Benefits of Participation in Clinical Trials: An Umbrella Review Bouzalmate Hajjaj, Amira Massó Guijarro, Paloma Saeed Khan, Khalid Bueno Cavanillas, Aurora Cano Ibáñez, Naomi Participation Non-participants Systematic reviews Umbrella review Health changes Randomised controlled trial Participation in randomised clinical trials (RCTs) entails taking part in the discovery of effects of health care interventions. The question of whether participants’ outcomes are different to those of non-participants remains controversial. This umbrella review was aimed at assessing whether there are health benefits of participation in RCTs, compared to non-participation. After prospective registration (PROSPERO CRD42021287812), we searched the Medline, Scopus,Web of Science and Cochrane Library databases from inception to June 2022 to identify relevant systematic reviews with or without meta-analyses. Data extraction and study quality assessment (AMSTAR-2) were performed by two independent reviewers. Of 914 records, six systematic reviews summarising 380 comparisons of RCT participants with non-participants met the inclusion criteria. In two reviews, the majority of comparisons were in favour of participation in RCTs. Of the total of comparisons, 69 (18.7%) were in favour of participation, reporting statistically significant better outcomes for patients treated within RCTs, 264 (71.7%) comparisons were not statistically significant, and 35 (9.5%) comparisons were in favour of non-participation. None of the reviews found a harmful effect of participation in RCTs. Our findings suggest that taking part in RCTs may be beneficial compared to non-participation. 2022-12-13T10:08:28Z 2022-12-13T10:08:28Z 2022-11-21 journal article Bouzalmate-Hajjaj, A... [et al.]. Benefits of Participation in Clinical Trials: An Umbrella Review. Int. J. Environ. Res. Public Health 2022, 19, 15368. [https://doi.org/10.3390/ijerph192215368] https://hdl.handle.net/10481/78417 10.3390/ijerph192215368 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI