Influences on recruitment and retention to mental health randomised controlled trials from the perspective of trial staff: a qualitative evidence synthesis.

Poor recruitment and retention are widely reported as problematic for many randomised controlled trials (RCTs). However, there is limited evidence on the context specific challenges faced by trial staff recruiting to mental health trials. Consequently, evidence to inform effective interventions that could support trial staff in mental health trials is lacking. To address this gap an evidence synthesis is needed to better understand the experiences and influences on trial staff recruiting to mental health RCTs, to inform the development of strategies for improvement. This paper aims to address this gap by synthesising the qualitative evidence on trial staff (e.g. clinicians, researchers) experiences of recruitment and retention to mental health RCTs (trials where mental health is the primary indication under investigation). A rapid qualitative evidence synthesis (rQES) was conducted in accordance with rQES guidance and Thomas and Harden’s approach to thematic synthesis. We searched MEDLINE, CINAHL, PsycINFO, Cochrane Central Register of Controlled Trials, Social Science Citation Index, and Applied Social Sciences Index and Abstracts, Web of Science, as well as key reviews and grey literature. Altogether, 4253 records were screened, resulting in 33 full-text reviews, of which 15 were eligible for inclusion. Confidence was assessed using GRADE-CERQual. The review protocol is publicly available (PROSPERO: CRD42024601854). All studies reported on recruitment, with only one briefly reporting retention data alongside recruitment, therefore findings of this review focus on recruitment to mental health trials. We identified four interrelated analytical themes capturing the influences on trial staff recruiting to mental health trials, extending beyond organisational and trial eligibility issues:- (1) recruitment within existing care pathways; (2) understanding and judgments of RCTs and interventions; (3) weighing decisions to approach patients; and (4) engaging in trial conversations. Findings from this rQES highlight the complex interplay of factors shaping the context-specific challenges faced by trial staff recruiting to mental health trials. Specific concerns that trial participation could destabilise some patients, disrupt care, undermine therapeutic relationships, or trigger risk-taking behaviour were identified as impacting recruitment. Findings highlight key recruitment challenges for trialists to consider in developing interventions to better support staff recruiting to mental health trials.