The goal of this study is to conduct a pilot test of a mental health support program called the Youth-Nominated Support Team - Probation (YST-P) for young people ages 12-17 on probation, experiencing suicidal ideation and behaviors (SIB). Young people on probation experience SIB at higher rates than youth in the general population, but often do not receive the mental health care they need due to multi-level barriers. YST-P is adapted from an existing evidence-based, social support intervention, Youth-Nominated Support Team (YST), which is a psychoeducational, social support intervention originally created as an adjunctive to standard behavioral health (BH) treatment for youth with suicide risk following psychiatric hospitalization. YST-P is an adaptation of YST designed to meet the unique needs of youth on probation, addressing their SIB and increasing their uptake of treatment, by leveraging their existing social networks. YST-P is designed as an early intervention program to prevent escalation of SIB and increase probation youths' treatment uptake, bridging them to care. The study entails a single-arm pilot to examine reductions in SIB (within-subject comparison), and increased treatment uptake (comparing YST-P participants to a propensity-matched, historical control). This study will additionally explore theorized mechanisms of intervention action as well as implementation outcomes and barriers/facilitators to YST-P. The goal is for results from this study to inform a larger, fully powered effectiveness trial, as well as future studies leveraging youths' existing social support networks to prevent SIB and bridge them to care.

The goal of YST-P is to improve youths' SIB and their uptake of behavioral health (BH) services (defined as intake +1 session), examining multilevel inner/outer context and bridging factors that influence implementation of YST-P. The proposed hybrid (Type I) effectiveness-implementation study will occur in two counties on Long Island in New York State: Suffolk County and Nassau County. Guided by Heaney and Israel's Social Support for Health (SSH) framework, Social Cognitive Theory (SCT), and the Exploration, Preparation, Implementation, and Sustainment (EPIS) framework, the larger project comprises three phases:

Phase 1: formative qualitative work with key stakeholders.

Phase 2: adaptation (informed by formative work) of existing YST protocols and materials to create YST-P through stakeholder consultant workgroups.

Phase 3 (clinical trial): single-arm YST-P pilot trial, implemented at a community-based BH agency, to examine preliminary evidence of (a) reductions in SIB (within-subject comparison in sample of N=40 YST-P participants), (b) increased treatment uptake (comparing YST-P participants to a propensity matched, historical control, with uptake defined as intake +1 session), exploring theory-driven mediators/moderators (e.g., youth personal factors/coping resources; family environment and resources) on SIB and treatment uptake.

The investigators will additionally examine YST-P implementation outcomes and elucidate multi-level inner/outer context and bridging factors, to inform a larger study. During the clinical trial, investigators will collect quantitative (surveys and structured interviews) and qualitative (interviews and focus groups) data from youth/caregivers, supportive adults, probation staff, and Intervention Specialists at multiple timepoints across the implementation period. Investigators will also collect administrative records data on all youth endorsing suicidal ideation at probation intake, beginning one year prior to YST-P implementation (historical control) and continuing throughout the intervention period.

Inclusion Criteria:

YST-P Pilot Youth on probation, referred to study by YST Intervention Specialist (n=40)

1. Conversational in English (self-report/caregiver)
2. Age 12-17years 11months (self-report/caregiver)
3. Probation involvement (probation staff)
4. Have a caregiver who is willing to participate (caregiver)
5. Endorsed PY suicidal ideation (probation staff)
6. Nominated 2-4 supportive adults, at least 2 of whom are willing to participate (Intervention Specialist, supportive adult)

Caregivers, referred to study by YST Intervention Specialist (n=40)

1. Conversational in English (self-report)
2. Caregiver of a youth who is eligible and willing to participate (probation referral, youth report)

Supportive adults, referred to study by YST Intervention Specialist (n=40)

1. Participating as a supportive adult in YST-P as indicated by completion of YST-P psychoeducational session (Intervention Specialist report)
2. Conversational in English (self-report)
3. Approved by youths' caregiver (caregiver)
4. Be appropriate as determined by the YST-P Intervention Specialist (Intervention Specialist).

Probation staff, assisted by agency leadership (n=15)

1. Conversational in English (self-report)
2. Employed by Suffolk or Nassau County Probation working with youth (self-report/agency leadership)

Intervention Specialists, assisted by agency leadership (n=2)

1. Conversational in English (self-report)
2. Employed by Hope for Youth Licensed behavioral health clinician (self-report/agency leadership)
3. Trained as YST-P Intervention Specialists (Research team)
4. Facilitating the YST-P intervention (Research team)

Exclusion Criteria:

- Participants not meeting all inclusion criteria will be excluded from research activities.