Miller & Moyers’ paper, ‘The Forest and the Trees: Relational and Specific Factors in Addiction Treatment’, argues that, currently, a focus on the ‘trees’ (specific factors, i.e. specific treatment content) acts to the detriment of examining the ‘forest’ (relational factors, i.e. the larger interpersonal context in which treatment is delivered) 1. The title chosen by the authors evokes the proverbial challenge of not being able to see the forest for the trees, but the authors suggest some additions to existing methodology that would enable researchers to look at both types of variable. In particular, they make the case for specifying and studying these ‘non-specific’ or relational factors. However, from an alternative perspective, specifying ‘non-specific’ factors in the way that Miller & Moyers suggest may actually be creating more trees, instead of enabling a ‘forest’ view. Factors such as therapist interpersonal skills and treatment fidelity, which the authors highlight as modifiable relational factors, have, to date, been targeted through a mechanism very similar to that used for ‘specific content’, e.g. through therapist training [2-4]. In other words, as soon the non-specific factors are specified and practitioners trained accordingly, they can be treated in the same way as specific factors, hence becoming more ‘trees’. Miller & Moyers conclude: ‘as relational influences on outcome come to be better understood, they can be specified, measured, implemented in treatment, tested, and incorporated into the training of the next generation of addiction professionals’. Would this require a fundamental shift in research methods? Arguably not. Observational analyses in existing clinical trials could be used to generate hypotheses regarding these relational factors. Once identified, presumably the next step would be their implementation in treatment, testing via trials, and then incorporation in meta-analyses. However, Miller & Moyers argue that: ‘aggregation of findings—whether across participants in a study, sites within a multisite trial, or trials within a meta-analysis—masks variability in outcomes that may hold important clues to underlying mechanisms’. Such a statement risks painting a false dichotomy between aggregated findings and the investigation of relational factors. In meta-analyses some variation will always exist, whether due to chance or to differences in trial context or content 5, 6. On its own, variance in a meta-analysis does not de-legitimize that meta-analysis, nor does it necessarily mask key causes of variation. Indeed, once these relational factors are specified, measured and tested in the same way in which specific factors are currently dealt with, meta-analyses of the trials of these new tests would still be subject to variation in outcome due to remaining unspecified factors. Miller & Moyers are right to point out that, in focusing exclusively on specific factors related to treatment content, research into addiction treatments may be overlooking important relational factors and their associated effects. However, in acknowledging genuine and measurable causes of variation—more trees, arguably—it is important that a true forest view is not obscured. Using existing methodology, findings can be aggregated without masking the impact of underlying mechanisms, as long as these potential mechanisms are identified in advance. Relational factors that can be measured empirically and in which therapists can be trained can be tested in randomized controlled trials, as has recently been done with empathy in the context of physician training 7, 8. Such trials could then be aggregated in meta-analyses. Even where not tested directly, the contribution of these relational factors could be examined in systematic reviews through meta-regression, as has already been performed with specific factors 9, 10. The trees and the forest can both be taken into account, but it is important not to lose sight of which is which. None. J.H.-B. receives funding from the National Institute for Health Research School for Primary Care Research (NIHR SPCR). The views expressed in this research are those of the author and not necessarily those of the NHS, the NIHR or the Department of Health.
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