Cohort studies generate and collect longitudinal data for a variety of research purposes. Randomised controlled trials (RCTs) increasingly use cohort studies as data infrastructures to help identify and recruit trial participants and assess outcomes.

To examine the extent, range and nature of research using cohorts for RCTs and describe the varied definitions and conceptual boundaries for RCTs using cohorts.

Scoping review.

Searches were undertaken in January 2021 in MEDLINE (Ovid) and EBM Reviews—Cochrane Methodology Registry (Final issue, third Quarter 2012).

Reports published between January 2007 and December 2021 of (a) cohorts used or planned to be used, to conduct RCTs, or (b) RCTs which use cohorts to recruit participants and/or collect trial outcomes, or (c) methodological studies discussing the use of cohorts for RCTs.

Data were extracted on the condition being studied, age group, setting, country/continent, intervention(s) and comparators planned or received, unit of randomisation, timing of randomisation, approach to informed consent, study design and terminology.

A total of 175 full-text articles were assessed for eligibility. We identified 61 protocols, 9 descriptions of stand-alone cohorts intended to be used for future RCTs, 39 RCTs using cohorts and 34 methodological papers.

The use and scope of this approach is growing. The thematics of study are far-ranging, including population health, oncology, mental and behavioural disorders, and musculoskeletal conditions.

Authors reported that this approach can lead to more efficient recruitment, more representative samples, and lessen disappointment bias and crossovers.

This review outlines the development of cohorts to conduct RCTs including the range of use and innovative changes and adaptations. Inconsistencies in the use of terminology and concepts are highlighted. Guidance now needs to be developed to support the design and reporting of RCTs conducted using cohorts.

According to the Medical Research Council (MRC) framework, the theorisation of how multilevel, multicomponent interventions work and the understanding of their interaction with their implementation context are necessary to be able to evaluate them beyond their complexity. More research is needed to provide good examples following this approach in order to produce evidence-based information on implementation practices.

This article reports on the results of the process evaluation of a complex mental health intervention in small and medium enterprises (SMEs) tested through a pilot study. The overarching aim is to contribute to the evidence base related to the recruitment, engagement and implementation strategies of applied mental health interventions in the workplace.

The Mental Health Promotion and Intervention in Occupational Settings (MENTUPP) intervention was pilot tested in 25 SMEs in three work sectors and nine countries. The evaluation strategy of the pilot test relied on a mixed-methods approach combining qualitative and quantitative research methods. The process evaluation was inspired by the RE-AIM framework and the taxonomy of implementation outcomes suggested by Proctor and colleagues and focused on seven dimensions: reach, adoption, implementation, acceptability, appropriateness, feasibility and maintenance.

Factors facilitating implementation included the variety of the provided materials, the support provided by the research officers (ROs) and the existence of a structured plan for implementation, among others. Main barriers to implementation were the difficulty of talking about mental health, familiarisation with technology, difficulty in fitting the intervention into the daily routine and restrictions caused by COVID-19.

The results will be used to optimise the MENTUPP intervention and the theoretical framework that we developed to evaluate the causal mechanisms underlying MENTUPP. Conducting this systematic and comprehensive process evaluation contributes to the enhancement of the evidence base related to mental health interventions in the workplace and it can be used as a guide to overcome their contextual complexity.

ISRCTN14582090.

Precision medicine approaches to obesity aim to maximise treatment effectiveness by matching weight management interventions (WMIs) to characteristics of individuals, such as eating behaviour traits (EBTs). Acceptance and commitment therapy (ACT)-based WMIs may address EBTs such as emotional and uncontrolled eating more effectively than standard interventions, and might be most effective in people with high levels of these traits. However, few studies have examined this directly. We will examine (a) whether ACT-based interventions are more effective for people with certain levels of EBTs (ie, moderation) and (b) whether ACT-based interventions operate through changes in EBTs (ie, mediation).

This individual participant data (IPD) meta-analysis will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses of Individual Participant Data guidance. We will include studies on ACT-based WMIs that assessed EBTs in people with a body mass index ≥25 kg/m². We identified studies by screening studies included in a previous review of third wave cognitive behavioural interventions, and updating the search to 20 June 2022. We will request IPD from eligible published and unpublished studies. We will harmonise and re-analyse data using a two-stage random effects meta-analysis pooling within-trial interactions to investigate moderating effects and using a one-stage simultaneous equation model to examine mediating effects. We will assess the risk of bias in included studies using the Cochrane Risk of Bias tool 2 and the Risk of Bias in Non-randomised Studies of Interventions tool.

Ethical approval has been obtained from the Cambridge Psychology Research Ethics Committee (Application No: PRE.2023.121). Data sharing will follow data transfer agreements and coauthorship will be offered to investigators contributing data. Findings will be disseminated through peer-reviewed journals and conferences and will contribute to the lead author’s PhD thesis.

CRD42022359691.