["Health Expectations, Volume 29, Issue 3, June 2026. ", "\nABSTRACT\n\nIntroduction\nThere is growing recognition of the methodological benefits of co‐producing adolescent mental health research. Co‐production supports the development of study methodologies that are more relevant and appropriate for the examination of adolescents' mental health.\nWithin this article, insights from the Mental Health in the Moment Young Person Advisory Group (MHIM‐YPAG) are presented in relation to which mental health constructs, predictive factors and measures were endorsed by young people for inclusion in a mental health study. The aim of this paper is to provide guidance to researchers, highlight the benefits of co‐production and provide a template for co‐production in mental health study measures.\n\n\nMethods\nMembers (n = 18) took part in online ‘focus group style’ sessions covering constructs, predictive factors and measures related to adolescent mental health. They were asked to discuss and then individually rank a set of constructs, predictive factors and measures from most to least relevant. Following this, a semantic thematic analysis of session materials was performed by researchers and findings were verified by MHIM‐YPAG members.\n\n\nResults\nMembers emphasised the importance of general and specific constructs that reflected both positive and negative traits. In addition, they emphasised the importance of examining suicidality/suicide‐ideation. Social media, academic stress and relationships were the most relevant predictive factors for this group. Language use and response scale length were important when deciding measures appropriateness.\n\n\nConclusion\nThis paper highlights the importance of involving young people as co‐producers within adolescent mental health research. Benefits include improving the appropriateness and relevance of the study design. Insights may act as a guide for researchers involved in adolescent mental health research.\n\n\nPatient and Public Contribution\nThe ‘MHIM‐YPAG’ was established to enable the involvement of young people to co‐produce the MHIM project. Thus, this paper details the insights made by the MHIM‐YPAG regarding the inclusion of specific mental health constructs, predictive factors and measures. As detailed in the MHIM‐YPAG protocol paper, young people will be involved through the 5‐year project in a co‐production capacity.\n"]