Recruitment and retention strategies in mental health trials – A systematic review

Background: Recruitment and retention challenges are very common in mental health randomised trials. Investigators utilise different methods to improve recruitment or retention. However, evidence of the effectiveness and efficiency of these strategies in mental health has not been synthesised. This systematic review is to investigate and assess the effectiveness and cost-effectiveness of different strategies to improve recruitment and retention in mental health randomised trials. Methods and materials: MEDLINE, EMBASE, the Cochrane Methodology Register and PsycINFO were searched from beginning of record up to July 2016. Randomised trials involving participants with mental health problems which compared different strategies for recruitment or retention were selected. Two authors independently screened identified studies for eligibility. Results: A total of 5,157 citations were identified. Thirteen articles were included, 11 on recruitment and 2 on retention. Three randomised controlled trials compared different recruitment strategies, none of which found statistically significant differences between the interventional recruitment strategies and the routine recruitment methods. Retrospective comparisons of recruitment methods showed that non-web-based advertisement and recruitment by clinical research staff each have advantages in efficiency. Web-based adverts had the lowest cost per person recruited (£13.41 per person recruited). Specialised care referral cost £183.24 per person, non-web-based adverts cost £372.03 per patient and recruitment via primary care cost £407.65 for each patient. Financial incentives, abridged questionnaires and pre-notification had a positive effect on retention rates. Conclusion: The recruitment studies included showed differences in strategies, clinical settings, mental health conditions and study design. It is difficult to assess the overall effectiveness of any particular recruitment strategy as some strategies that worked well for a particular population may not work as well for others. Paying attention to the accessibility of information and consent materials may help improve recruitment. More research in this area is needed given its important implications.