In September 2026, we published the updated Cochrane Methodology Review of studies of strategies to improve recruitment to randomised trials. This adds 53 new studies to the total of 91 eligible studies, providing 94 comparisons and involving more than 175,000 participants. Eighty‐one studies involved strategies aimed at trial participants and 10 evaluated strategies aimed at recruiters. A total of 65 recruitment strategies were tested, with 49 evaluated in a single study. The following five strategies were supported by high‐certainty evidence:

• Open‐label trials versus blinded, placebo trials
• Telephone reminder versus no telephone reminder
• Recruitment primer letter versus no letter
• Multimedia information via a digital link/QR code plus paper participant information leaflet versus paper leaflet alone
• Optimised, user‐tested participant information leaflet versus standard leaflet

Click here for the full review.
 

In November 2024, we published the substantially updated Cochrane Methodology Review of studies of publication bias, covering both non-publication of results and time to publication. This replaces two earlier review and it includes a total of 204 research reports tracking 165,135 trials. The review shows that just over half (53%) the trials were published in full. The median time to publication was approximately 4.8 years from the enrollment of the first trial participant and 2.1 years from the trial completion date.

Click here for the full review or here for the lead author's 🎧 audio summary 🎧.