BACKGROUND: There is growing evidence demonstrating the impact of engaging people with lived experience (PWLE) in health research. However, it remains unclear what evidence is available regarding the impact of engagement specific to mental health and substance use research.

METHODS: A scoping review of three databases and thematic analysis were conducted. Sixty-one articles that described the impact of engagement in mental health and substance use research on either individual experiences or the research process were included.

RESULTS: Key topics include (a) the impact of engagement on individual experiences; (b) the impact of engagement on the research process; and (c) facilitators and barriers to impactful engagement. Studies largely focused on the perceived positive impact of engagement on PWLE (e.g., personal and professional growth, empowering and rewarding experience, feeling heard and valued), researchers (e.g., rewarding experience, deeper understanding of research topic, changes to practice), and study participants (e.g., added value, fostered a safe space). Engagement activities were perceived to improve facets of the research process, such as improvements to research quality (e.g., rigour, trustworthiness, relevance to the community), research components (e.g., recruitment), and the research environment (e.g., shifted power dynamics). Facilitators and barriers were mapped onto the lived experience, researcher, team, and institutional levels. Commonly used terminologies for engagement and PWLE were discussed.

CONCLUSION: Engaging PWLE-from consultation to co-creation throughout the research cycle-is perceived as having a positive impact on both the research process and individual experiences. Future research is needed to bring consistency to engagement, leverage the facilitators to engagement, and address the barriers, and in turn generate research findings that have value not only to the scientific community, but also to the people impacted by the science.