Who gets included? Equity in digital and decentralised mental health and neurodevelopmental trials: A systematic review

Decentralised clinical trials (DCTs) may help address underrepresentation in digital mental health research, but their effectiveness in reaching underserved populations is unclear. This review assessed the reporting of equity-relevant demographic data in DCTs to identify groups at risk of exclusion and barriers and facilitators to inclusive participation. A systematic search was conducted in MEDLINE, PsycINFO, Embase, CINAHL, Cochrane Central Register of Controlled Trials, and Web of Science. We included studies reporting on mental health interventions evaluated via remote, online, virtual, or hybrid DCTs, published in English from 2020-2026 (last search date: 01/07/2025), that reported participant demographics. Demographic data were extracted and summarised according to the PROGRESS-Plus framework. Demographic frequencies were compared to national population statistics. Thematic analysis identified barriers and enablers to inclusive participation in DCTs. Fifty-nine papers reporting 57 DCTs were included. Studies involved a range of mental health and neurodevelopmental conditions across the ages. Gender (100%) and age (100%) were universally reported. Reporting of other PROGRESS-Plus variables across the 57 DCTs was limited: social capital (43.9%); race/ethnicity (40.4%); occupation (36.8%); socioeconomic status (35.1%); place of residence (12.3%); religion (5.3%), and non-mental health disability (1.8%). Participants from ethnic minority backgrounds, males, unemployed individuals, and those with lower educational attainment were consistently underrepresented. While rural populations were better represented in Australian studies, data on poverty, religion, and social capital were limited and varied in representativeness. Most studies focused on adults aged 18-50 years. Thematic analysis identified key barriers including, digital exclusion, low digital literacy, cognitive and sensory challenges. Facilitators included therapist or navigator support and simplified onboarding. Equity variables are persistently underreported. DCTs do not effectively engage underserved populations in mental health research, meaning digital interventions are evaluated on unrepresentative samples. This risks perpetuating, and exacerbating, existing health inequalities, limiting the real-world impact of digital mental health solutions.