Readers of this News Blog know that CLAHRCs are interested in behaviour change – CLAHRCs not interested in this subject should send the money back! So a recent special issue of Psychology and Health on the risk of bias in RCTs of behaviour change interventions should pique our interest. Unsurprisingly, much of the material is old hat to clinical and service delivery researchers, and the issues discussed are not specific for behaviour change interventions. Drug trials are the exception in not having to cope with difficulties such as in blinding therapists (leading to co-intervention or contamination), blinding patients and observers (leading to detection bias for subjective outcomes), and isolating or standardising the active ingredient of the intervention. The above problems are shared with trials of most types of intervention; surgery, physiotherapy, targeted service change, generic service change, and so on. One author conflates randomisation (a procedure to guard against selection bias) with other procedures, such as double blinding (which guards against performance and detection bias). In fact, they are separate causes of bias and it is possible to have one without the other.
If you have time for only one article, I recommend the paper by Jim McCambridge  on the social psychology of research participation. This includes question-behaviour effects where consent procedures or outcome questionnaires (applied to control and intervention groups) interact with the intervention to attenuate or amplify its effects. To deal with this, they recommend the Solomon-4 design where randomisation is to both intervention and (enhanced) questionnaires in a 2×2 factorial design. A real example where filling in a lengthy questionnaire interacted synergistically with an intervention is given. McCambridge makes the excellent point that the problems don’t go away just because a study is not randomised. The article, however, also deals with randomisation itself. Being assigned to a control group might be associated with ‘resentful demoralisation’. Here Zelen randomisation (no consent from control group) is one possibility. Another, oft recommended by the CLAHRC WM Director, is ensuring that only patients in equipoise  enter a trial, as originally recommended by Brewin and Bradley.
— Richard Lilford, CLAHRC WM Director
- Tarquinio C, Kivits J, Minary L, Coste J, Alla F. Evaluating complex interventions: Perspectives and issues for health behaviour change interventions. Psychol Health. 2015; 30(1): 35-51.
- McCambridge J. From question-behaviour effects in trials to the social psychology of research participation. Psychol Health. 2015; 30(1): 72-84.
- Lilford RJ, Jackson J. Equipoise and the ethics of randomization. J R Soc Med. 1995; 88(10): 552-9.
- Brewin CR, Bradley C. Patient preferences and randomised clinical trials. BMJ. 1989; 299(6694): 313-5.