Assessing fidelity to Motivational Interviewing in Public Health Interventions (MI-PHI)

Principal / Lead investigator
Co-investigators / research team
Type of study

Qualitative study


Systematic reviews and meta-analyses have shown small to medium effects of Motivational Interviewing (MI) across a range of settings including, but not limited to, smoking cessation, alcohol use, chronic disease, HIV counselling and maternal and child health services.

Public health interventions aimed at promoting uptake of healthy behaviours often involve well-developed content and materials. However the most effective clinical method of delivering these programmes is often less well articulated. Elements of MI, a patient-centred approach that aims to help patients resolve ambivalence about behaviour change, have been integrated into public health interventions, collectively referred to as MI-based interventions.

However, evidence from pragmatic trials reveals a mixed picture of the effectiveness of MI-based interventions in everyday clinical practice.

One explanation for the variability in effect is the fidelity with which an intervention is delivered. MI is itself a complex intervention and, when it is added to a complex public health intervention, fidelity of MI can be challenging to assess. Among the existing validated measures of MI, there is no fidelity measure able to isolate the elements of MI integrated into these public health interventions. This limits our understanding of the variability of findings and also limits our ability to isolate and test theoretically derived hypotheses of active mechanisms resulting in change. Understanding the mechanisms of action of complex behaviour change interventions, such as Motivational Interviewing, is critical to replicate intervention effects, eliminate superstitious elements of intervention delivery and to ensure efficient training of clinicians.  

The overall aim is to develop a process evaluation method of MI fidelity, by reliably assessing when and how clinicians establish a behavioural focus against which to strategically elicit and reinforce change talk.

Who is the study sponsor?

Cardiff University


Wellcome Trust ISSF Public Health Collaborative Awards (Cardiff University)

Total grant value


Start date


End date


How could this research potentially benefit patients?

The broad question driving this work is: why has MI not worked to effect change in public health interventions? By seeking to answer this question we are looking to assess reliably MI fidelity and to isolate MI techniques so that the effect of these might be more precisely evaluated in future trials, including applications in complex behaviour change interventions in children and adolescents, aligned with the DECIPHer research programme. 

Outputs generated (Reports / Publications / Impact)

Details to follow