Distribució de les llars segons el sexe de la persona sustentadora prin- prin-cipal a l’Estat espanyol (2006-2017)

As we have seen in Chapter Two behavioural treatments, such as behavioural activation (BA) and behavioural activation for depression (BATD) are theory-driven collaborative treatments with randomised controlled trial evidence to support their implementation. The considerable mismatch between the prevalence of depression and the availability of evidence-based psychological treatments outlined in Chapter One creates significant problems for society (Centre for Economic Performance's Mental Health Policy Group 2006). In health care systems such as the National Health Service (NHS), behavioural therapy may offer the possibility of meeting some of this demand due to its single-strand nature (Lovell and Richards 2000) and simplicity. While the evidence cited in support of such propositions is attractive, it is far from definitive as it is in narrative reviews (Jacobson and Gortner 2000) that may only provide a selected section of the overall picture and can be misleading to the reader (Glanville and Sowden 2002).

In order to counter these problems and develop a clear picture regarding the effectiveness of an approach all available evidence should be reviewed.

This process, termed systematic review, uses clearly predefined protocols to generate balanced inferences using all available evidence (Glanville and Sowden 2002). Systematic reviews, in contrast to narrative reviews, have the following characteristics (Higgins and Deeks 2008): they

 Clearly state a set of objectives with pre-defined eligibility criteria for studies;

 Use an explicit, reproducible methodology;

 Deliver a systematic search that attempts to identify all studies that would meet pre-defined eligibility criteria;

 Offer an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias;

 Produce a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

Behavioural therapy has been included as a comparator in a number of systematic reviews that evaluated the effectiveness of CBT compared to other therapies (Churchill et al. 2001, Dobson 1989, Gloaguen et al. 1998).

Initial searches were conducted in the Database of Reviews of

Effectiveness (DARE) and the Cochrane Database of systematic Reviews.

No systematic reviews were found that had examined BT/BA as the primary intervention against which other therapies were compared. The first step to conducting a comprehensive review of a clinical question is to ensure that such a body of work does not already exist that is suitable for updating (Glanville and Sowden 2002). The reviews cited above were not capable of providing a comprehensive overview of all trials using

behavioural therapy, as the search terms used would have been designed to examine the subject areas addressed specifically in those reviews, such as cognitive therapy (Dobson 1989, Gloaguen et al. 1998) and brief

psychological therapy (Churchill et al. 2001). This would therefore be problematic if we were expecting those reviews to provide a

comprehensive picture of behavioural therapy (and/or BA). Searches would not identify studies specifically examining behavioural therapy where it was not indexed using „brief therapy‟ or „CBT‟ or associated terminology.

Another potential problem of using those reviews looking at CBT for the purposes of this research was that they were relatively old and not

conducted using the most up-to-date guidance on review design (Moher et al. 1999, Moher et al. 2009). Study selection would not have been related to the specific objectives of examination of the effectiveness of behavioural therapies of depression, so that even if a highly sensitive search strategy identified relevant studies, the review methodologies may not have

included them. If such reviews were to be used as the basis of this research they would therefore potentially introduce bias at the first stage. In

summary, while reviews up to the date of our work had used behavioural therapy as a comparator, relying on them would be problematic. They would potentially introduce bias and methodological limitations.

Considering these limitations it was decided that a sufficiently rigorous examination of the effectiveness of behavioural therapy had not been conducted upon which appropriate primary studies could be designed. It

was therefore decided that a new systematic review of the evidence, focussing on the effectiveness of behavioural therapies in the treatment of depression, was required. The review would collate all empirical

information linked to a research question via a clear pre-determined systematic approach and provide an evidence synthesis. This would minimise bias and produce a reliable estimate of the effectiveness of behavioural therapy in its own right, which could be used to inform future research based upon gaps in knowledge (Higgins and Deeks 2008).

This chapter outlines the methods used to conduct a systematic review of evidence regarding the effectiveness of behavioural therapy for depression and discusses its findings. This approach was used to contribute new knowledge regarding behavioural therapy and highlight any gaps in the evidence base. This was related to the issues summarised in Chapters One and Two of the prevalence of depression, limited access to effective psychological interventions and the potential of BA as a single-strand intervention to fill some of that gap. The review follows a transparent process to appraise and summarise all randomised controlled trials, with effectiveness explored where possible via meta-analysis. Meta-analysis provides a statistical approach to combining the results from a number of studies exploring the same construct, in this case change in level of depression symptoms. It provides a natural extension of a systematic review following the logical process of gathering all the evidence in a specific area, reviewing and appraising the quality of studies and

combining overall findings. It thus provides a comprehensive picture of the true effect of an intervention compared to a particular comparator. Through its combining of study results, meta-analysis increases the precision of estimates of effectiveness of an intervention, since often individual studies may be too small and underpowered to differentiate true difference from chance findings (Moher et al. 1999). Meta-analysis increases such power, and hence the chance that observed effects of an intervention are correctly assessed. A consistency of effects from studies in differing populations or environments can be observed which is not possible through the use of an individual study or narrative reviews. This provides a more scientific

approach to exploring possible reasons for inconsistency across primary study findings, if present, as potential moderators of effect can be explored within meta-analysis. Therefore in this research a well-conducted and transparent systematic review combined with a detailed meta-analysis was used to improve statistical power, often a problem in psychotherapy trials, and produce a broader understanding of the potential benefits which behavioural therapy for depression might offer.