Interventions in health or social care are often complex for a variety of reasons. This complexity may be in the intervention itself. The intervention may have multiple components, target a range of behaviours, involving a range of practitioners with different expertise and skills for delivering the intervention. The people receiving the intervention may have differing requirements, so the intervention may need to be flexible or individually tailored. There may be flexibility, not just in intervention delivery, but also acceptance and adherence by participants. The intervention may target a number of groups, settings or levels in society (from the individual level to the whole of society). Complexity may also arise in the context in which the intervention is implemented, and how it is conceived, developed and evaluated. Complex interventions can be considered as events in systems, when the systems themselves are complex, adaptive and in continuous change.

This complexity makes intervention development and evaluation challenging. However, excellent guidance is available from the Medical Research Council’s (MRC) framework for developing and evaluating complex interventions. The framework divides complex intervention research into four phases: development or identification of the intervention, feasibility, evaluation, and implementation. A research project can start at any of these phases, depending upon what has been developed previously and a phase may need to be repeated or re-visited according to need and preceding findings. Each of these phases has core elements, which include a consideration of contextual factors, programme theory, stakeholders (especially patients and the public), key uncertainties, intervention refinement and economic considerations.

The phase developing or identifying a complex intervention often involves systematic reviews of evidence, development of programme theory and co-production with patients, members of the public and other key stakeholders.
The feasibility phase involves not only an assessment that the intervention is acceptable and possible to implement, but also that the methods used for a future evaluation are feasible such as recruitment and retention to a randomised controlled trial, randomisation method and outcome measurement.

The evaluation phase not only assesses the effectiveness of the intervention compared with usual care often in a pragmatic randomised controlled trial, but also its value for money or cost-effectiveness in an economic evaluation, and whether it was implemented as planned in a process evaluation, including qualitative research or mixed methods

The implementation phase determines whether the intervention can be widely adopted in real world settings. Implementation outcomes not only include the reach or uptake of services, but also the implementation strategy and contextual factors that act as barriers or facilitators.

The development and evaluation of complex interventions involves a wide range of health service research methods. Within the ARC North West Coast Methodological Innovation, Development, Adaptation and Support (MIDAS) theme, the complex intervention sub-group can be seen as cross-cutting across all of the other sub-groups: behavioural science, clinical trials, evidence synthesis, health economics, health equity, implementation science, information science, medical statistics, public engagement and qualitative.

Reference
Skivington K, Matthews L, Simpson SA, Craig P, Baird J, Blazeby JM, et al. A new framework for developing and evaluating complex interventions: update of Medical Research Council guidance. BMJ 2021;374:n2061 http://dx.doi.org/10.1136/bmj.n2061

Nefyn Williams.
Zara Quigg
Greg Irving

• Greg Irving at ARCFEST
–Slides
–Presentation

• Joe Langley’s presentation on co-design, 10/02/2022.
• Grahame Smith’s presentation on Living Labs, 03/05/2022.