Evaluation and validation of social and psychological markers in randomised trials of complex interventions

The general public is exposed through the media to countless claims concerning the efficacy of counselling and various forms of psychotherapy for the treatment of depression and other mental health and personal problems. Health service providers are under increasing pressure to increase the availability of counselling and psychotherapy. There is clearly a need to design and implement controlled clinical trials to test whether these therapies work. It is equally clear that we need to develop and implement research projects that can tell us how these therapies work, what are the sources in the variability in responses to therapy and how these might be manipulated so that the therapies can be refined and improved. Equally, if a particular form of therapy does not appear to be very effective, we can use the same sources of information to develop an improved version that might be.

This is a proposal for the development, evaluation and dissemination of statistical and econometric methods for the design of explanatory trials of psychological treatments and the explanatory analysis of the clinical and economic endpoints arising from these trials. We are concerned with making valid causal inferences about the mechanisms of treatment-induced change in clinical and economic outcomes. The present project is focussed on the use of social and psychological markers to assess treatment-effect mediation. The proposed programme of work has three integrated components: (1) the extension of instrumental variable methods to latent growth curve models and growth mixture models for repeated measures data, (2) the development of designs and meta-analytic/meta-regression methods for parallel trials, and (3) the evaluation the sensitivity/robustness of findings to the assumptions necessary for model identifiability. A core feature of the programme will be the development trial designs of involving alternative randomizations to different interventions targeted on specified mediators.