Incentivising participation in mental health app research: lessons learned from a mixed methods randomised controlled trial

Background User engagement is recognised as a critical and pervasive challenge that has limited the potential evidence base being developed for mental health apps. Aim To understand young people’s motivations for participating in a randomised controlled trial for a mental health app and the role of intrinsic (e.g. improving well-being) and extrinsic (e.g. financial incentives) drivers in engagement. Method Emotional Competence for Well-Being (ECoWeB) was a superiority parallel three-arm randomised cohort trial recruiting a cohort of 16–22 year-olds across the UK, Germany, Spain and Belgium, who, depending on risk, were allocated respectively to the PREVENT (n = 1262) versus PROMOTE (n = 2532) trials. We conducted in-depth semi-structured interviews in the UK (n = 18, mean age = 17.7, s.d. = 1.5) and Spain (n = 11, mean age 20.6, s.d. = 1.7) to explore participants’ self-reported motivations and engagement. The trial was registered at ClinicalTrials.gov: NCT04148508. Results Across arms, 21% of participants never set up an account to access the app and approximately 50% did not complete the 3-month follow-up assessment. Engagement was not significantly higher in the intervention arm compared to the control arms across metrics. Qualitative findings demonstrated that although extrinsic factors alone may be enough to prompt someone to sign up to research, intrinsic drivers (e.g. finding the app useful) are needed to ensure longer-term engagement. Conclusions Incentivising participation in clinical trials needs to be consistent with incentives that might be utilised at the point of dissemination and implementation to ensure that findings are replicated if that intervention is adopted at scale.