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Unpacking the ‘Black Box Of Horrendousness’

23 June 2022

How can we address the challenges of conducting trials with adults with impaired capacity to consent?

Anyone who has been involved in developing or conducting trials involving people who are unable to provide their own consent to take part (or who has been around researchers involved in these trials) will recognise the challenging nature of these trials. Unfortunately, these challenges often lead to populations with impaired capacity to consent being excluded from trials. Whilst the challenges are widely acknowledged in the research community, until now neither the nature of these barriers, nor ways to overcome them, have been identified.

As part of the larger CONSULT project, we conducted a qualitative study (CONSULT-ENABLE) to explore researchers and healthcare professionals’ views about the barriers and facilitators to conducting trials with adults lacking capacity to consent. We interviewed 26 researchers and healthcare professionals with experience in a range of different roles, trial populations and settings across the UK in order to get a broad perspective. This included research nurses, trial managers, chief investigators, and other research team members.

Barriers and facilitators occur at different stages of a trial

Researchers described a number of barriers to conducting trials involving adults lacking capacity and outlines strategies they used to overcome them. These occurred at key stages in the design and conduct of the trial, including when making trial design decisions, navigating the process for obtaining ethical approval for the trial, assessing a participant’s capacity to consent to a trial, identifying and involving alternative decision-makers (consultees and legal representatives), and when revisiting consent during a trial.

They were grouped into three themes: 1) the perceived and actual complexity of trials involving adults lacking capacity, 2) importance of having access to appropriate support and resources, and 3) need for building greater knowledge and expertise to support future trials.

Diagram of key stages and themes

Trials involving adults lacking capacity are challenging and complex

Participants described trials involving adults lacking capacity as challenging. The legal frameworks and research governance process acted as a barrier to conducting trials, particularly when research teams had little or no experience in this area. For some, the concern about getting it ‘wrong’ impacted on how decisions were made about the inclusion adults of lacking capacity.

“As a researcher it feels like just an insurmountable black box of horrendousness that I dare not go. It feels very much [that] if you get this wrong you will be illegal … and the ethics police will come for you or something”

Need for greater support

Having public involvement throughout the trial was important, and using data from qualitative or feasibility studies to inform the trial design was also seen as beneficial. It was also important that tailored information and decision support was provided to participants and their families, and effective communication occurred between members of clinical and research teams. However, a lack of access to information and support about how to design and conduct trials involving adults with impaired capacity was considered to be a significant barrier.

“I’ve been stabbing in the dark like ‘where should I look for reliable information’? A lot of it was potluck

Recommendations to address the challenges

Alongside recommendations for future research, we have made a number of practical recommendations for specific stakeholder groups including funders of health and care research, research ethics committees, research governance and infrastructure leads, trialists, and research staff who recruit participants. This includes the need for adequate resourcing of trials involving adults with impaired capacity, the need for greater consistency in ethics reviews, ‘designing in’ flexibility in consent processes, and system-wide initiatives to build capacity and competence in research involving adults lacking capacity.

Diagram of key recommendations

Further work is ongoing to develop resources to help support researchers, including a website which collates information about research involving adults lacking capacity and the development of the INCLUDE Impaired Capacity to Consent Framework.

Published article

The full findings from CONSULT-ENABLE study are available at: Shepherd, V., Hood, K. & Wood, F. Unpacking the ‘black box of horrendousness’: a qualitative exploration of the barriers and facilitators to conducting trials involving adults lacking capacity to consent. Trials 23, 471 (2022).

A summery of the key findings and recommendations is available on the CONSULT webpage.


CONSULT is an NIHR Advanced Fellowship funded by the Welsh Government through Health and Care Research Wales.