered according to severity and complexity of an individual's needs [64]. Some documents discussed personalized treatment plans [37] and person-centered approaches [42].

Infrastructure and care coordination
Infrastructure aspects included use of health registries, outcome tracking, information sharing through electronic records, and cross-organization administrative processes, although many documents did not discuss infrastructure.
The Foundry model uses a centralized infrastructure and structured processes that coordinate ongoing collaboration, such as data capture systems that support crosspartnership service integration, clinical care, research, and evaluation [43]. Tele-health and information sharing guidelines are promoted to increase the effectiveness and coordination of team-based care [75,76]. At headspace, data are collected through a minimum dataset process in which all youth accessing centers and their service providers enter data electronically at each service occasion [31,46]. The headspace national office is responsible for infrastructure efforts including developing funding and assessment guidelines, negotiating contracts, developing reporting structures and key performance indicators, and providing policies and tools including partnership documentation, memorandums of understanding, governance guidelines and a business model guide [74]. In Jigsaw, youth data are captured through an online system that records clinical, case management, service delivery, and outcome-related information [49]. The use of a single, shared health record to facilitate collaboration and streamline care was mentioned in several documents (e.g., [58,66,72]). Shared infrastructure has been identified as positively contributing to service coordination and integration [74].
Other methods of care coordination include identifying point persons to facilitate service access and coordinate care across specialists, with titles such as care navigators, youth workers, and youth access clinicians [38,51,52,77]. These workers engage in activities such as exchanging information and participating in joint coordination meetings and planning activities [74]. Some models discussed the role of support or outreach workers in linking clients to services outside the ICYSH and maintaining connection and follow up [34,72]. Coordinating external referral pathways was viewed as helpful by youth accessing headspace services [59] and care coordination is a key headspace performance indicator [70].

Common principles of integrated care models
Several common principles of ICYSH models were discussed, including improving access to care and early intervention, youth and family engagement and participation, youth-friendly settings and services, evidenceinformed approaches, and partnerships and collaboration (Table 3).

Improving access to care and early intervention
A number of programs emphasized timely access to care, with the ACCESS Open Minds providing access to assessment within 72 h and appropriate care within 30 days [40,41], the Forward Thinking Birmingham Program providing rapid response and assessment within 1 week [13,37], and the Orygen Youth Health program providing a 24/7 triage, assessment and crisis response [14]. In addition, diverse access pathways were provided, e.g., self-referral [14,31], walk-in or drop-in services [41][42][43][44], and online access to services [48] including telemedicine [41,42]. Similarly, a number of programs highlighted the importance of early intervention [14,31,34,36,39,43,52,78] and some included clinical staging [78] or stepped-care [52] to provide services at the earliest stage necessary.

Partnerships and collaborations
Another core value was forming partnerships and collaborations with a diverse set of agencies. Most programs had partnerships with various stakeholders including youth, families, service providers, community agencies, researchers, hospitals, policy makers, etc. [13,14,31,41,43,52]. Partnerships help provide multidisciplinary, co-located services [38] including social, educational, employment services [14], housing support, income assistance [43] and other specialist services [78]. A social network analysis of the headspace staff reported interprofessional collaboration existed in both routine and uncertain situations [81]. In addition, a study conducted with internal and external staff of Youth One Stop Shops reported that individual staff 's trusting personal relationships was crucial for successfully overcoming agency differences, and collaborative care was found to be essential to the successful care of youth with high needs [82].

Outcome research and program evaluation
Overall, research on youth MH or functional outcomes following intervention was limited, with only 11 documents reporting outcomes (Table 4). One additional article reported youth outcomes; however, the focus was on evaluating an intensive mobile outreach subcomponent rather than overall integrated care [83]. Outcomes reported were predominantly short-term, with long-term follow-up data lacking. Only one evaluation (non-RCT) included a comparison group [84], and few studies provided comparative outcome data to contextualize the magnitude of reported outcomes (exceptions: [51,73]). Methods of measuring outcomes varied; however, several studies reported using standardized self-report and clinician-rated measures [45,51,73,[83][84][85][86]. Three documents provided some outcomes information, but did not specify the measures used [37,38,87]. In addition to the 11 documents with youth outcome information, three articles reported on case study findings; of them, one utilized a standardized self-report measure [65], whereas two did not [61,78]. Seven documents discussed future outcome measurement plans, spanning a total of three ICYSH models, all in Canada [13,39,41,43,44,52,88]. Generally, positive outcomes, particularly improvements in psychological distress and psychosocial functioning have been found [37,45,73,84]. Additional evaluation projects are under way by ACCESS Open Minds using a stepped-wedge design [39,40] and YouthCan IMPACT using a pragmatic randomized controlled trial [52]. ACCESS Open Minds and the Foundry also plan to

ACCESS Open Minds
Provides timely access, early identification [39,40] Employs clinician as single contact point for direct, rapid access to assessment (72 h; [40,41]) Utilizes telemedicine for rapid remote assessment [40,41] Requires no referral or specific symptom [40,41] Engages youth and families in project conceptualization, core values, implementation, and research [39,40] Includes youth as full care partners and encourages participation of youth and families at all levels (e.g., peer support, service planning, evaluation, research [40,41]) Commits to a youth-friendly, empowering culture [40,41] Offers youth-friendly physical spaces called Youth Space as portals for help-seeking and venues for peer support activities [13,40] Provides access to evidenceinformed mental health care [39] Utilizes needs-based staging model [40,41] Generates evidence and tests effectiveness of service model [13,40] Forms coalition of partners integrating research into care [39,40] Includes network of youth, family/carer, community, service provider, researcher, and policy/decision maker stakeholder groups [40,41] Utilizes partnerships with emergency/hospital services [40,41] Forward Thinking Birmingham Provides rapid response and assessment/diagnostic formation to GP within 1 week [13,37] Improves access to effective support and provides range of services based on principles of prevention/early intervention [13] Consults extensively with youth and conducted qualitative research on experiences with existing services [14] Designs website for advice, education, and individualized assessment based on youth input [14] Emphasizes non-stigmatizing, youth-friendly environments and services [37] Uses CBT as default evidence-based intervention [14] Leverages partnership with agency focused on education, skill training, entrepreneurship, social inclusion and employment [14] Creates consortium of NHS partners (child/adult services), voluntary sector, and private healthcare organization [13] Foundry Improves access to youth mental health, substance use, and primary care services [43] Offers drop-in services [43] Provides online access and local walk-in centers [42] Improves service providers' and community members' knowledge of how to access services [76] Includes prevention and early intervention as core service components [43] Designs service delivery and makes decisions with youth participation to reduce service barriers, better meet needs, and promote youthfriendly approaches [43] Involves youth in staff recruitment; utilizes Youth Advisory Groups [43,98] Promotes engagement activities (e.g., focus groups and journey mapping) to make youth and families' experience central to the process [75,79] Utilizes youth-friendly storefronts, non-stigmatizing centers; offers accessible hours and preferable locations [43] Employs friendly health and service providers [42] Utilizes evidence-based best practices [42] Uses integrated e-health based on emerging evidence [43] Links expanded implementation to outcomes and evaluation results [43] Forms governing council based on partnership of several organizations [43] Utilizes partnerships for peer and housing support, income assistance, phone/chat/email/ text supports, and online therapies [43] Plans collaborations for public health approaches and Aboriginal youth needs [43] Partners with school districts and communities for mental health awareness [75]   headspace Offers highly accessible model of care [30,31] Provides physical health services to allow for stigma-free access point [14] Utilizes clinical staging approach to support early and preemptive intervention [90] Develops national and local youth participation initiatives [31,59] Consults youth advisory groups about various matters (e.g., youth friendly environment, staff recruitment, operational decisions; [31,59,74]) Solicits feedback from youth and families through exit surveys, audits, websites and social media, feedback box, and focus groups [31,70,80] Promotes youth decision making about care and peer support [31,106] Assesses satisfaction and identifies barriers [80,110] Prioritizes youth participation to achieve youth friendliness [74] Creates youth-friendly atmosphere: youth art, structural building changes, youthfriendly location, information of interest to youth in waiting area [31,70] Facilitates youth participation in mental health care via physical set-up of clinics and being made to feel welcome by all staff [31,60] Provides evidence-based care within a clinical staging framework [31,90] Utilizes CBT-based interventions for depression, anxiety, and psychosis, and motivational interviewing and behavior contingencies for substance use [90] Provides CBT most often for all primary concerns [73] Plans to produce evidencebased resources to support sites in using evidence-based practices [90] Designs and develops model with input from consortium of research and academic institutes, practice network, and psychological society [90] Links to local specialist services, schools, and other communitybased organizations [31,90] Identifies key agency to lead each center on behalf of local consortium of organizations who coordinate and deliver four core service streams [14] Jigsaw Offers diversity of access pathways, often self-and parentreferral [14,57] Provides central location and immediate response [34] Offers accessible prevention and early intervention services [34,36] Engages youth in design, implementation, and review of programs and conducted extensive youth consultation process [34,57] Involves Youth Advisory Panel at each site and Youth Participation Officer in design and planning process of each initiative [34] Engages youth to increase likelihood services are relevant, stigma-free, and accessible [36] Sees youth in their usual settings; plans youth café facility [34] Consults youth on creating welcoming and approachable sites (e.g., colour schemes, language to describe program, process for entering site, balance between professional and relevant for youth; [36]) Offers youth-friendly, storefront drop-in center [120] Supports service providers in providing evidence-based, best practice approaches [36,57] Exposes sites to youth mental health literature to promote adoption of best practices and reviewed evidence-based programs and research literature in development process [36] Fosters partnerships among services [36] Engages and partners with all relevant stakeholders, includ- ing key statutory, community, and volunteer agencies, and establishes new partnerships [14] Develops positive partnerships with government [34] Orygen Youth Health Matches target age with peak MH onset [12] Provides early intervention for psychosis, mood disorders, and borderline personality disorder [14] Offers 24/7 triage, assessment, and crisis response [14] Facilitates regular meetings of current and past clients to improve service, produce newsletter, and participate in selecting staff [63,122] Offers mobile outreach services (IMYOS) for high-risk youth with complex needs and history of poor engagement with clinic-based services [61,78,83] Provides flexible interventions and engages family [124]; designs interventions with youth and families' guidance [61] Advocates youth-friendly approaches within IMYOS [61] Fosters youth-friendly culture [14] Provides peer support drop-in room [63,122] Provides evidence-based mental health care [14] Focuses on development and delivery of bestpractice interventions within IMYOS, though overall approach without documented evidence base [61] Uses cognitive therapy routinely [61] Links with other mental health and general support agencies essential to ensure quality service delivery [14] Provides pilot forensic services through consulting clinicians from specialist institute [123]   YouthCan IMPACT Offers MHA services within walkin clinic/one-stop shop [44] Improves access to timely services through communitybased stepped-care model [44] Provides an early, low intensity intervention through solutionfocused brief therapy [52] Develops model with key participation of youth and family members with lived experience of the mental health system [52] Engages youth in all aspects of the project, such as designing the research study, (i.e., advising how to measure improvement) and choosing clinical services offered [88] Provides services in youthfriendly environments in the community [52] Links several evidenceinformed components within model [52] Includes evidence-informed interventions, namely, solution-focused brief therapy, youth-and familyfocused DBT, and peer support [52] Develops model in partnership with several community agencies, adolescent psychiatry departments, academic collaborators, and other stakeholders [52] Partners with outreach services and targeted intervention programs [52] Encourages partners to join a common culture and respects unique strengths [44] Youth One Stop Shops Promotes access to range of health care and social services [38] Improves access through outreach, mobile, satellite services, and/or evening hours; provides transport at times [38] Offers services in central locations, close to public transport and other places youth frequent [38] Utilizes youth workers to serve as a communication bridge [38] Opens site with youth-driven efforts: commissioning needs analysis, forming a trust and lobbying for funding, and employing staff [126] Facilitates youth focus groups; involves youth in activities such as designing a youth health information card [65] Involves youth at all levels (e.g., service evaluation, decision-making processes [38]) Offers youth-friendly opening hours to accommodate school and work [38] Provides facilities attractive to youth (e.g., couches, music, recreational activities; [38]) Employs staff skilled in interacting with youth, responding to needs [38,127] Utilizes CBT [65] Links with several organizations formally and informally within and outside the health and disability sector; allows for varying types of relationships and information exchange [38,127] Enables through linkages colocation of services, collaboration on community projects and events, development of resources, and cross-trainings [38] Facilitates    test the effectiveness of the individual interventions being used [13,43], adding to the intervention evidence base.

Discussion
This scoping review identified international ICYSH models for addressing youth MH needs. Common principles and characteristics of these models are summarized. This review provides a synthesis of the components of such models and can serve as a foundation for informing replication, evaluation and implementation of ICYSHs, which have been rapidly proliferating [13,14]. However, limited information was provided in many domains, raising questions about the availability of sufficient detail to achieve these goals. ICYSH models showed some similar characteristics, providing a starting point for replication. Many have focused on early intervention for adolescents and young adults [14,34,36,39,43,52,78], and on addressing the unmet need for services across the transition to adulthood [12]. Nearly all models reported trying to develop non-stigmatizing, youth-friendly environments [89]. Reported efforts were consistent with recommended approaches for improving accessibility and youth-friendliness laid out within calls for youth mental health services reform [90]. Little information was available on service providers' training or specific roles. More information was provided on broad services categories, with mental health, drug and alcohol services, primary care, vocational or other social services, and peer support featured in several models. Evidence-based and brief, solution-focused interventions were promoted, but specific interventions, extent of their use and achievement of fidelity were rarely reported. Some information was identified on care coordination and infrastructure, such as administrative processes, information sharing, and outcome tracking, although many documents did not discuss these aspects. Overall, the variability in the level of detail provided for several of the characteristics examined precludes drawing strong conclusions regarding the extent of differences across models, and does not allow for clear direction regarding replication, evaluation of these components, nor wide scale implementation. Future reporting should follow TIDieR guidelines in order to facilitate replication, evaluation and implementation [91].
However, there was clearer consistency in the aims of ICYSH models. Improved access to care and earlier intervention were frequently highlighted and served as catalysts for model development. Engaging youth and families in service delivery and design were universally evident. Youth-friendly services and environments were emphasized within all models. Disseminating evidenceinformed interventions to more youth in need and implementing evidence-based care were also consistently identified. Finally, leveraging partnerships and collaborations to provide multidisciplinary, integrated services or community capacity building was common. Details regarding the 'how' of effectively achieving these aims, however, were limited, thus falling short of providing the information required for replication, evaluation and implementation-related decision-making. For example, the literature is lacking sufficient information on the formation and maintenance of partnerships and related agreements, decision-making processes, and fidelity to evidence-based interventions. Moreover, although integration was frequently mentioned as an aim, there was little explanation of how services are integrated on a structural level beyond the role of care coordinators, and measurement of service integration was lacking.
Notably, the review also revealed potential limitations of these models of care. Specifically, limited service availability [33] and workforce shortages [92] are challenges for the field more broadly and also impact ICYSHs. Additionally, several studies suggest that at least some of the youth presenting for services were experiencing more distress and impairment than models may have been primarily designed to address [49,51,59,93], which is a key finding that should be taken into account in the design and development of robust ICYSH models that can meet the needs of all presenting youth. The complexity of managing numerous objectives and components within a comprehensive ICYSH may limit the ability to fully address each aspect simultaneously.
This review also identified a number of other limitations of the literature. Notably, rigorous evidence of improved youth outcomes attributable to these models of care is scarce. The limited outcome research identified was short-term and lacked control groups (see [19] for a thorough review). All models are from high-income countries, limiting generalizability. Also important to note is the limited translating of work into publications; for some models, the bulk of information was derived from grey literature sources. Finally, numerous relevant documents were not captured using integration-focused search terms (see Appendix), raising questions about terminology consistency.

Implications for research
This review highlights the pressing need for more rigorous research examining youth outcomes within ICYSHs. Notably, robust designs are needed to evaluate both the effect of ICYSHs on youth outcomes and cost-effectiveness compared to usual treatment. Such efforts are underway for the YouthCan IMPACT program, which is comparing ICYSHs to hospital-based adolescent psychiatric services [52]. ACCESS Open Minds includes a cluster RCT design to evaluate implementation processes, but not youth health outcomes [41]. Additional comparative effectiveness trials comparing treatment outcomes within different ICYSH models, utilizing different control interventions, would strengthen the literature (see also [19]). Given that much information was derived from grey literature, findings also suggest the need to translate more of this work into peer-reviewed publications to facilitate replication and rigorous evaluation. Publications regarding ICYSHs need to include greater detail regarding key attributes, especially those considered unique to the model, such as integration of care, partnership agreements, integrated decision-making processes and youth friendliness to allow for replicability [94]. In addition, supplementary material could be provided on project websites to more thoroughly describe models in a level of detail often not possible within the framework of academic publications. Given the lack of detail on certain aspects of these models, there is insufficient information currently available in these areas to guide implementation.
Utilizing common language and terminology regarding service integration would also improve information sharing and replicability. Reaching a consensus on the most essential elements of these models should be prioritized, for example the types of early interventions that should to be included, but also other characteristics such as types of service providers and other site features. Findings from this review will inform the appraisal of key features of such models, as does the recent review by Hetrick et al. [19]. Additionally, research within established programs could address challenges related to delivering and tracking the use of evidence-based practices in community settings. Finally, using common, core outcome measures [95] to track outcomes and other aspects of ICYSHs would help facilitate collaborative research efforts, support future meta-analyses, and more rapidly advance the field.

Implications for practice
The finding that youth are presenting to ICYSHs with high levels of distress and impairment-some with more serious needs than models were designed for-has implications for service availability, accessibility, resource allocation, and training. If ICYSH models become a default "stop gap" for youth with more serious difficulties due to a lack of appropriate services elsewhere, their ability to address the needs of youth with emerging MH concerns may be limited. Having clear processes in place supporting a no-wrong-door approach and linking youth with the most appropriate services could lessen these concerns. Leveraging existing service relationships and creating new linkages may be necessary to ensure that youth receive appropriate, comprehensive, multidisciplinary services. These linkages may cross academic-community divides, which may require new ways of working collaboratively (e.g., medical vs. community mental health model). Finally, defining a core basket of services for ICYSH models, as is being discussed in the broader mental health services field (e.g., [96]), will also be important for clarifying the needs that can effectively be met and ensuring that service providers receive appropriate specialized training.

Implications for policy
This literature synthesis can guide policymakers interested in transforming the youth mental health service system through ICYSH implementation. Policymakers should be aware of the identified deficits in the mental health service system driving the development of ICYSH models and their potential to address these pressing concerns. Policy planning, communication, and funding complexities should be taken into account since comprehensive, cross-sectoral services may span multiple government departments (e.g., youth services, health services, education). Policymakers should be aware that creating ICYSH models does not necessarily require building new services, but can be accomplished by integrating existing services and leveraging existing partnerships, which is encouraging for financial feasibility.
Although much remains to be determined, particularly with regard to outcomes, the profiles of youth best served by such models, cost-effectiveness, and optimal components, this review provides a starting point for understanding the common characteristics of ICYSH models that are likely to be important targets for replication, evaluation, service development efforts and funding. Research granting agencies are encouraged to support rigorous evaluations of ICYSH models to further inform development. Results from economic analyses (e.g., [41,52]) will have particularly important implications for policy decisions. Policymakers are encouraged to continue to monitor this burgeoning field for enhanced guidance as they develop and expand ICYSHs internationally.

Limitations
There are limitations of this review that warrant consideration. Although efforts were made to ensure that the review is as thorough and comprehensive as possible, there is inevitably unidentified relevant literature. In particular, the grey literature search was representative, not exhaustive. Additionally, this review was limited to English publications. Documents were found to originate from high-income countries. This may affect the generalizability of the findings to low-or middle-income countries. Information was generally not available on funding models supporting the various ICYSH initiatives; this should be further explored to support new implementation initiatives. To allow for in-depth examination of ICYSHs, this review did not include literature on integrating behavioral health services into existing primary care or school settings, although there may be relevant findings from these areas. Aspects of primary care or school-based models should also be considered in future research to determine the ideal setting. Finally, in accordance with scoping review methodology [21], the quality of studies included in this review was not assessed.

Conclusions
This review brings together literature on ICYSH models for youth MH from diverse sources and examines their common principles and characteristics. ICYSHs are poised to address many of the most pressing youth mental health service concerns by uniting traditionally fragmented services into single, youth-friendly settings, improving early access to evidence-informed interventions, engaging youth and families, and drawing on the strengths of cross-disciplinary and multi-sectorial collaborations. Future efforts to provide comprehensive descriptions and replicate these models, evaluate youth outcomes and identify the most critical components and processes for ICYSHs will further strengthen these models of care.