TY - JOUR AU - I. Bouchard AU - K. Martinez AU - P. Gomez-Patino AU - F. Navarro AU - L. Brookman-Frazee AU - K. J. Holmquist AU - S. Negriff AU - M. Barnett AU - S. Broder-Fingert AU - N. A. Stadnick A1 - AB - Autistic youth often experience co-occurring mental health needs, yet they have multi-level barriers to accessing needed care. To address these barriers, the ATTAIN NAV (Access to Tailored Autism Integrated Care through Family Navigation) intervention was co-designed with caregiver and healthcare partners and delivered by lay health navigators to facilitate access to and engagement with mental health services for school-age autistic youth. This manuscript describes the multi-method, partner-engaged, longitudinal adaptation process to (1) identify intervention content and implementation refinements prior to the hybrid trial and (2) track ongoing research, intervention, and implementation adaptations during the trial and their impacts on study outcomes. The adaptation processes used the Framework for Reporting Adaptations and Modifications to Evidence-based Implementation Strategies (Miller et al., 2021) to guide data collection and evaluation approaches. From the qualitative co-design activities with caregivers (n = 5), primary care providers (n = 6), developmental care clinicians (n = 4), and health informatics staff (n = 3), several intervention content and implementation adaptations were identified and integrated prior to the trial. From the longitudinal adaptation tracking process during the trial, a total of 19 adaptations were documented throughout the implementation trial. The adaptations were related to maintaining the feasibility and acceptability of the study procedures (32%), increasing family recruitment/engagement (26%), increasing the acceptability of the intervention components (16%), increasing physician recruitment/engagement (11%), expanding mental health resources (5%), complying with partnered healthcare organization policy (5%), and increasing navigator workflow efficiency (5%). Findings offer a structured and replicable approach adoptable by non-traditional mental health intervention and implementation research. AD - Department of Psychology, California State University Northridge, Northridge, CA, USA. isaac.bouchard.551@my.csun.edu.; Doctoral Program in Clinical Psychology, San Diego State University, University of California San Diego Joint, San Diego, CA, USA.; Child and Adolescent Services Research Center, San Diego, CA, USA.; Department of Psychiatry, University of California San Diego, La Jolla, CA, USA.; University of California San Diego Altman Clinical and Translational Research Institute Dissemination and Implementation Science Center, La Jolla, CA, USA.; Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.; Kaiser Permanente Bernard J Tyson School of Medicine, Pasadena, CA, USA.; Department of Counseling, Clinical, and School Psychology, University of California Santa Barbara, Santa Barbara, CA, USA.; Department of Pediatrics, University of Massachusetts Chan Medical School, Worcester, MA, USA. AN - 40488794 BT - Adm Policy Ment Health C5 - Healthcare Disparities; Education & Workforce DA - Jun 9 DO - 10.1007/s10488-025-01452-z DP - NLM ET - 20250609 JF - Adm Policy Ment Health LA - eng N2 - Autistic youth often experience co-occurring mental health needs, yet they have multi-level barriers to accessing needed care. To address these barriers, the ATTAIN NAV (Access to Tailored Autism Integrated Care through Family Navigation) intervention was co-designed with caregiver and healthcare partners and delivered by lay health navigators to facilitate access to and engagement with mental health services for school-age autistic youth. This manuscript describes the multi-method, partner-engaged, longitudinal adaptation process to (1) identify intervention content and implementation refinements prior to the hybrid trial and (2) track ongoing research, intervention, and implementation adaptations during the trial and their impacts on study outcomes. The adaptation processes used the Framework for Reporting Adaptations and Modifications to Evidence-based Implementation Strategies (Miller et al., 2021) to guide data collection and evaluation approaches. From the qualitative co-design activities with caregivers (n = 5), primary care providers (n = 6), developmental care clinicians (n = 4), and health informatics staff (n = 3), several intervention content and implementation adaptations were identified and integrated prior to the trial. From the longitudinal adaptation tracking process during the trial, a total of 19 adaptations were documented throughout the implementation trial. The adaptations were related to maintaining the feasibility and acceptability of the study procedures (32%), increasing family recruitment/engagement (26%), increasing the acceptability of the intervention components (16%), increasing physician recruitment/engagement (11%), expanding mental health resources (5%), complying with partnered healthcare organization policy (5%), and increasing navigator workflow efficiency (5%). Findings offer a structured and replicable approach adoptable by non-traditional mental health intervention and implementation research. PY - 2025 SN - 0894-587x ST - Multi-Method, Partner-Engaged Process to Document Adaptations for ATTAIN NAV: Family Navigation for Autism and Mental Health T1 - Multi-Method, Partner-Engaged Process to Document Adaptations for ATTAIN NAV: Family Navigation for Autism and Mental Health T2 - Adm Policy Ment Health TI - Multi-Method, Partner-Engaged Process to Document Adaptations for ATTAIN NAV: Family Navigation for Autism and Mental Health U1 - Healthcare Disparities; Education & Workforce U3 - 10.1007/s10488-025-01452-z VO - 0894-587x Y1 - 2025 ER -